Strong amorphization of high-entropy AlBCrSiTi nitride film

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 degrees C for 2 h. 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. R-N = N-2/N-2 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 degrees C), are amorphous. Thermal treatment shows that the amorphous structure of this (AlBCrSiTi)N coating is maintained up to 700 degrees C when annealing for 2 h in vacuum. At annealing temperatures of 800 degrees C and above, the amorphous films transform into a simple NaCl-type face-centered cubic solid solution. Even after annealing at 1000 degrees C for 2 h, the grain size is only 2 nm. High entropy effect, large lattice distortion effect, and sluggish diffusion effect are proposed to account for the formation of amorphous nitrides. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.