Ion-beam Assisted Sputtering of Titanium Nitride Thin Films

TL;DR

This study compares conventional reactive sputtering and ion-beam assisted sputtering (IBAS) for titanium nitride thin films, showing IBAS improves critical temperature and reduces nitrogen sensitivity, with implications for superconducting device fabrication.

Contribution

It demonstrates that IBAS enhances TiN film properties by increasing Tc and reducing nitrogen sensitivity without altering lattice structure, compared to conventional sputtering.

Findings

IBAS increases critical temperature by 10%.

IBAS reduces nitrogen flow sensitivity by 33%.

Superconducting Tc trends align with mean-field theory at high nitrogen concentrations.

Abstract

Titanium nitride is a material of interest for many superconducting devices such as nanowire microwave resonators and photon detectors. Thus, controlling the growth of TiN thin films with desirable properties is of high importance. In previous work on niobium nitride, ion beam-assisted sputtering (IBAS) reduced nitrogen sensitivity during deposition in tandem with an increase in nominal critical temperature. We have deposited thin films of titanium nitride by both, the conventional method of DC reactive magnetron sputtering and the IBAS method and compare their superconducting critical temperatures Tc as functions of thickness, sheet resistance, and nitrogen flow rate. We perform electrical and structural characterizations by electric transport and X-ray diffraction measurements. Compared to the conventional method of reactive sputtering, the IBAS technique has demonstrated a 10% increase in nominal critical temperature and 33% reduced sensitivity to nitrogen flow, without noticeable variation in the lattice structure. Additionally, we explore the behavior of superconducting Tc in ultra-thin films. Trends in films grown at high nitrogen concentrations follow predictions of mean-field theory in disordered films and show suppression of superconducting Tc due to geometric effects, while nitride films grown at low nitrogen concentrations strongly deviate from the theoretical models.