Investigation of Photoelectric Effect in Transition Metal Dichalcogenides Field Effect Transistors

Author(s): Lu, I-Hsi Daniel | Advisor(s): Bartels, Ludwig | Abstract: Investigation of photoelectric effect in Transition Metal Dichalcogenides Field Effect TransistorsBy: I-Hsi Daniel LuAbstract:One atomically thin two-dimensional materials like graphene was brought into the spotlight as an ideal high mobility material for electronics once it was synthesized by Dr. Andre Geim and Dr. Kostya Novoselov. The two professors found an ingenious way to extract graphene from graphite through a method later known as exfoliation. This opened a gateway for people to learn more about 2-D materials. However, graphene lacks a direct bandgap due to its single carbon sheet structure. Thus, transition metal dichalcogenide (TMDs) has been studied for its direct bandgap and decent mobility properties. Two-dimensional materials have then been synthesized through different methods such as exfoliation and chemical vapor deposition (CVD). TMDs are materials with the form of MX2 (M= Transition metal; X= Chalcogen). Each different combinations of such materials can provide different properties. Due to its unique crystal structure, it forms a direct bandgap in between the transition metal and chalcogen in single layer form. This property allows for functions of optoelectronic devices. In my work, I demonstrate photocurrent emission of monolayer MoS2 films using a home-built scanning photocurrent microscope. The purpose of the work is to investigate the Schottky barrier difference among different metal composition.