Schottky Barrier Heights of Defect-free Metal/ZnO, CdO, MgO and SrO Interfaces

TL;DR

This study uses density functional calculations to analyze Schottky barrier heights at defect-free metal/oxide interfaces, revealing how barrier heights depend on oxide ionicity, interface polarity, and metal work function.

Contribution

It provides a systematic computational analysis of SBHs for various metal/oxide interfaces, including effects of interface polarity and oxide ionicity, with corrections for band gap errors.

Findings

SBHs decrease linearly with increasing metal work function.

Pinning factors vary with oxide ionicity, from 0.26 to 0.96.

Interfacial dipoles cause significant SBH shifts at polar interfaces.

Abstract

The Schottky barrier heights (SBHs) of defect-free interfaces of ZnO, CdO, MgO and SrO with various metals and different terminations are investigated by density functional supercell calculations. The oxide bands are corrected for their density functional band gap error by applying U-type treatment to their metal-d and O-p states where necessary. The p-type SBHs are found to decrease linearly with increasing metal work function. The pinning factor S of the non-polar and polar interfaces are similar for each oxide. S is found to be 0.26, 0.56, 0.74 and 0.96 for CdO, ZnO, MgO and SrO, respectively, with S increasing for increased oxide ionicity. The calculated pinning factors are generally consistent with the metal-induced gap states (MIGS) model in terms of variation with ionicity and dielectric constant. A significant shift of SBHs from the non-polar to the polar interfaces of 0.4 eV, 1 eV and 0.5 eV for ZnO, MgO and SrO, respectively, can be explained by an interfacial dipole. Our results are also useful to describe Co,Fe|MgO interfaces in magnetic tunnel junctions.