Structure and composition of interfaces between 2D materials and dielectric substrates

The rich and exciting electronic and mechanical properties of two-dimensional (2D) materials have inspired novel ideas for post-silicon nanoelectronics. Some of the most far-reaching of them concern the possible substitution of Si with 2D materials in modern field-effect transistors (FETs) and applications in next-generation memory and neuromorphic computing chips. Success of these applications relies on solving the materials problems related to defects at interfaces between 2D materials and gate dielectrics or metal electrodes. For example, the sandwich structure of memristive devices is usually composed of an insulating active layer (e.g., transition metal oxides (TMOs)), 2D material (graphene, MoS2) and top/bottom metal electrodes. This project will combine theoretical modelling of such interfaces with experimental investigations of their properties using hard x-ray photoelectron spectroscopy (HAXPES). Theoretical simulations of interfaces of 2D materials, such as MoS2 and WSe2, with SiO2, HfO2 and CaF2 insulating layers will be used to analyse the experimental HAXPES spectra of these systems and study the properties of point defects at interfaces. HAXPES measurements at DIAMOND and other facilities will help us to elucidate the effects of deposition and adsorbates on the chemical composition of interfaces. Theoretical calculations using both atomistic simulations and density functional theory calculations should allow us to identify interface defects as well as oxide defects near interfaces and relate them to reliability issues pertaining to FETs and mechanisms of resistive switching of oxides.