Synthesis and study of ScN thin films

TL;DR

This study demonstrates room-temperature sputtering for high-quality ScN thin films, analyzing their structural, optical, and mechanical properties, and introduces novel spectroscopic validation methods for the Sc-N system.

Contribution

It presents a new room-temperature synthesis route for ScN thin films and employs innovative spectroscopic techniques for detailed phase and composition analysis.

Findings

Successful room-temperature deposition of textured ScN films.

Optical bandgap varies between 2.25-2.62 eV.

Hardness and modulus increase linearly with resistance to deformation.

Abstract

To contemplate an alternative approach for the minimization of diffusion at high temperature depositions, present findings impart viability of room-temperature deposited reactively sputtered ScN thin film samples. The adopted room temperature route endows precise control over the $R_{N_2}$ flow for a methodical structural phase evolution from Sc$\to$ScN and probe the correlated physical aspects of the highly textured ScN samples. In the nitrided regime i.e. at $R_{N_2}$ = 2.5-100% flow, incorporation of unintentional oxygen defects were evidenced from surface sensitive soft x-ray absorption spectroscopy study, though less compared to their metal ($R_{N_2} = 0\%$) and interstitial ($R_{N_2} = 1.6\%$) counterparts, due to higher Gibb's free energy for Sc-O-N formation with no trace of ligand field splitting around the O K-edge spectra. To eradicate the sceptism of appearance of N K-edge (401.6 eV) and Sc L-edge (402.2 eV) absorption spectra adjacent to each other, the nascent Sc K-edge study has been adopted for the first time to validate complementary insight on the metrical parameters of the Sc-N system taken into consideration. Optical bandgaps of the polycrystalline ScN thin film samples were found to vary between 2.25-2.62 eV as obtained from the UV-Vis spectroscopy, whereas, the nano-indentation hardness and modulus of the as-deposited samples lie between 15-34GPa and 152-476GPa, respectively following a linearly increasing trend of resistance to plastic deformations. Besides, contrary to other early 3d transition metal nitrides (TiN, VN, CrN), a comprehensive comparison of noticeably large homogeneity range in Sc-N has been outlined to apprehend the minuscule lattice expansion over the large $R_{N_2}$ realm.