Metal Termination Effects on the Structural and Electronic Properties of Diamond (100) Surfaces: A Study of Ti, Zr, Hf, Mo, and Al

Diamond is a promising semiconductor with exceptional structural, thermal, and electronic properties. When metals are combined with diamond, they can induce electronic properties such as negative electron affinity, thermal stability, and low contact resistance. This is critical for the advancement of diamond-based devices; however, no metal has yet been identified as a robust low-resistance contact. Part of the issue is the uncertainty regarding the morphology of an interfacial layer between the diamond and the metal. The goal of this study is to model the structure of a potential interface layer and understand how it influences the Schottky Barrier Height (SBH) between diamond and metals, specifically Al, Ti, Hf, Zr, and Mo. We will present the results of density functional theory calculations (DFT), examining electronic properties of monolayer films of metal-carbides on diamond. The parameters included the Perdew-Burke-Enzernhof exchange-correlation functional, an 8x8x1 monkhorst-pack kpoint mesh, and a plane wave cut off of 500 eV to relax these surfaces. The metal and carbon were added to the diamond surface one at a time by scanning them across the surface. In our study, we observed a mixing in between the metal and carbon in the atom-by-atom deposition. For the investigated surfaces--TiC, ZrC, HfC, and MoC--the dipole moment was found to have a negative correlation with the SBH, except Al3C4. Finally, an approach for controlling the SBH using these materials at the surface will be proposed.