UC Riverside

ABSTRACT OF THE DISSERTATION

Schottky Barrier Heights at Two-Dimensional Metallic and Semiconducting

Transition-Metal Dichalcogenide Interfaces

by

Adiba Zahin

Master, Graduate Program in Electrical and Computer Engineering

University of California, Riverside, September 2017

Dr. Roger K. Lake, Chairperson

Several advances have been made in the realization of electronic devices that utilize

atomically thin two-dimensional (2D) materials. The semiconducting transition metal

dichalcogenides in particular have been used to demonstrate a wide range of devices

which include steep tunnel-field-effect transistors [1,2], photodetectors [3,4], field-effecttransistors [5, 6] and chemical sensors [7, 8]. A variety of experimental [9, 10] and theoretical [11, 12] studies have been devoted to understand the interface formed between

the bulk metals that are deposited on the surface of the 2D transition metal dichalcognides. There is growing evidence that the Schottky-like transport behavior observed

in TMDC-metal contacts is a consequence of strong Fermi level pinning (FLP). The

origin of the Fermi level pinning in metal-TMDC interfaces has been attributed to the

formation of interface dipoles [11], defects at the metal-TMDC interface and the existence of metal-induced-gap-states (MIGS) which arise from the exponential decay of

the wavefunction of the metal Fermi level into the TMDC band gap [13, 14]. One approach to minimize the effect of Fermi level pinning would be achieving an epitaxially

clean interface between the metal and the semiconducting TMDC. Prior experimental

studies of the contact resistance between the 2H/1T polytypes of MoS2 succeeded in

idemonstrating record low contact resistance [15]. Indeed recent study shows that, FLP