Adhesion of the electrodes on diamond device surfaces

TL;DR

This study uses density functional theory to evaluate the adhesion and electronic contact quality of various metals on diamond surfaces, identifying transition metals with stronger adhesion than gold for electrode applications.

Contribution

It provides a computational assessment of metal-diamond interfaces, highlighting transition metals with improved adhesion and Ohmic contact properties over traditional gold electrodes.

Findings

Gold has insufficient adhesion for power device electrodes.

Transition metals like Cr and Ti show stronger adhesion and suitable electronic contact.

DFT simulations effectively predict interface properties for material selection.

Abstract

Appropriate candidates of the metallic sheet used for the electrodes of diamond semiconductor are investigated using computational approaches based on density functional theory (DFT). For twenty kinds of metallic elements $x$, we modeled a diamond-metal interface and evaluated its work of separation, $W_\mathrm{sep}(x)$, as a possible measure of anti-peeling strength. The appropriateness of the Ohmic contact was inferred from DOS (density of states) analysis of diamond-metal interface by looking at whether an in-gap (isolated/localized) peak disappears as well as a sufficient amount of DOS value exists around the Fermi level. Our DFT simulation confirmed that a typical electrode, Au, is not adhesive enough for power devices [$W_\mathrm{sep}(\mathrm{Au}) = 0.80$ J/m$^2$], though showing the Ohmic contact. In contrast, some transition metals were found to possess Ohmic features with much stronger adhesion than Au [e.g., $W_\mathrm{sep}(\mathrm{Cr}/\mathrm{Ti}) = 6.02/4.03$ J/m$^2$].