Electronic Stopping of Slow Protons in Oxides: Scaling Properties

TL;DR

This study investigates how slow protons lose energy in various oxides, revealing that oxygen density, not electronic properties like band gap, primarily determines stopping behavior at low velocities.

Contribution

It demonstrates that electronic stopping cross sections in oxides scale with oxygen density, supported by experimental data and density functional theory calculations.

Findings

Stopping cross sections do not correlate with band gap energies.

Oxygen 2p states are key in electronic stopping.

SCS scales with oxygen density in oxides.

Abstract

Electronic stopping of slow protons in ZnO, VO2 (metal and semiconductor phases), HfO2, and Ta2O5 was investigated experimentally. As a comparison of the resulting stopping cross sections (SCS) to data for Al2O3 and SiO2 reveals, electronic stopping of slow protons does not correlate with electronic properties of the specific material such as band gap energies. Instead, the oxygen 2p states are decisive, as corroborated by density functional theory calculations of the electronic densities of states. Hence, at low ion velocities the SCS of an oxide primarily scales with its oxygen density.