Texture evolution of vanadium nitride thin films

Abstract

Abstract The purpose of this research was to investigate the applicability of competitive growth theory on the texture evolution of vanadium nitride (VN) thin films, and the effect of texture on the mechanical properties of VN thin films was also studied. VN thin films were deposited using unbalanced magnetron sputtering. The preferred orientation was controlled by adjusting nitrogen flow rate, deposition temperature, substrate bias, and target current. For the VN thin films with texture ranging from (200) to random (group I), the preferred orientation gradually changed from (200) to random texture with increasing nitrogen flow rate. VN thin films with (111)-dominant texture (group II) could be deposited with increasing nitrogen flow rate and under low energy conditions with lower temperature, substrate bias and target current. Considering the similarity of atomic configuration, the formation of (200) plane of VN (NaCl structure) may follow the (110) preferred atomic configuration in body-centered cubic-structure vanadium base metal. In addition to the competitive growth theory, the steering effect due to base metal structure may be an important factor for the texture evolution of the corresponding transition-metal nitrides. The accompanying microstructure and mechanical properties were also divided into two groups following texture coefficient. The film microstructure in group I belonged to zone T structure with dense columnar structure and smooth surface, while that in group II had zone I structure with loose columnar structure and rough surface. The film hardness in group I was about 30\u202fGPa and weakly texture-dependent, while that in group II was quite low and texture dependent ranging from 5.7 to 11.4\u202fGPa. The residual stress of films in region I decreased from −5.66 to −2.66\u202fGPa with increasing (111) texture coefficient, while that in group II was mostly relieved due to loose microstructure, ranging from −0.44 to 0.45\u202fGPa. The electrical resistivity of the understoichiometric samples was higher than that of stoichiometric samples except for the sample with (111)-dominant texture. In addition, loose-packed microstructure also causes higher electrical resistivity.