Comprehensive nanoscopic analysis of tungsten carbide/Oxygenated-diamond contacts for Schottky barrier diodes

Abstract

Tungsten carbide (WC) contacts deposited on oxygenated diamond surface have shown great importance in the field of diamond-based Schottky diodes. In previous works, high temperature stability up to 600 K, an ideality factor close to 1 with a Schottky Barrier Height (SBH) of ~1.5 eV have been demonstrated by electrical measurements. Annealing at higher temperature lead to the deterioration of the contact behaviour in terms of SBH and ideality factor. The reaction between deposited material and diamond or the desorption of oxygen at the interface has been tentatively linked to this phenomenon. In this work, the composition of the WC/O-diamond interfaces annealed at 600 K are analysed by X-ray photoelectron spectroscopy (XPS) depth profile with low energy Ar+ ion sputtering for the first time. The microstructure of the contact is analysed by high-resolution transmission electron microscopy (HR-TEM). The formation of a metastable cubic-WC phase at the interface and the presence of interface oxygen is evidenced. The SBH of the WC/O-diamond contact is estimated by XPS at 1.6 ± 0.2 eV in agreement with I/V measurements.