Growth, surface morphology, optical properties and electrical resistivity of ε-TiN_x (0.4<x≤=0.5) films

Abstract

The growth, structure, surface morphology, optical properties and electrical resistivity studies on TiN_x (0.4<x≤0.5) films is presented. The films of thickness 116–230 nm were grown on fused silica substrates by RF magnetron sputtering in 100% pure nitrogen atmosphere at ambient temperature and pressures from 12 to 25 mTorr. For the as-deposited films, the refractive index decreased from 1.86 to 1.6 with increasing N₂ pressure from 12 to 25 mTorr. The absorption edge for the film deposited at 12 mTorr was 4.7 eV and it decreased to 3.5 eV on increasing the N₂ pressure to 25 mTorr. Post-deposition annealing of the films at 873 K for 1 min did not cause any variation in the optical properties. The film deposited at 25 mTorr and annealed at 873 K showed a nanocrystalline peak corresponding to ε-Ti₂N (3 1 1) with a crystallite size of 60 nm. Surface morphologies varied dramatically with N₂ pressure. The electrical resistivity of the film deposited at 12 mTorr was 37 MΩ cm whereas it is 270 kΩ cm for the films deposited at 25 mTorr. Therefore, the current work provides signatures for the ε-Ti₂N phase in terms of refractive index, optical absorption edge and electrical resistivity, that can be used to identify the presence of the sub-stoichiometric forms in a TiN film.