Structure of reactively magnetron sputtered Hf-N films

Abstract

In spite of the technical interest in the Hf-N system the form of the phase diagram is not yet clear, and therefore it is difficult to predict the phase composition of thin films. In this letter Hf-N films have been prepared by reactive dc planar magnetron sputtering and the phase composition of the films investigated by x-ray diffraction. Between the α-Hf and HfN single phase regions a multiphase region was found consisting of α-Hf, ε-Hf3N2, and/or ζ-Hf4N3 and also HfN in the nitrogen rich part. For the mononitride a lattice parameter of 4.54 Å was found which is slightly higher than reported bulk vlaues. This deviation is caused by intrinsic stresses in the films. If the nitrogen content is increased above that of the mononitride, the (111) interplanar distance increases further while all other interplanar distances decrease. At still higher nitrogen contents new reflections start to appear indicating a new phase. In this region the films also change from being conducting and nontransparent to electrically insulating and transparent.