Structural-Color-Control by AlN Coating on Rough-Surface Al Film

Abstract

(99.9995%) and N2 (99.999%) or the pure Ar was used as sputtering gas. The total working gas pressure (Ptot) was 1.33 Pa, which was the sum of the partial pressure of N2 (PN2) and that of Ar. In order to change the composition of the film, the concentration of partial N2 gas pressure (cN2=100� PN2=Ptot) was changed. Transparent AlN film was obtained at cN2=12%N2. 7) Of course the pure Al film was formed without N2. Corning #7059 glass (0.7 mm in thickness) was used as a substrate. Film thickness was measured using a surface texture measurement instrument (Surfcom 200B, Tokyo Seimitu Ltd.). The deposition rates were estimated by using smooth films with the thickness less than 100 nm. The typical deposition rates at input power of 200 W were 0.18 and 0.13 nm/s at 0 and 12%N2, respectively. Then in this study each film (or layer) is named by its substance, deposition film thickness (d) which is estimated by deposition rate, and substrate temperature (Tsub), e.g., a notation of Al(d ,T sub) represents an aluminum film with a thickness of d deposited at Tsub. Surface morphology was observed using an atomic force microscope (AFM: Nanopics, NPX100AFM head, Seiko Instruments Inc.). Optical properties of the specimens were measured using an ultraviolet-visible-near infrared spectrometer (UV-3100PC, Shimadzu Co.) in the wavelength range of 0.24 to 2.60 mm. The specular reflectance (R0) was evaluated by measuring the reflectance at an incidence angle of 12 � . The diffusive reflectance (Rd) at normal incidence was also measured using an integrating sphere with a diameter of 60 mm. The color photograph of specimen is taken using a digital camera (Digital Revio KD-300Z, Konica Co.). 3. Results