Public Release:  Technique turns computer chip defects into an advantage

Ohio State University

COLUMBUS, OHIO - Physicists at Ohio State University have discovered that tiny defects inside a computer chip can be used to tune the properties of key atoms in the chip.

The technique, which they describe in the journal Science, involves rearranging the holes left by missing atoms to tune the properties of dopants - the chemical impurities that give the semiconductors in computer chips their special properties.


"The effect we discovered is probably already going on inside the devices we use every day - it's just not being controlled," said Jay Gupta, assistant professor of physics at Ohio State and principal investigator on the project. "Once industry takes this effect into account, our discovery could not only enable future computers with faster speeds, but could also enable new paradigms for computing - based, for example, on quantum mechanics."


Researchers commonly nudge atoms with an STM's electric field to rearrange them. In the case of these chip materials, the rearrangement process was like playing a sliding tile puzzle, Gupta explained; they rearranged the vacancies - empty holes, considered defects - in the material.

For example, they found that an arsenic vacancy on the surface of the material - like the missing tile in a puzzle - could be effectively moved by nudging an arsenic atom into a different nearby hole, thus resulting in a new hole where the arsenic atom used to be.

The hole left by the arsenic atom has its own electric field, and the researchers studied the influence of this field on nearby dopants - in this case, manganese atoms. They noticed that the dopant's energy level dropped when the hole was moved nearby, and increased when it was moved away.

Dopants are important in semiconductor devices such as computer chips because they enable very sensitive control over the current flow, depending on temperature and applied voltage. The dopant's energy is the key parameter that determines this ability.



While chip makers aren't likely to employ STMs in their production lines anytime soon, Gupta believes that they could take advantage of the discovery in a practical way - by manipulating tiny electric fields across the metal electrodes that already exist on top of chips.


Today, a single chip may contain only a few dozen dopant atoms that are critical to its performance. As chips get smaller, the performance of every atom will count even more, and techniques such as Gupta's that can control individual dopant atoms could become very important.




