# Thick adherent diamond films on AlN with low thermal barrier resistance

## TL;DR

This study demonstrates the successful growth of thick, adherent diamond films on plasma-treated AlN substrates, achieving significantly improved thermal barrier resistance, with detailed surface and interface characterization confirming the quality of the films.

## Contribution

It introduces a plasma treatment method that enables the growth of thick diamond films on AlN with low thermal barrier resistance, advancing thermal management materials.

## Key findings

- Thick diamond films (>100 μm) adhere on plasma-treated AlN but not on untreated.
- Surface treatments alter surface chemistry and zeta potential, improving adhesion.
- Thermal barrier resistance achieved is approximately 16 m²K/GW, a notable improvement.

## Abstract

Growth of $>$100 $\mu$m thick diamond layer adherent on aluminium nitride is presented in this work. While thick films failed to adhere on untreated AlN films, hydrogen/nitrogen plasma treated AlN films retained the thick diamond layers. Clear differences in zeta potential measurement confirms the surface modification due to hydrogen/nitrogen plasma treatment. Areal Raman maps showed an increase in non-diamond carbon in the initial layers of diamond grown on pre-treated AlN. The presence of non-diamond carbon has minimal effect on the interface between diamond and AlN. The surfaces studied with x-ray photoelectron spectroscopy (XPS) revealed a clear distinction between pre-treated and untreated samples. The surface aluminium goes from nitrogen rich environment to an oxygen rich environment after pre-treatment. Cross section transmission electron microscopy shows a clean interface between diamond and AlN. Thermal barrier resistance between diamond and AlN was found to be in the range of 16 m$^2$K/GW which is a large improvement on the current state-of-the-art.