"Up until now, everyone would take separate pieces of the material, measure each piece, and compare differences to quantify non-uniformity," Grayson said. "That means you need more time to make several different measurements and extra material dedicated for diagnostics. We have figured out how to measure a single piece of material in a magnetic field while flipping the polarity to deduce the average variation in the density of electrons across the sample."
One reason semiconductors have so many applications is because researchers and manufacturers can control their properties. By adding impurities to the material, researchers can modulate the semiconductor's electrical properties. The trick is making sure that the material is uniformly modulated so that every part of the material performs equally well. Grayson's technique is said to allow researchers and manufacturers to directly quantify such non-uniformities.
"When people see non-uniform behaviour, sometimes they just throw out the material to find a better piece," Grayson said. "With our information, you can find a piece of the material that's more uniform and can still be used. Or you can use the information to figure out how to balance out the next sample."
Grayson says his method can be applied to samples as large as a 12-inch wafer or as small as an exfoliated 10µm flake, allowing researchers to profile the subtleties in a range of semiconductor samples. The method is claimed to be especially useful for 2D materials, such as graphene, which are too small for researchers to make several measurements across the surface.
Grayson has filed a patent on the method, and hopes the technique will find use in academic laboratories and industry.
