Superconducting Diamond on Silicon Nitride for Device Applications

TL;DR

This study investigates how different surface treatments of silicon nitride influence the growth quality and superconducting properties of diamond films, aiming to optimize diamond-based device fabrication.

Contribution

It demonstrates that oxygen plasma treatment of silicon nitride enhances diamond seeding and growth, resulting in improved superconducting transition properties.

Findings

Oxygen plasma treatment yields optimal surface conditions for diamond seeding.

Diamond films grown on oxygen plasma treated substrates show the sharpest superconducting transition.

RCA-1 treatment leads to pin-holing in diamond films.

Abstract

Chemical vapour deposition (CVD) grown nanocrystalline diamond is an attractive material for the fabrication of devices. For some device architectures, optimisation of its growth on silicon nitride is essential. Here, the effects of three pre-growth surface treatments, often employed as cleaning methods of silicon nitride, were investigated. Such treatments provide control over the surface charge of the substrate through modification of the surface functionality, allowing for the optimisation of electrostatic diamond seeding densities. Zeta potential measurements and X-ray photoelectron spectroscopy (XPS) were used to analyse the silicon nitride surface following each treatment. Exposing silicon nitride to an oxygen plasma offered optimal surface conditions for the electrostatic self-assembly of a hydrogen-terminated diamond nanoparticle monolayer. The subsequent growth of boron-doped nanocrystalline diamond thin films on modified silicon nitride substrates under CVD conditions produced coalesced films for oxygen plasma and solvent treatments, whilst pin-holing of the diamond film was observed following RCA-1 treatment. The sharpest superconducting transition was observed for diamond grown on oxygen plasma treated silicon nitride, demonstrating it to be of the least structural disorder. Modifications to the substrate surface optimise the seeding and growth processes for the fabrication of diamond on silicon nitride devices.