Silver Thin Film Deposited By Arc Ion Plating Technique

Silver (Ag) film is one type of the high reflection films. When it is used in the short wavelength region of the visible and the far ir, it has the optical characteristics of high reflectance and low absorbance. Ag film is usually made by the technology of thermal evaporation (TE).However, due to the low energy of the target atoms by TE and Ag film’s low adhesion property with the glass substrate, the density of such Ag film is not good enough and easier to be oxidized. Arc ion plating (AIP) displays several great features, such as high ionization degree, high ion kinetic energy, high film density, high adhesion and so on. It has been widely used in the field of deposition for hard thin films. However, researches no AIP applications for Ag film are rare.In this dissertation, Ag films were deposited on K9 glass and silicon substrate by magnetic filter arc source deposition (MFASD) technology, using Ag material with purity of 99.99%. The deposition rate, surface roughness and adhesion of the as-deposited Ag films were measured by white-light interferometer, spectrophotometer and stripping test respectively. This study was mainly to investigate the following aspects:1) the discharging of Ag target in arc environment, 2) the deposition rate, uniformity and surface roughness of Ag films respect to the target current, 3) the deposition rate and surface roughness of Ag films respect to the bias of substrate,4) impact of seed layer to adhesion of Ag film. The results are shown as follows:In the experiments, the deposition rates of Ag films range from 0.3412 nm/s to 2.048 nm/s, which depend on the target current and bias of substrate. When the target current increase, the deposition rate increases accordingly, surface roughness improved and deposition area enlarged as well. Bias of substrate also affects the quality of film, for the surface roughness, a minimum value of 0.5355 nm was get at a bias of+10 V on silicon substrate. The result on peeling test showed that the adhesion of Ag films deposited by AIP is also improved for both single layer Ag film and Al2O3-Ag film.With large energy ion assisting deposition,30nm Al2O3 was deposited first on the substrate which act as the buffer layer and protection layers of 30 nm Al2O3 and 200 nm SiO2 was also deposited on the Ag film. Such Ag film based multi-layer structure shows enough strength for application as optical film.