Strong amorphization of high-entropy AlBCrSiTi nitride film

Abstract

Amorphous coatings, particular nitride systems, are of interest for numerous practical applications. Nevertheless, at present only a few amorphous nitride coating systems have been considered, the most notably being the (TM, Si)N system (transition metal (TM)=Ti, Zr, W, Mo). The present study provides an alternative approach for producing amorphous nitride films with high thermal stability up to 700°C for 2h. Films are deposited from an equimolar AlBCrSiTi target in various argon/nitrogen atmospheres at different substrate temperatures. It is found that above the nitrogen flow ratio (i.e. RN=N2/N2+Ar) of 28.6% a near equal ratio between target elements and nitrogen is approached, thus indicating the coatings have the chemical formula of (AlBCrSiTi)N. The glancing-angle X-ray diffractometer and transmission electron microscope investigations indicate that the coatings, regardless of nitrogen concentration or deposition temperature (up to 500°C), are amorphous. Thermal treatment shows that the amorphous structure of this (AlBCrSiTi)N coating is maintained up to 700°C when annealing for 2h in vacuum. At annealing temperatures of 800°C and above, the amorphous films transform into a simple NaCl-type face-centered cubic solid solution. Even after annealing at 1000°C for 2h, the grain size is only 2nm. High entropy effect, large lattice distortion effect, and sluggish diffusion effect are proposed to account for the formation of amorphous nitrides.