Good morning and welcome to this lecture in our course on chemical engineering principles of C V D processes. In the last few lectures we have been looking at various types of C V D processes and reactors, various conditions of pressure, various patterns of temperature distribution in the reactor and various types of films that we deposit on substrates. So today we are going to talk about methods of measuring properties of C V D films. Why do we need to measure the properties of C V D films? There was actually a saying I think it was by Lord Kelvin who invented the Kelvin temperature scale. He said what you do not measure you cannot control. It is an interesting statement. He is what he is saying is that unless you are able to measure something you cannot guarantee either its quantity or quality. Typically to guarantee the quantity you have to be able to do quantitative measurements and in order to guarantee quality you have to be able to do qualitative measurements. And so when you talk about C V D films both types of measurements have to be applied. There are certain properties of the film that we need to be able to characterize in a qualitative manner and certain properties that we need to quantify. Also there are certain properties that are functional what the film is supposed to do for you that has to be measured whereas there are some properties which are less direct and these indirect measurements however have a large role to play in terms of process control and optimization and ensuring that we get the functionality that we are looking for. Now when we do measurements in general you can classify them in two ways that are what are known as in situ measurements and exit to measurements also called online measurements and offline measurements and in situ or online measurement has the huge benefit that the data are being measured in real time. So as you process wafers and they are going through with a film being deposited on them you take the measurement right there and so you have visibility into what is going on with the process virtually at any instant in time whereas an exit to or offline measurement is as the name suggests done remotely. So typically every shift in a manufacturing line you would take a sample you would take it to a laboratory and subject it to various types of analysis. Now the downside of such measurements is there is a time lag so by the time you take the samples by the time you do the measurements by the time the data comes back you would have processed many more lots of wafers or other products. So if you detect a problem in your offline test everything that you have produced between the time you took the sample and the time the data came back would be compromised and so you do not have that real time feedback. So that is the biggest downside. The upside though is that the offline measurements can frequently be done using much more sophisticated instrumentation the readings can be much more precise much more accurate and can yield much more detailed information about whatever you are trying to inspect. So they do have you know pluses and minuses what you really need then is a combination of the two. So typically in CVD industry both types of tests are employed there will be a series of in situ tests which typically will provide quick data mostly quantitative which can be used to essentially derive process control charts and put in you know SPC methodology six sigma methodologies and all that to ensure that you maintain the quality of the output. In addition you will be simultaneously doing offline testing on the same CVD films to look for more detailed characteristics for example the structure of the film. It is not easy to do that online although now there are online XRDs that can give you a brief snapshot of how crystalline the structure is but if you want a more detailed for example sectional profile of the film to see how the composition is changing across the thickness of the film you cannot do that online. So a good combination of both types of measurement methodologies provides the most value both for the producer as well as the customer. Another way to classify measurements in such instances is the direct versus indirect. Now when you say direct measurement what we mean is the reason you are realizing a CVD film on a substrate is for a certain purpose. We have looked at several of them you know it could be to provide conductivity variations could have a conducting film, semi conducting film, dielectric film or it could be for completely different purposes maybe to provide thermal protection or moisture barrier capabilities or it could be corrosion protection, erosion protection, wear protection, galling I mean there are many many reasons why CVD films are put down on surfaces. So the most direct test would obviously be one that test the purpose for which the CVD film was put down. I mean if you are putting it down to achieve a certain conductivity at a location obviously the most logical test to do is to measure the conductivity there and see if you have realized your objective and from a customer view point that is really what they care about you know they do not care about what it takes to produce that film what they care about is are you able to deliver to their specifications and so the direct measurements are of most value to the customer who is using the product. Now this may not even be an external customer it could be an internal customer for example you could be making silicon wafers and part of the process may be chemical vapor deposition of a certain layer on the wafer and then it goes to the next step in the process. The next step becomes a customer for the previous step right. So when I say customer do not think of external customers it can also be an internal customer may be just your the division next door but they would expect certain properties of this product that you are making. So you know obviously conductive measurements are easy to make. One thing that is different though when you are talking about CVD films I mean I am sure you have done conductivity, resistivity measurements in high school and college. The difference is of course with a CVD film you are looking for planar properties you are looking for sheet resistance properties planar conduction. So you have to be able to do essentially multi probe type of measurements in order to be able to measure not only the conductivity or resistivity at a single point but rather across a continuous plane of material. But apart from that many of the techniques you have already learnt to measure conductivity and so on are quite applicable here also. The other difference of course is that you are talking about measuring conductivity across a very thin film. So that requires certainly more precision particularly in the positioning of your probes. You want to be able to take the measurements only across a film and you know the probe should not for example touch the substrate. So the positioning to nano or micrometer resolution becomes important as far as keeping the probes on the surface and also sometimes you are interested in what are known as breakdown voltages. This is particularly important when you have an oxide film on a surface. You want to be able to tell how much of a voltage applied can the film support before it breaks down and allows for example conduction to happen. So this is called a breakdown voltage so essentially you will be testing conduction as a function of voltage and you keep increasing the voltage until you get to a point where there is a sudden sharp spike in the conductivity and that is where the oxide film basically breaks down. That measurement is important to A it can actually be used as an indirect characterization of thickness of the film because you can actually pre-calibrate this breakdown voltage or voltage as a function of thickness and using that you can use voltage measurements sorry current measurements for a given voltage as a measure of thickness. So that is one use. The other use is it is important to find out what is the breakdown voltage for a given thickness or the breakdown thickness for a given voltage so that you can ensure that the minimum thickness never falls below that value because you know if that happens you are going to have a catastrophic situation. The other type of measurement that is done uniquely for CVD films is called the, it is basically an electron mobility analyzer, Hall Effect analyzer and this provides more detailed instruction not only on the conductivity but also tell you the conduction paths that are present in your film. So if you have localized discontinuities in the film or defects in the film it can be used by making such measurements. Of course when there is the purpose of the CVD film is to provide protection to the surface for example coatings then the protection properties can be tested. If your CVD film is being placed on the surface to provide corrosion protection then you have to devise an appropriate corrosion test. So this could be something as simple as a environmental chamber where you put the substrate with the film into a temperature humidity chamber and cycle the temperature and the humidity through the specified values and look for signs of corrosion on the surface. It is an accelerated test for corrosion. The other way that corrosion is frequently tested with even more acceleration is what is called the salt spray test. So you take a solution of salt and spray it on the substrate and see if corrosion is initiated. So there are very specific corrosion tests typically developed by certification agencies like ASTM that specify exactly how the test is to be conducted and you can certainly conduct the test as specified. Similarly erosion testing. There are erosion testers and erosion test procedures, standards that have been defined and so you can take the substrate, mount it and subject it to various types of particle impaction for example and see if erosion develops and what is the rate of erosion for a given particle size, given velocity, given angle of impact and so on. So these are obviously functional properties that you are testing and this data when it is supplied to whoever is consuming the product is going to make them happy because they know that it is doing the job that it is supposed to. But as a CVD process engineer or equipment engineer you know that you do not have direct control over that property. What you have direct control over is the thickness of the film, the composition of the film, the uniformity of the film and so on which you can control by controlling the process parameters and the design of the equipment and the controls that you have on the process and so on. So you have to identify the controllable parameters in your process and start measuring them so that you can establish the required controls over these controllable parameters and deliver the required product quality to the customer. For example if I am trying to provide certain corrosion protection then I know that the way I am going to achieve that is by having a certain composition of film on the surface by having a certain thickness, by having a certain density, by having a certain level of impurities, by having a certain structure and so on. So I can list you know 7 or 8 process or product parameters which if achieved will enable me to achieve the functional specification on the product that I am making. So that is the next exercise that you have to go through and identify the critical parameters in your system. So when we look at a CVD film you know the things that obviously pop out in terms of important parameters to measure, indirect parameters right not the functional parameters but the indirect measurements. The key ones would be I would say the number one property that you would try to measure is thickness and structure. The third one is what is known as line width also critical dimensions. So what we mean by line width critical dimensions is if you have a substrate and you are trying to put down a film on top of it there is usually a pattern to the film. So you may have a certain thickness up to here and then the thickness may drop to 0 here and then again rise to a certain thickness later right. So in this particular case the line width as it is defined is the distance of separation between the two CVD films. The critical dimension is typically this and this, the length, the width and of course since this is 3 dimensional the height or the thickness of the CVD film. So these are the critical geometrical dimensions that you try to measure on a surface. So thickness even though that is listed separately is actually one of the critical dimensions that you want to be able to measure on the substrate. Composition is obviously very very important to know. You are trying to deposit a certain CVD film, you have to be sure that that is what you are depositing and that it is not some non-stalkometric film that you are depositing or something that is completely different from the chemistry that you are trying to achieve on the substrate. So the composition is important and then you know the surface properties particularly roughness can be a very important parameter to measure. When you have a substrate it has a certain predefined roughness but when you deposit a CVD film on it the roughness is going to change. That can be a very important parameter in many applications particularly when you are trying to provide a certain, if the film is trying to provide certain protection because a rough surface for example will erode very differently from a smooth surface. So the surface roughness becomes a very important parameter and impurity levels are also important to measure. You want to know how integral the film is both from a physical viewpoint as well as from a compositional viewpoint. The other parameter that we have mentioned previously is grain size. The grain size of a film to a large extent determines its strength, its durability, its permeability. Many of the properties that we try to achieve with a CVD film are actually leveraged very effectively by using grain size as a controllable parameter. What else? I mean we certainly have to look at properties like hardness, density. Another property that we had mentioned earlier is edge rate which is a good measure of how sustainable the CVD film is under aggressive environment. So I mean there is obviously a fairly long list of things that you can measure about a CVD film and where you stop really depends on you know again your process requirements and your customer requirements. The more demanding your customer is and the more high end the product is that your CVD film is going to go into typically the more measurements you have to do to ensure that the process stays under control. Whereas if you are making the CVD film for a mass production low cost type of device then you may choose to do only couple of these and say that as long as these stay in control I am going to assume that everything else stays in control. Again the primary way that you use these measurements you know it is not enough to measure and it is not enough to simply react to the measurement. A good manufacturing process will have a strategy in place where you look at not only whether a particular measurement is in spec or out of spec but you actually do some trend charts and make sure that the process is not showing signs of drifting out of control. Typically the type of charts that you would do are x bar range charts. So you would measure this as a function of time and there will be a mean for the process. There will be an upper spec limit, there will be a lower spec limit. So for example these could be thicknesses of the CVD film and you would want to have a specification on it that is let us say plus or minus 5% right. So you would have these spec limits and so your mean would essentially show some trend like this. So the first thing you would ensure is it stays within specs because if it exceeds the spec limit on either side you have to throw the product away. But more importantly in an you know enlightened 6 sigma factory what they will do is they will be also measuring the range. The range is the distance between max and min or sigma which is a standard deviation and that would also be monitored as a function of time and in addition to the spec limits control limits will be established UCL and LCL. The difference between a control limit and a spec limit is the specification limit is imposed by typically the customer or the product requirements. The control limit is derived from the behavior of the process. So typically the upper control limit would be set at x bar plus 3 sigma and the lower spec limit will be set at x bar minus 3 sigma and you would want to maintain your process within the control limits which should be tighter than the spec limits. So it provides you a safety band you know if you can control your process within the control limits the chances that you will have occasional excursions beyond the specification limit or significantly lower. So this SPC methodology is absolutely crucial to maintaining quality control over your product. So when people talk about 6 sigma quality right what they are talking about is this kind of methodology where you try to essentially maintain your process within plus or minus 3 sigma but the incorrect assumption here is that sigma over x bar is much smaller than 1. I mean this whole thing will you know break down if your standard deviation in the process is very high because then your x bar plus 3 sigma can actually exceed your upper control limit and x bar minus 3 sigma can exceed the lower control limit and in fact typically in a well behaved process the ratio of standard deviation to mean should not exceed 1 tenth okay. This parameter is called the variability coefficient and in a good process robust process that is running under well controlled conditions that ratio should never exceed 0.1 or 10 percent. If you do that then obviously your UCL and LCL are going to be much tighter than the corresponding USL and LSL and that is what you are aspiring for. Now this is good but there is even a level of quality control that is tighter than this and that says I do not care if my process is within the spec limits. I do not even care if my process is within the control limits. I do not want my process to drift from the mean as soon as I see even the smallest deviation from the mean where the process is supposed to run I am going to take action. So that is basically called trend chart analysis. So you do not wait for you know the readings to actually exceed one of these limits you watch the trend. For example if 6 consecutive measurements are one side of the mean you will probably think something is not right you know it is not a random statistical variation it is a systematic variation and then if that happens you have to tweak the process to bring it back to the center line. So this is actually called the Taguchi approach to quality it is called the Taguchi quality loss function. Taguchi was a famous engineer statistician who said that anytime the product measurement deviates from the mean or its ideal value it is losing there is a loss associated with it because the product is not as good as it can be. So he says anytime you see any deviation from the mean value treat it as a loss add up the losses and try to minimize that. So what he defines as quality loss function is the summation of all deviations from the process mean and he says in a good process that should be 0 or you should try to drive it to 0. In other words if you integrate and find the area between the trend line and the mean line that integral should be driven to 0 in your process that requires extremely tight process control I mean somebody has to be sitting there well not necessarily manually but at least you should have an ability to monitor how the process oscillates on a essentially a real time basis and provide a real time reaction to continuously keep bringing the process back to the mean. So that is kind of the ultimate in quality control methodology. Of course as you realize there is also cost associated with that because every time you tweak a process to bring it back to its ideal value somebody is taking some action there is an intervention involved there is a process disruption involved all of that is cost right. So that is a cost it is a cost of achieving quality and this is the cost of not having the quality and the 2 cost essentially must be added up to give a total cost to the manufacturer and you know the most enlightened approach is not to say that I am going to minimize this not to say that I am going to minimize the cost of tweaking what you should try to minimize is a total cost of this plus the cost of tweaking to avoid this right. So that is the new evolution in quality control theory that is being worked on and some interesting findings are coming out because of this you know in terms of what type of control methodologies are appropriate for what kind of processes okay. Anyway the whole point is out of this list of 10 or more parameters you have to identify which of these parameters is so critical that you apply this quality loss function methodology which ones are less critical and you can control them to control limits which ones are even less critical and you can control them to specification limits and which ones are so non-critical you do not even care you know you just take occasional offline measurements and as long as they show something good you are happy. So you have to go through the exercise of looking at all the measurable properties identifying ones that are truly critical for what you are trying to achieve with that CVD film and applying appropriate measurement technologies and control methodologies for specifically those properties. So that is all you know discussion about how you use your measurements but first you have to do the measurements right. So how do you measure CVD films? The most common inspection technique is what I mean suppose you are asked to you are given a CVD film and you are asked to measure it what would be the first thing you do any idea? No that is way down the list look at it look at it I mean the Cuban eye is one of the most sensitive detectors it is amazing what the eye can see that instruments cannot just like the human nose you know human noses can detect parts per trillion levels of things in the atmosphere there is no sensor that is ever going to be able to match the human nose in terms of its sensitivity you can try and get close but even nano sensors or pico sensors or femto sensors that people are working on you are never going to be able to match the human nose similarly you know human eye particularly from a trained operator you know if someone's job is to just look sit and look at CVD films on substrates as they are passing by it is amazing how sensitive they can become they can pick up very very minute variations which are very difficult actually to measure quantitatively using any known tools. So visual inspection is the number one thing you have to continuously watch the product and make sure that you know it looks good. So the first thing is always a visual check what is the second thing visually it looks okay what do you do next you can do one of two things you can look at it under different lights right so you can use bright light you can use UV light and see if something else shows up. So lighting is an enhancement so the lighting can be white light or UV light and so on typically bright light shows up metallic materials very well UV light will show up organics or fluorescent materials very well so that is a next enhancement so sometimes your eye cannot see things but with sufficient illumination it can see things and again the angle of illumination can play a role you can have incident angles that vary you can have light fixtures that kind of rotate around the specimen so that the illumination can be done in a 360 degree mode what is the next thing you can do still looking good you have looked at it you have looked it under light still looks okay what is the next thing you would think about doing magnification right. So that is where you start getting into microscope technologies because when you do microscopy even before you look at things like electron microscope you first do optical microscopy just provide some magnification magnifying lens magnifying glass typically 10x but nowadays there are optical microscopes that can give you 10000x magnification so that technology has certainly evolved to a point now that you are able to get fairly high magnifications but it is still going to be less than what you can get with an electron microscope. So what are the advantage why would you want to use an optical microscope if electron microscope can give you much higher magnification. The disadvantage of going to a higher magnification is that you look at less and less area right to take a wafer and inspect it using you know 1 micrometer or even 1 nanometer resolution is going to take you a very very long time whereas doing an optical magnification inspection at a lower magnification can be done much faster so certainly speed is much better you can cover a much larger fraction of the total area typically electron microscopic inspection can only be done on a small fraction of the surface and you assume that the rest of the surface looks similar whereas with an optical microscope and lower magnification potentially you can look at 100% of the surface so that has that advantage. The second advantage with optical microscopy again it is a quick and dirty test if there is some feature on the surface it will actually show up quite well when you do optical microscopy of course you will be using again lighting as an aid so you can do optical microscopy under bright light you can do it under UV light and so on it will show up different things it gives very good information on morphology. In other words by looking at a CVD film under an optical microscope you quickly get a feel for what it feels like what it looks like it is not going to give you detail information on the structure or on the dimensions but you will be able to tell is it a crystalline CVD film is it a nomorphous film is it well adhered to the substrate is there any evidence of sliding between the layers does it look like a pure surface or does it look like there are little impurities stuck in there. So that kind of high level information is very easy to gather when you do optical microscopy of course complexity cost all of these are issues that do not bother you when you are doing optical microscopy when you are doing electron microscopy first you need a trained operator you a person an untrained person cannot do it so you need to pay the person right you pay the person for the training that they have undergone to be able to use an electron microscope and secondly the equipment itself in an SEM scanning electron microscope the samples have to be prepared in a special way and they have to be mounted into a vacuum chamber and you have to have a source of high energy electrons and you have to have a way of collecting the scattered electrons and tracking them and measuring them and so on. So it adds cost and complexity and it requires a trained operator to perform whereas optical microscopy someone who is who you know does not even have high school education can be trained to do it and typically operators on manufacturing lines who inspect products using optical microscopes do come from that type of background but what they gain is experience once they have sat and looked at enough of the product they know what to look for and again their eyes get calibrated and they can actually pick up defects that even a sophisticated electron microscope cannot. So the optical microscope has several attractive features because disadvantage of course is the limitation in the magnification okay so let us say that you have done that now what is the next step do you immediately go to an electron microscope no because at this stage you really have to think about what you are seeing when you look at a CVD film or under an optical microscope you have to grasp what you are looking at are you seeing things that look let us say organic in nature or inorganic in nature are you seeing things that look particulate in nature or fibrous in nature or you seeing things that look like defects on the surface or asperities on the surface or impurities or contaminants on the surface. So you have to be able to make these kinds of qualitative decisions by inspecting the surface using an optical microscope and then based on what you decide your further inspection paths will deviate. For example if the optical microscope shows that you are mainly seeing inorganic materials and again the way you can tell that is by using different lights and different illuminations metal particles for example will show up very differently than non-metallic particles. So using an optical microscope it is possible to make their assessment. So the other possibility is it could be organic and what is the other possibility could be fibrous. So depending on what you think you see under the optical microscope you will then go to the next set of instruments that you use. For example if you think that you are predominantly seeing inorganic materials then you would certainly think about using electron microscopy whereas if you think it is mostly organic what would you choose? Any idea? How do you analyze organic materials on a substrate? Have you heard about infrared spectroscopy? So typically IR techniques, IR spectroscopy techniques will be used. If the material that you are seeing has a certain shape to it like for example it is fibrous then what do you do? You do not at that if it is that clear I mean if you know that it is fibrous then you do not even need to do additional analysis. You go look for sources of the fibers right. If the material can be identified quite clearly with an optical microscope there is no need to do additional inspection. Another thing you have to remember you know I said you cannot control what you do not measure. Another truism or saying is that inspection is not a value add activity. You have to minimize it. So any evaluations you do, measurements you do always keep in mind that the customer is not paying for this. It is coming out of your own revenue right. If you can do 0 measurements and still deliver high quality product that is ideal, not realistic. So you do have to invest in doing certain measurements to ensure that your process is in control but again you should always be driving towards minimizing it. It is absolutely extraneous cost. Your measurements are not what you ship to the customer. The product is what you ship. So all of your cost should go into making a good product and as little of it should go into how you measure it right and so it is important to identify exactly what tests need to be done and do no more and no less.  There is scanning electron microscopy, there is tunneling electron microscopy, there is OJ electron spectroscopy, there is secondary ion mass spectrometry, there is time of flight sims, there is you know there is a whole list of things that you could do or you could do simple solvent extraction and do chromatography. For example the inorganics are primarily ionic in nature. You take deionized water measure its conductivity and then extract the ions from the surface and measure the change in conductivity of the deionized water and that will tell you how much total ionic material there is on the surface. And similarly if it is organic material you have some decisions to make.  So again there is a battery of tests that you have to choose and decide which ones you want to run. And also you have to decide whether in terms of composition elemental composition is sufficient or you need to know the exact species. For example if you have a silicon oxide film if you simply do SEMEDX you know it will tell you that you have silicon and you have oxygen but it will not tell you that you have SiO2. For that you need to do additional tests to identify the actual composition of the species that it is SiO2 and not some SiXOY, right. So it is like peeling an onion. You start with the film and you slowly peel it and you stop when you have done enough peeling, right. That is kind of the general philosophy that you have to adopt. So when you talk about electron microscopy what are some of the considerations? How does electron microscope work?  So it is basically the simplest use of SEM is surface morphology characterization at high magnification and high resolution. And the difficulty within at the scanning electron microscope is that it is a time consuming and laborious process. You can only irradiate very very small portions of the substrate at one time. So to do a simple, if you take a CVD film that is even a few angstroms thick it can take you a day to do an analysis on it. So it is really not a good use of a person's time to sit and do this analysis. Nowadays they have these automated SEMs where you can essentially mount the sample and go home and it will do the analysis overnight and by the time you come back in the morning there is an automated stage where the sample will move incrementally every few minutes and the entire sample will be scanned and characterized by the time you come back. So these automated SEMs are now making it a little easier to use SEM analysis to characterize an entire surface. The SEM typically has a resolution of about 50 nanometers or so, 50 to 100 nanometers. If you want to improve it further then you use tunneling electron microscopy where the electrons instead of simply being scattered from the surface actually tunnel their way through the sample and they are detected at the other side. This improves your resolution to about 10 nanometers or so. So it is much better than using a SEM there are also high resolution SEMs and TEMs which a high resolution TEM can give you a nanometer resolution in sample analysis. Of course the drawback with TEM is it requires some special sample preparation. To prepare the sample for doing the TEM analysis takes much longer than the actual TEM analysis itself. You also have to mount the sample on a metal substrate. On the other hand in a scanning electron microscope because you are using high vacuum you cannot stick organic materials into an SEM. So if you want to have an SEM analysis of an organic film done you have to coat it with a metal usually gold is used gold is buttered on to the material and then you can stick it inside an SEM chamber. So the combination of SEM and TEM can certainly provide you with much better resolution but in order to get compositional information SEM and TEM are not going to do it. So you attach it to a EDS or WDS setup which is energy dispersive spectroscopic analysis or wavelength dispersive spectroscopic analysis which essentially use X-ray spectrometry of the signal to identify the actual elements that are present at that location. They have differences in their sensitivity. The wavelength dispersive is slower but has better resolution than EDS or energy dispersive spectroscopy. There are also differences in the minimum atomic number that I can detect. With the WDS you can detect up to beryllium whereas with an EDS you can detect up to fluorine F. So you can detect all elements heavier than fluorine or heavier than beryllium. Of course nowadays both EDS as well as WS apparatus is coming with what they call a carbon window which enables it to detect all the way down to carbon. So the range of atomic numbers that we can detect using SEM and EDS slash WDS is constantly being improved and up to carbon is now detectable. So SEM, TEM are certainly possibilities for analyzing samples. So under electron microscopy SEM and TEM are the most widely used. There is also a technique called OJ electron spectroscopy. OJ electrons are the electrons that are knocked off from the first layer when you irradiate a sample with an electron beam. OJ analysis therefore can be used for sectional analysis of a CVD film. So you would essentially continuously knock off electrons from various depths of the CVD film and do the SEM analysis and the EDS analysis and so on. So it gives you depth profiling capability. So that is a big advantage of OJ spectroscopy, it is spelt AUG or not OJ. The other method that is frequently used is SIMS which stands for secondary ion mass spectroscopy. Here essentially you are using ions to knock off secondary ions from the surface but the secondary ions are taken through a mass spectroscopy column where they are spectrally resolved to obtain the atomic masses of the individual elements. So this technique and another related technique called time of flight SEMS, TOF SEMS, they are kind of like OJ because they can give you this depth profiling but SEMS and TOF SEMS have better resolution than OJ spectroscopy. So if you want for example angstrom level resolution of a CVD film in terms of its elemental composition you use techniques like OJ, SEMS and TOF SEMS to be able to do that. Here so these are all methods that by the way there is another one called LAMA which stands for laser material mass analysis. This technique you essentially take the sample and you hit it with a laser and vaporize the entire sample. So you are not just doing knocking off of electrons, you are essentially vaporizing the sample and the vapors are then taken through a mass spectroscopic analysis and you detect the elemental composition. So all these techniques are good for looking at which elements are present but if you want to look at compositions in terms of products or species you have to use a different technique. Anybody know what is used to look for chemical species composition? NMR does not work for inorganics but for inorganic. So far we have been talking about inorganic materials, what is a good technique to use? ESCA anybody heard which stands for electron spectroscopy for chemical analysis which basically impinges the material with X-rays because X-ray scattering is a function of the molecular vibration levels and the molecular structure of the species that is present. So by using ESCA you can actually get species differentiation. So you can tell whether silicon is present as Si itself or SiO2 or Si3N4 right. So instead of just knowing that Si and N are present you know that they are present in the form of Si3N4. Obviously when you are making CVD films that is very important, you do not just need to know whether the elements are present, you need to know whether they are present in a particular stoichiometry. So ESCA is a workhorse particularly in the CVD industry and in fact as far as chemical speciation information is concerned, this is probably the only technique that works very well although certain types of materials can be analyzed by other means okay. So let us stop at this point and the next lecture will start with methods for analyzing organics on surfaces and then we will also talk about methods to measure thickness and so on. Any questions? See you at the next lecture.


Studio Ghibli's back with a brand new film called The Boy in the Heron. I took my son last night and we both had thoughts. Let's talk about him. The Boy in the Heron is PG-13. It's two hours and four minutes, according to IMDB. And my son and I didn't really care for it. And that hurts to say that stings. Now, if anybody's familiar with this channel, as of lately, you might notice, okay, he didn't really care for Boy in the Heron, which is currently sitting at 97% on Rotten Tomatoes. He also didn't care for Godzilla-1. Also at 97%, maybe 98%. I don't know. Yeah, I guess I'm the outlier in both of these. I didn't set out this year to have hot takes. In fact, I'd say for the most part, I'm pretty in line with the majority of movie critics, which isn't also a badge of honor by any means. I'm just giving my opinions and my thoughts on the movie as a whole. And that's what I'm going to do here. It's up to you to decide, hey, do I think this guy is being honest and do I think he's going to align with my thoughts? I'm just giving you what I saw and you can take that for what it's worth. It might not be worth anything and that's perfectly fine. That's acceptable. So this film, again, over two hours long, slightly, that's the problem right out of the gates. It's a bizarre movie, of course. It's by the guys that made Howl's Moving Castle, Spirited Away, Princess Mononoke. Two of the three I absolutely love. Spirited Away. I don't throw this word out often, but Masterpiece does truly come to mind when I think of that film. It's brilliant. It's breathtaking. The animation's top notch. And a lot of that stuff can be said about this new one, The Boy and the Heron. It looks gorgeous. Colorful as all can be. Beautiful animation, lovely voice work. We did see it with subtitles. That's fine. I'm sure you can find the English dub version in theaters as well. I don't know. The Wednesday showing we went to that was subtitles. The plot is loosey-goosey to go with the bird theme, which they do a lot in this film. It's about a boy. This will be spoiler-free. It's about a boy, hence the title, The Boy and the Heron, who loses his mother as the film starts. That's the centralized plot. His mom's gone to a fire, and he's going to be raised by this new woman four years later and his dad, who's never really around. He's a worker. He works for the military in a steel plant, doing a lot of the chassis's and different instrumentation weaponry needed to fight wars. This kid's fighting his own war, and that's the war of acceptance, of moving on. The thing I love about this kid is he's very resilient, he's knowledgeable, and he's able to do things on his own. He's self-sufficient. He builds tools. He learns how to conceal his emotions in front of people to stay strong and brave. He even, at one point, is willing to have... He's willing to inflict damage on himself so as he doesn't have to go to school and face more odds and more challenges. Now, I don't... Of course, I don't think anybody should inflict damage on themselves. My point is the kid does what he thinks he needs to in order to maintain his self-worth and to go on in life. As this movie progresses, it's going to get very slow for a very long portion of time. The middle of this movie suffers from its pacing so badly as the boy enters this mysterious world, a world within worlds with quirky characters and lovely visuals, and this heron is gonna be his guide on his misadventure to understand the truth about things and understand and forgive people in his life and learn to accept other people in his life. It has beauty, of course. It has amazing visuals. It has an amazing soundtrack. The music in this thing is fantastic. Voice work is fine. I'm trying not to be redundant. I can't remember what I said or not. I'm just kind of going off the hip. But what it really lacks, and this is the thing that hurts more than anything, is emotion. The emotion should be there, especially at the loss of a parent. I lost a parent, not much difference in age from this kid, so it really should have hit me in a special way than other people, and it didn't. It lingers on things that don't need to be lingered on and it pushes past things that should absolutely have focus.  As for my son, who's 11, this movie's way too vague. It's way too deep for him. It's too deep for me a lot of the times. I'm trying to listen, Spirit of the Way has tons of layer to it and I was able to pick up on those layers pretty well, I think, or at least interpret them in a way that felt comfortable and it felt, it felt good. In this movie, there's just so much to kind of dissect from scene to scene and you can really take what you want out of it, but the symbolism isn't that interesting and I don't really feel like digging that deep to understand all the complexities and the narrative that's going on because if it's not working from a surface level, if it's not engaging me enough at the top level, then I'm not willing to go any deeper for it. Now a lot of people will. Again, this is Studio Ghibli. They've done some amazing films. Most of their films I would say are works of art. They don't all work for me. I do love Kiki's Delivery Service for its slow pace and its whimsy, its childlike innocence. I didn't care for Princess Mononoke, which I know is a massive fan favorite. I thought the first half was really good, but then it just kind of, I don't know, like that one wasn't very deep at all. It was pretty obvious what was happening in that film. So I just, I was ready for the ride to be over. The Boy in the Heron is different because it really feels like it's almost a spiritual successor in some ways to spirit it away, but without all those magical elements that made that one so good. As for the characters, love the main child. The Heron's fun. He's interesting. And the second half introduces some characters that I think are hilarious. They're fun to look at. It's just really quirky in the best way possible. But again, it takes a long time to get there. And the second half felt so almost disconnected from the first half that it was like two different movies going on, fighting for attention. And at that point, I'm ready to leave. It's just too tedious. I think if this was a 90 minute movie, we'd have another very special film on our hands. But as it stands, it's just, it's just not for me. It's just mundane. And I wanted it to be done. Again, my son, who is a huge fan of not just this, but anime in general. He's a big anime guy. Loves reading the comics or the manga, whatever you call them. I'm not, anime is not my thing. Okay, I'll dabble in Dragon Ball Z on occasion. Throw in a, you know, you throw in a few different things and you'll get my interest. But I'm not sticking around for the long haul. I'm not watching 800 episodes or 1,000 episodes of One Piece or whatever that is. I do like these movies though. So this one hurts. This hurts me that again, it's like, oh, 97%. It's brilliant. It's genius. Is it though? Is it though? I question sometimes the motives of some of the critics out there, whether they just give everything a pass because it has a name associated to it, like an A24 movie or Pixar back in the day when they were untouchable.  And I just don't operate that way. It doesn't matter what name is associated to it. That might draw me in more. That might peak my interest more. But I'm not giving it a pass if I'm seeing in the theater feeling like I kind of threw my money away. And this time I did feel like that. You know, I draw money for my son. We had popcorn in the whole shebang and it just, my son actually turned me. He's like, how much is left? That's brutal. I don't want to hear that. I don't want to hear that. And I was thinking it too. All right. I'm not going to ramble any longer. Those are my thoughts on The Boy and the Heron. Of course, it gets all the production stuff knocked down to a T, visually beautiful, audio's gorgeous. I'm sure the soundtrack you could find at the score on Spotify or something and blast that bad boy and it would sound fantastic because those were definitely, definitely fantastic for me. Let me know if you saw this already or if you're interested or if I turned you off. Please don't let me sully your enjoyment or your opportunity to go see it. If you're a fan of the studio, again, Ron Tomatoes has this very high. If you take anything that site has with value, then you'll get something there. IMDb, I'm sure is scoring this well. I haven't looked yet. I was let down. Not when I would recommend. Maybe check it out in streaming. But again, just my thoughts. Let me know. Like the video if you had a good time. Please subscribe if you haven't. I post tons of movie reviews every single week. We'd love to have you stick around. If you really like what I'm doing, Patreon or YouTube join. The join button's right there. You hit it. You get access to exclusive videos. Same with Patreon. There's a $1 tier and that really helps the channel sustain itself. Helps me get motivated to keep doing this. All right. Thanks for watching. Hopefully I see you next time.


with Socrates and Sextus Empiricus and that's a long time ago and what they meant by skepticism was very different than what we mean by skepticism. They meant that you can't know anything. You can't know that the universe exists. You can't trust your senses because our senses lie and we're on these little creatures on a planet we're not set up to know everything. The thing is that agnosticism which was made up by Huxley at the turn of the 20th century was based on a very narrow version of skepticism instead of that you can't know anything about the universe. Just pointing that skepticism at certain things for which we have no evidence specifically mostly the God idea but also all sorts of things that we have no evidence for that we that people continue to believe in that this idea that you can't you can't prove a negative you can't know a negative but that's really not the case while while it's philosophically sound to say that we can't know anything. It is not philosophically sound to say that you can know some things but that certain types of things that you want to believe in but you don't have any evidence for those things you're gonna say you can't know anything about. If I have a plate of chicken in front of me I can't say I can't know whether or not it's steak I can know I know certain things they're evident in front of me and the things that we have evidence and proof for it or the things that after a long look at we have no evidence or proof that we can begin to say that we know one doesn't have to be agnostic about everything so while we are skeptics we're trying to elicit skepticism in other people but it's certainly possible for us to know that some things are not the case. I've got time for only a couple of examples but my books doubt the happiness myth and the end of the soul all are chock full of examples of people who had who were skeptics all through history it's remarkable how long it goes back the ancient Carvaca in India went were in 600 BC and they didn't believe that we could know anything and they were skeptical certainly of astrology of an after life one of the examples that I want to talk about today is Thomas Edison he was a known skeptic and doubter of all sorts of things and William James the very famous Harvard philosopher had been one of the people who was involved in scientific study of the after life. Sanctis were very big in this period and they were very big even in scientific circles. People had just found out about radioactivity and about the periodic table and there were a lot of things that were so new that people thought well maybe this very foreign subject is also going to be something that turns out to be true and World War one certainly had so many deaths in it that it encouraged a lot of people to want very much to have this communication with the dead and these things were mostly about Sanctis small groups of people meeting not the arena kind of talking to the dead that we have today but they were amazingly people by scientific minds Marie Curie and her husband went to them Shaul Rache who was a Nobel Prize winning scientist is the one who made up ectoplasm I'm sorry my slide for that isn't here but it's the goo that mediums would produce on themselves and on others in order to have a parent proof that something had happened and you can see this in Ghostbusters they get slimed this was the mediums were mostly from Italy and Spain and they came up into France and England and tricked a lot of people with a lot of flim flam so when William James was one of the believers in the scientific study of the afterlife he was not an outlier on this and he promised very publicly that when he died he would do his best to come back and contact somebody so a little while after he died one of his secretaries announced that she had been contacted by William James and and it made a huge splash a lot of newspapers covered it and New York Times covered it and they decided to dispatch a reporter to Thomas Edison a well known skeptic to see if they could find out what he thought of it and I'll I'll read you a little quote this is 1910 in New York Times which is pretty bold no this is Edison no all this talk of an existence for us as individuals beyond the grave is wrong it is born of our tenacity of life our desire to go on living our dread of coming to an end as individuals I do not dread it though personally I cannot see any use of a future life and a later communique he wrote I have never seen the slightest scientific proof of the religious theories of heaven and hell of future life individuals or of a proof or a personal God I work on certain lines that might be called perhaps mechanical proof proof that is what I have always been after he got in a lot of trouble a lot of a lot of letters but there were many other debunkers around the time same time but starting earlier in France there was a group called the Society of Mutual Autopsy I went to France to study them and down in the right under the Eiffel Tower there's the Chocodero the in the Museum of Mankind is there and down these long winding steps in the dark with a little flashlight I found these old metal cabinets and in them was the archives of the Society of Mutual Autopsy these were people who had met as atheists before they became they started the Society of Mutual Autopsy and they were well a silk plate would say they were dicks about it they were brashly offensive whenever they got the chance they they were brashly offensive in the process of campaigning the government to kick out the nuns from a municipal building which they actually succeeded in doing they changed street signs that were religious to from like Saint-etienne to Diderot Diderot being a famous enlightenment atheists are close to they fought against seances as well against a whole range of superstitious ideas what they meant by the Society of Mutual Autopsy was this they were they were inspired by Broca's aphasia I had a great slide about that too Broca's aphasia is on the third left frontal convolution of the brain if you have a lesion there you'll have trouble speaking so it was the first time anyone had ever proved a relationship between brain morphology and personality brain shape weight size and personality abilities and traits so the Society of Mutual Autopsy Broca was one of the people who joined the earliest and he was also one of the earliest brains dissected they waited till after death but a lot of these were older people who joined they were also inspired along with Broca they were inspired by the french translation of the origin of the species which came a little late and was done by a woman named Clémence Royer who had been a longtime atheist and a longtime believer in evolution lamarckian evolution and she wrote a preface to the origin of the species that was it was so thick it was a book of its own arguing that the origin of the pre-species proved atheism and the french got the origin of the species that way through her Darwin actually repudiated that translation about 10 years later but that was all they had for a long time so inspired by both these people they decided to start the Society of Mutual Autopsy and they advertised in it in all the left-wing leading journals and hundreds of people all over France and some around the world joined the Society of Mutual Autopsy and they sent in their their life stories because you had to be able to make a relationship between the abilities and the personality the original people who had founded it knew each other very well so they could dissect a brain and they made pronouncements they said this area was thick and after all this person had great spatial relations so maybe this has something to do with the truth is they didn't find anything anywhere near as concrete as Broca's aphasia in the 30 years that they practiced this they were also when they were doing this making a statement about their belief in in there being no afterlife and they they did that partially through making fun of seances but partially just by they had materialist deathbed scenes at the time in France they were published an awful lot of Catholic deathbed scenes where the person would announce that they were giving themselves up to God and they would reiterate their faith and so they had these materialist deathbed scenes where they would talk about proof and science and how in dying and giving their brains to dissection they were they were forwarding science and therefore living on the and Clemos Roye by the way the translator she she joined she was one of the one of them there were men and women from all over France who were part of the Society of Mutual Autopsy the reason they thought that this would prove to the Catholic Church that there was no soul was because at the time the definition of soul was really the thinking part of you the whole idea was that you that the the meat was just a the seat of the brain and the brain the mind was the soul and so nowadays that's just not what soul means anymore they just keep swerving to fit the evidence a little bit but that's what it meant at the time and so the idea was that to prove that there was a relationship there between what the brain looked like and what the brain could what the mind could do would be a way of proving this and in a way they won that is how it didn't get rid of the idea of the soul but it entirely changed what it was and made it much less powerful an explanation of what was going on with human beings the actions that they took part in had a poetic side to them there was poetry that they wrote also there were poets amongst them as well as many doctors and other kinds of scientists but also just the whole way they carried out their business in terms of ritualizing science a little bit and making well like those materialist death bed scenes making there be a kind of way of marveling at the universe as well as describing it so it's not just a matter of science but a matter of being aware of the wonders of science and I think in the term of the future of secularism we might do even more in our blogs and articles to not just have all with science but to have all with the things that are beyond science but still scientific by that I mean something like the sheer billions billions of galaxies out there were incredibly small and then of course the billions of human beings that are on the planet if you had billions of ping-pong balls on a table and one fell off it wouldn't matter but each of us matters tremendously it's a paradox it's something that thinking about makes us more human and I think some of the people who believe in strange things that are flimflam do so because they're hungry for something that reflects the inner life but there are things that are not flimflam that reflect the inner life that we can talk about and can think about another of the paradoxes is just the simple fact that we're all in our heads right now in our skulls looking out at each other I mean it's an amazing thing the meat thinks the meat wrote paradise lost the meat wrote all the symphonies the meat made the ipad it's it's shocking and it's something that you can never fully take in and it makes sense to run over it in your mind you know the church had some things right that you go back once a week these are things that you contemplate more and more and you get more and more out of them meditating on the wonders and paradoxes another way that we could take care of ourselves is something that I talk about in the happiness myth what I've been talking about so far a lot of it is in doubt but in the happiness myth I look at the way we for instance the way we eat the way we take drugs today the way we think about sex the way we think about a whole range of things including exercise the the notion that we have about exercise today is uh very skewed in history the only time in history that you can find people being as concentrated in the body beautiful as we are is the ancient spartans that had a but they had population of slaves larger than the members of the community um and the fascists the next one and there was also a plantation culture in in the south there had been tournaments that were also about the body beautiful we're in terrible company with this um not just health but but the the body beautiful to the point of the gym body and if you think about gyms how what a strange thing they are look if you looked if you were in some other culture and you looked at this or if this was in another if we looked at another culture that was so interested in the body beautiful we would say this was a martial culture this was a culture that was trying to promote a kind of strength and militarism um but also and it reiterates the idea of having an underclass we let someone else rake our leaves and we go to the gym we take the escalator to the stair master and there's a reason that we do it it's the underclass that goes home in dirty clothes we go home from work in dirty clothes and then switch to a gym bag that has that's where we sweat it's a way of saying to the culture who we are and so if you like gyms go to the gym and of course there are health benefits to a certain amount of exercise but the idea of cleaning one's own house taking walks when you had to go go places raking your own leaves the idea that the gym is a very peculiar place um it might be another kind of thing that along with the other things I talk about in the happiness myth another kind of broad range things that we could be skeptical about it's not just the flim flam but also just our own cultures biases and the things that we think are true um there's one more thing that I'll mention about ways that we could take care of ourselves um in terms of skepticism and that is um the new book I'm writing is called stay and it's about uh the history and the history of suicide and philosophy against it and it's very much a secular book um the religious people have their own answers for this god says don't do it um and of course a lot of religious people do it anyway thinking god will forgive um so even they need a secular argument against suicide and there it there have been throughout history uh philosophers who have come up with beautiful arguments that in one way we owe it to each other to stay alive that human beings copy each other we have a tremendous influence on each other and suicide clusters show us that the idea of staying alive for each other is a sort of strange one and it seems in some ways taxing to the person and I'm not talking about euthanasia at the end of life that seems like disease management that's a different thing but despair suicide we have a kind of live and let die attitude in the secular community about it and I think it's a wrong turn that we took because religion was so adamantly against it to the point of punishing corpses um and and taking away the estate of the suicide um so the secular community before the enlightenment but then very much with the enlightenment hum and uh the baron dolbach both wrote uh what you could actually say are almost pro-suicide tracks that were very much against the church but in no way looking at the situation in terms of humanism um but what I was saying was that while it seems almost cruel to say to a person who's in that much despair you have to stay the truth is as soon as you start to think about things that way the community becomes a warmer place you realize that staying alive even even sitting on your bed and crying or thinking about crying and you don't even have the energy to cry even that is a gift to the community if you want your niece to stay alive through the dark times you have to and it becomes the community becomes a richer place a place that you have more of a connection to and so I think the one thing that we're missing is gratitude and so I'll say it here thank you for staying thank you for staying alive to anybody out there who's ever thought about it that's one of the things I want the book to do to express gratitude and to recognize that it's a gift to the community and it's it's a tremendous contribution by someone who thinks that they can make no contributions because they're at the end of their at the end of their rope I think I'm gonna stop there and just say that these looking at history we can see a whole range from the ancient times to to to now I mean when I was writing doubt I thought I was just going to be seeing people who said no no no to religion and to superstition and instead I found people making suggestions about how we should live in that situation and that's what I think the future of skepticism needs to have we need to know our history and knowing our history will enrich who we are today and who we can be thank you Jennifer Michael Jennifer Michael


Michelangelo is never discovered from his genius. I mean, he is sometimes forced to do what he doesn't want to do, often forced to do what he doesn't want to do. And we can talk about that with Michelangelo. One of the great tragedies of history is what happens, in a sense, to Michelangelo. Because in my view, he's the greatest sculptor of all of history. And yet he doesn't sculpt much because he's forced to paint because that's what the pope wants him to do. But when he's identified as a great sculptor, people come to him. You know, here's the story about Michelangelo. Michelangelo is just this amazing kid. He's identified as a sculptor early on. He's brought into the Medici household, in a sense, he sculpts in this garden school outside of the Medici place. And he has admired for his sculpture. And at the age of 20, he goes to Rome. And he gets his first commission. And his first commission is the sculpt of Bacchus. Bacchus, Bacchus, something like that, the god of wine. And the god of wine is, of course, a Roman god, a Greek god. And often, the god of wine in sculpture before Michelangelo is always portrayed as the strong raising a glass of wine, kind of very powerful, positive, almost heroic character. And Michelangelo, and it'd be interesting to go into the reasons. I would be interested in going into the reasons for this. But Michelangelo, instead, portrays the god of wine, who is just, this is Dionysus, of course, in Greek. Thank you, Jennifer, who is a little tipsy. He's a little drunk. He's got a beautiful body, but it's a body that's standing in kind of a relaxed pose. And his eyes, you can see, are a little out of focus. And it's a look of genius. I mean, you can see it in Florence at the Bodello Gallery. It's an amazing sculpture. But he is clearly drunk. He's the god of wine. He's what you think of with the god of wine. And I wouldn't be surprised if Michelangelo here is doing a sculpture that's trying to critique the person who actually commissioned the sculpture in a sense of, you Christians who love wine, this is what you look like. It's a nude. It's an amazing sculpture if you go and see it, right? It's not heroic. It doesn't necessarily appeal to me thematically. But when you look at what he's done and how he conveys what he's trying to convey, it's a magnificent piece of work. Anyway, when he shows this, the guy who does the commission says, go away. I mean, I'm not going to pay you for this.  This is not what I expected. I expected a heroic, celebratory, toasty god of wine. You can see in the bordello, there are other gods of wine exactly the same with that more heroic, more positive theme. So you can see the contrast of what the guy wanted as part of the commission. Well, Michelangelo is stuck with this. Ultimately, the Medici's buy this and they ship it back to Florence because it's such a great work of art and they realize that. But Michelangelo is in trouble now and he needs another commission desperately. And there is a competition to do a pietà.  And Michelangelo sculpts in marble a pietà. And if you've never seen the pietà by Michelangelo, the first one he does, he does at least three. But the other two are not never finished. But this one is finished. You've got to go, it's in the Vatican Museum. It's in the Vatican in Rome. Unfortunately, you can't get very close to it. It's behind glass because somebody at some point took a shot at it with a gun. So they put it behind glass. It is just one of the most stunning pieces of art ever.  The son is strong, heroic to the extent you can tell from the dead body. And she is mourning. And you can tell from her expression. You can tell from the way her hands hold him. You can tell just from the way the clothes are draped over her. It's just a stunningly amazing, unbelievably beautiful sculpture that evokes all the emotion that I think a pietà should evoke. Now, I want to make a point here. Sideline. So we're going in all kinds of directions today. But hopefully this is a value, too. Why can one look at a pietà and a Jesus on a cross and have a positive aesthetic experience? It's Jesus.  I said it.  I've said it many times. And yet here's the symbol of Christianity. And yet when you look at a pietà, or you look at some of the magnificent paintings during the Renaissance and later of a crucifixion, or if you look at Dali's crucifixion, which I in fact really liked. What is it about a crucifixion that is so powerful? And how can one abstract? How can one enjoy it, in a sense, or get something out of it? And I think to me is I abstract away from the Christian part of it. And I think of Jesus as a fighter for a new set of ideas. As somebody who believes in a new set of ideas and is fighting to have the manifest in the world, somebody heroic who is going around advocating for new ideas and who is put to death because of his ideas. Jesus did not commit a crime.  He did not steal from anybody. He was a man punished for speaking. In a sense, the crucifixion, I'm putting aside all the Christian meaning, which it means to Christians. I'm putting what it means to me, is a sign, a symbol of the injustice of injustice, of what happens to heroes so many times throughout history. Yeah, by the way, yeah, so many times throughout history that where people who advocate for new ideas, people who advocate for radical ideas get crucified, get crucified. And in art that is actually presents Jesus as heroic, that is manifest physically heroic, right? Intelligent face, intelligent expression, heroic body, muscles alive, not a symbol of sacrifice, but a representation of an injustice committed to a heroic figure, to a heroic man. To that extent, I can enjoy a crucifixion. In a sense that it projects back to me, it concretizes the injustice that often occurs and you can benefit from. You can get from portrayals of injustice a huge amount. It is real. And this is why I can enjoy like Dark Ages or Middle Ages, crucifixions, but when you get into the Renaissance, particularly into the high Renaissance, the later Renaissance, Michelangelo's period, it's amazing. And then when you look at the pietà, this pietà of Michelangelo's, I mean, he is a hero. He is the mother of a hero. And the tragedy of it, the sadness of it, and yet the beauty of it are so striking. Now, the pietà was universally immediately identified as a great work of art. But people said, who did it? And somebody said, Michelangelo. They said, no, that can't be.  It can't be Michelangelo. Michelangelo is a nobody and he can't sculpt like this. There's no way he could do this. So there was a general rumor going around that it wasn't Michelangelo who sculpted the painting. So one night, who sculpted the pietà. So one night, Michelangelo snuck into the place where the sculpture was stored and he chiseled into the strap that goes across Mary's body. Michelangelo did this or something to the equivalent of that. Michelangelo sculpted this. Only sculpture he ever signed. After that, he didn't need to sign any sculpture because everybody knew of Michelangelo when they saw it. Of course his reputation, the pietà, made Michelangelo's reputation. He was immediately elevated to being the number one sculptor of the Renaissance. Sculptor of his generation and maybe, and I believe ultimately of all time.  I don't know, I can't remember the exact timing but it's not like 80 years. It's been there a long time. And two sculptors have tried to sculpt into this. They've already chiseled into this. So they've chiseled into the top and they've chiseled into the bottom. And as they've already tried to sculpt it and both sculptors, this is a massive piece of marble, they both walked away saying, this is impossible. It is impossible to use this piece of marble. It's not a good piece of marble, it's too big but there are flaws in it, there are problems with it, we can't do it. And this piece of marble is just sitting there. It's owned by the city of Florence. And Michelangelo goes and he goes to the leaders of Florence and he says, I wanna do this. And they say, no, nobody can do it. It's just, we need to trash this piece of marble. Nobody can sculpt it. It's useless and they've already started. So you couldn't do anything anyway. He says, no, I wanna do this. And he bugs them and he bugs them and he bugs them and he's got this reputation. And he's a young kid, he's 25 years old by this point and the Medici's, he found kind of originally found them, the Medici's like him. So then they say, okay, do it, take it and do it. And here's this piece of marble that everybody thought was, you couldn't carve anything from it. And carvings that are already being done. Now marble is not like bronze. Bronze you sculpt in clay.  Marble, once you chisel something away, it's gone. You don't stick it back. It's gone forever. So some of the pieces already being chiseled away. And Michelangelo sets this up in a studio and he works on it. And out of that piece of marble comes, in my view, the greatest sculpture that's ever been produced, the David.   And when you understand marble and you see the flaws in the marble, the marble was flawed. And the fact that Michelangelo can work in spite of the flaws in the marble can create this magnificent piece of work in his mid-20s is truly, truly stunning. Now here's a David who is again naked. He's nude. He stands with confidence in Father Goliath with a look of concentration, focus on what he has to do. It is the moment before he strikes, before the fight begins. Most Davids are either of the moment afterwards with the head of Goliath already there, the moment of victory, Donatello's Goliath, Volcaccio's Goliath, all at the moment of victory. Later, Bernini will sculpt a magnificent David which is at the moment of action. You can see David in action using his, what do you call it, anyway. Getting that stone using this sling. Yeah, Jennifer, that is a picture that's kind of a drawing of Michelangelo's David in the background over there. It's really, it's really special. The primary purpose of art is contemplation for its own sake. So that the purpose here is for the reader to see what greatness man is capable of and to be inspired by that. So as I read Atlas Shrugged and any one of the heroic characters, Hank Reardon or John Gault or Francisco, these give me a model of the kind of person I might be. If you wish, but that isn't my purpose in writing. I see. My purpose is for you to look at those people and to enjoy the spectacle. As a secondary consequence, you might find yourself inspired, that's fine. But I want to give you that experience and that's what I want to give myself. I write for the purpose of creating an ideal man in actions which you can respect and admire. From what you say about art, I would judge you do not regard photography as art since it records precisely what is there. How do you feel about abstract art? Do you mean non-objective? Non-objective. I think it's less art than photography. I think it is an enormous fraud. Fraud? Yes. I don't think there's, it's impossible to discuss it seriously. It means nothing, it is nothing. The perpetrators claim that they don't know what they're doing and I think they're right. I'm willing to take them at their word. They don't know what they're doing and neither do we and the Ashken is the proper place for it.