Potential barrier heights at metal on oxygen-terminated diamond interfaces

TL;DR

This study investigates the electrical properties and barrier heights at metal on oxygen-terminated diamond interfaces, revealing how annealing and interface dipoles influence Schottky barrier behavior and challenge conventional models.

Contribution

It introduces a generalized model for barrier height inhomogeneities at diamond interfaces, accounting for chemical evolution and interface dipoles, and compares experimental data with theoretical predictions.

Findings

Barrier heights vary from 2.2-2.5 V unannealed to 0.96 V after annealing at 450°C.

Interface dipoles and chemical evolution explain the reversed slope trend.

The model aligns with experimental data, enhancing understanding of diamond-metal interfaces.

Abstract

Electrical properties of metal-semiconductor (M/SC) and metal/oxide/SC structures built with Zr or ZrO\_2 deposited on oxygen-terminated surfaces of (001)-oriented diamond films, comprising a stack of lightly p-doped diamond on a heavily doped layer itself homoepitaxially grown on a Ib substrate, are investigated experimentally and compared to different models. In Schottky barrier diodes, the interfacial oxide layer evidenced by high resolution transmission electron microscopy and electron energy losses spectroscopy before and after annealing, and barrier height inhomogeneities accounts for the measured electrical characteristics until flat bands are reached, in accordance with a model which generalizes that of R.T. Tung [Phys. Rev. B 45, 13509 (1992)] and permits to extract physically meaningful parameters of the three kinds of interface: (a) unannealed ones; (b) annealed at 350{\textdegree}C; (c) annealed at 450{\textdegree}C, with characteristic barrier heights of 2.2-2.5 V in case (a) while as low as 0.96 V in case (c). Possible models of potential barriers for several metals deposited on well defined oxygen-terminated diamond surfaces are discussed and compared to experimental data. It is concluded that interface dipoles of several kinds present at these compound interfaces and their chemical evolution due to annealing are the suitable ingredients able to account for the Mott-Schottky behavior when the effect of the metal work function is ignored, and to justify the reverted slope observed regarding metal work function, in contrast to the trend always reported for all other metal-semiconductor interfaces.