Complex optical filter prepared by sputter deposition

Abstract

An infrared heat reflecting multilayer thin film filter comprising alternate layers of ZrO2 and SiO2 has been modeled and prepared on a BK7 glass substrate using RF-magnetron sputtering. Initially, the individual films of the used materials have been characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) for structural and surface quality prior to the deposition of multilayer structure. Spectral analysis showed that the filter has an average transmission of greater than 90% in 450 to 700 nm range and less than 2% in 700-1100 nm band fulfilling the design requirements. The XRD study of multilayer structure showed few peaks of ZrO2 along with a solitary peak for SiO2 indicating some crystallinity for ZrO2 layers in the structure. Hardness analysis showed that the initial phase of the indentation is predominantly ductile with gradual transition in behaviour from ductile to brittle with increased penetration. Interface analysis of multilayered structure was carried out by Rutherford back scattering using Tandem 5 MeV ion accelerator, showed that interfaces formed in the multilayer structure are sharp and no substantial evidence of interlayer diffusion or mixing at the interfaces.