The influence of the momentum transfer on the structural and optical properties of ZnSe thin films prepared by r.f. magnetron sputtering

Abstract

ZnSe films were deposited at room temperature by radio frequency magnetron sputtering onto [100] oriented silicon substrates. Under the same deposition conditions three sets of samples were produced by varying the sputtering pressure (0.4, 0.5 and 0.9 Pa), and changing the sputtering power supply in the range 25–150 W. The effect of the different growth conditions on the structural and optical properties was investigated by using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) Spectroscopy. In particular, the dependence of the coatings residual strain, texture, refractive index and extinction coefficient on the parameter β, proportional to the momentum transfer was studied. According to the results, the ZnSe coatings were grown almost exclusively in the cubic phase with a small percentage of very disordered ZnSe hexagonal phases. At low β values, the films were found in a tensile in-plane stress state, then a stress inversion from tensile to compressive occurred at β=27 a.u. and the films remained in a compressive state for momentum values β>27 a.u.