Stress, texture and microstructure of zirconium thin films probed by X-ray diffraction

Abstract

Zirconium ( α-Zr) thin films (thicknesses: 12 nm–240 nm) have been deposited on glass substrates by dc magnetron sputtering. Anisotropic broadening of diffraction lines has been observed for all films when probed by X-ray diffraction. Williamson–Hall method of X-ray line profile analysis shows average crystallite sizes of a few nanometers and high average microstrains for all films. Diffraction stress analysis of Zr films reveals relatively high biaxial compressive stresses that are found to decrease with increasing film thickness. The level of stress has been compared to the theoretical yield strength of Zr films obtained by a model calculation. All Zr films show (0002) fiber texture as dominant texture component except 240 nm thick films. Ratios of strain-free lattice parameters ( c o/ a o) determined for all Zr films are higher than the reported c o/ a o ratio for bulk zirconium. Observation of anisotropic diffraction line broadening in the textured Zr films with high in-plane compressive stress indicates anisotropy in the shape of individual crystallite in all films.