Atomic Scale Study of Thermal Properties using STEM/EELS and First-principles Calculations

As predicted by Moore’s Law, the density of transistors has doubled every two years which was contributed significantly to the miniaturization of electronic devices. When the dimensions of a transistor approach the single-atom limit, as in devices consisting of two-dimensional materials, including graphene, transition metal dichalcogenides (TMDs) and their heterostructures, such miniaturization offers remarkable improvements in electrical performance. However, heat dissipation and thermal expansion mismatch can cause problems in designing electronic devices based on two-dimensional materials. Therefore, the nanoscale thermal properties are an important subject of current research in two-dimensional materials, and, correspondingly, new methods are needed for temperature measurements and thermal property measurements at nanometer scale. In my thesis, I have developed a novel method for measuring local temperature and the thermal expansion coefficient of two-dimensional materials, using a combination of scanning transmission electron microscope (STEM), electron energy loss spectroscopy (EELS) and first-principles calculations.