Anisotropic Laser-Induced Damage Threshold and Residual Stress of TiO<SUB>2</SUB> Sculptured Thin Films

Abstract

The residual stress and laser-induced damage threshold (LIDT) of TiO2 sculptured thin films prepared by glancing angle electron beam evaporation were studied. UV-Vis-NIR spectra and optical interferometer were employed to characterize the optical and mechanical properties, respectively. Optical microscopy and Raman spectra were used to observe damage morphology and analyze damage microstructure, respectively. It was found that the residual stress changed from compressive into tensile with increasing deposition angle. The LIDT was anisotropic with p- and s-polarization light, which was due to the anisotropic nanostructure and optical properties. Simultaneously, an optimum deposition angle for the maximum threshold of TiO2 film was about 60 degrees. The mechanism of laser-induced damage was thermal in nature. The process of thermal damage with crystallization is proved by Raman spectra.

Anisotropic vanadium dioxide sculptured thin films with superior thermochromic properties

“…It is known that phase transition temperature can be depressed by doping, finite size and inhomogeneous strain2829. For VO 2 STF without doping, films are porous with tilted columnar structure and the residual stress is huge30. It can be deduced that the depressed phase transition temperature may be resulted form inhomogeneous strain in film.…”