Synthesis of nanocrystalline d-MoN by thermal annealing of amorphous thin films grown on (100) Si by reactive DC sputtering at room temperature

TL;DR

This study demonstrates a method to synthesize nanocrystalline delta-MoN superconducting thin films on silicon via reactive sputtering and thermal annealing, with critical temperatures approaching bulk values.

Contribution

It introduces a simple annealing process to convert amorphous MoN films into superconducting delta-MoN nanocrystals on silicon substrates.

Findings

Nanocrystalline delta-MoN forms after annealing above 600°C.

Thicker films exhibit higher Tc, up to 11.2 K.

Superconducting Tc is dependent on film thickness.

Abstract

We report on the synthesis and characterization of nanocrystalline delta-MoN by crystallization of amorphous thin films grown on (100) Si by reactive sputtering at room temperature. Films with chemical composition MoN were grown using a deposition pressure of 5mTorr with a reactive mixture of Ar/(Ar+N2)=0.5. The as-grown films display mostly amorphous structure. Nanocrystalline delta-MoN phase is obtained after annealing at temperatures above 600 {\deg}C. The superconducting critical temperature Tc depends on film thickness. Thick films (170 nm) annealed at 700 {\deg}C for 30 min display a Tc = 11.2 K (close to the one reported for bulk specimens: 13 K), which is gradually suppressed to 7.2 K for 40 nm thick delta-MoN films. Our results provide a simple method to synthesize superconducting nitride thin films on silicon wafers with Tc above the ones observed for conventional superconductors such as Nb.