Crystalline Formations of NbN/4H-SiC Heterostructure Interfaces

TL;DR

This study investigates the temperature-dependent interfacial interactions of NbN films on 4H-SiC substrates, revealing diffusion, nanocrystallite formation, porosity, and voids through microscopy and spectroscopy analyses.

Contribution

It provides new insights into the effects of high-temperature treatments on NbN/SiC interfaces, highlighting diffusion and structural changes relevant for device fabrication.

Findings

NbN diffuses into SiC at 1400°C

Nanocrystallites form within SiC during heat treatment

High-temperature treatment causes porosity and void formation

Abstract

Given the importance of incorporating various superconducting materials to device fabrication or substrate development, studying the interface for possible interactions is warranted. In this work, NbN films sputter-deposited on 4H-SiC were heat-treated at 1400 C and 1870 C and were examined with transmission electron microscopy to assess whether the interfacial interactions undergo temperature-dependent behavior. We report the diffusion of NbN into the SiC substrate and the formation of NbN nanocrystallites therein during the 1400 C treatment. After the 1870 C treatment, tiered porosity and the formation of voids are observed, likely due to catalytic reactions between the two materials and accelerated by the stresses induced by the differences in the materials' coefficients of thermal expansion. Lastly, Raman spectroscopy is employed to gain an understanding of the interface lattices' optical responses.