Takahiro Harada

Low-temperature deposition of optical films by oxygen radical beam-assisted evaporation

Abstract Titanium and silicon oxides were deposited as optical films on glass substrates at low temperature (below 100°C) by oxygen radical beam-assisted evaporation (RBAE). Ti and Si were used as the starting material. Conventional reactive evaporation using neutral oxygen gas was compared with RBAE. The optical properties (refractive index n , and extinction coefficient k ) and chemical structures of the deposited films were investigated. The radical beam source used in this study generated oxygen radicals with negligible ionic species. The films deposited by RBAE reached high oxidation states, compared with those deposited by conventional reactive evaporation. The n and k values of the films deposited by RBAE were almost constant over a wide range of Ti and Si evaporation rates. On the other hand, n and k values of the films deposited by conventional evaporation increased immediately with an increase in Ti and Si evaporation rates. An anti-reflective coating based on a multi-layer of TiO 2 and SiO 2 deposited by RBAE, which showed good performance in low reflectance and high transmittance, was demonstrated. It indicates that RBAE is an effective process for film deposition at low temperature.

Temperature measurement of polymer substrates during plasma irradiation

In the web coating process of some materials using sputtering, plasma-assisted evaporation, and plasma-enhanced C VD, heat damage of polymer substrates by plasma irradiation is problem for the quality of products. During deposition, the substrate is heated by condensation of deposits, heat from the source or plasmas, and so on. However, it is difficult to distinguish these processes and the change of the temperature plasma irradiation must be minimized. In this paper, we have researched the effect of discharge conditions on the plasma heating of the polymer substrate independently of the other heat sources. The Ar, O2 and N2 plasmas were created by AC discharge with magnetic field using web coating. PET(Polyethylene terephthalate) substrate was passed through the plasma region at different conditions, such as gaseous species, pressure, discharge power, and web speed. The temperature of the substrate was measured using thermometer before and after passing through the plasma region. In ordinary case, the temperature of the substrate increased immediately when the substrate entered the plasma region and had the maximum at the center of the plasma region. When the power input increased, the temperature slightly increased in both plasmas. Pressure also affected the increment of the substrate temperature. The change of the web speed influenced upon the residence time of the substrate in the plasma region. In this experimental conditions, although the temperature change of the substrate were 0.4–3°C, this would not ignore for the polymer substrate. The change of the substrate temperature passing through plasma region will be discussed together with the results of plasma diagnostics and some the surface analysis of the substrate.

High rate deposition of TiO2 and SiO2 films by radical beam assisted deposition ( RBAD)

Abstract Radical beam assisted deposition (RBAD) is an advanced and attractive technique compared with the conventional vacuum evaporation process. In this study, TiO 2 and SiO 2 films were deposited from Ti and Si metals onto glass substrate by RBAD. Atomic oxygen radicals were produced by a beam source using a RF plasma tube. The atomic oxygen radical beam flux (AORBF) density could be achieved to be more than 1×10 15 (atom cm −2 s −1 ). The refractive indices n of the TiO 2 films were higher than 2.35, and the extinction coefficients k were lower than 3×10 −3 at the deposition rate of 1.8 nm s −1 when the AORBF density was 8.4×10 15 (atom cm −2 s −1 ). For the SiO 2 film, n was 1.48, and k was lower than 1.5×10 −3 at the deposition rate of 2.4 nm s −1 . Moreover, n of the TiO 2 films could be increased to 2.50 by adding an ion beam flux to the radical beam flux. From these results, it is confirmed that TiO 2 and SiO 2 films deposited by RBAD have good optical properties even at higher deposition rates.