text: Ernst Bauer first described a “low energy” variety of these devices that can analyze thin films.
full_question: Ernst Bauer first described a “low energy” variety of these devices that can analyze thin films. The resolution of these devices can be improved by using a lanthanum hexaboride cathode instead of a tungsten cathode. Before use with one type of these devices, samples are often either stained with osmium or coated in a layer of gold. Surface morphology can be determined using the “scanning” variety of these devices, while their “transmission” variety requires the use of an ultrathin sample. For 10 points, name these magnification devices that use negatively charged particles.
first_sentence: Ernst Bauer first described a “low energy” variety of these devices that can analyze thin films.