Highly reflective nc-Si:H/a-CNx:H multilayer films prepared by r.f. PECVD technique

Multilayer thin films consisting of a-CNx:H/nc-Si:H layers prepared by radio-frequency plasma enhanced chemical vapour (r.f. PECVD) deposition technique were studied. High optical reflectivity at a specific wavelength is one of major concern for its application. By using this technique, a-CNx:H/nc-Si:H multilayered thin films (3–11 periods) were deposited on substrates of p-type (111) crystal silicon and quartz. These films were characterized using ultra-violet–visible–near infrared (UV–Vis–NIR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, field effect scanning electron microscopy (FESEM) and AUGER electron spectroscopy (AES). The multilayered films show high reflectivity and wide stop band width at a wavelength of approximately 650 ± 60 nm. The FTIR spectrum of this multilayered structure showed the formation of Si–H and Si–H2 bonds in the nc-Si:H layer and CC and N–H bonds in a-CNx:H layer. SEM image and AES reveal distinct formation of a-CNx:H and nc-Si:H layers in the cross section image with a decrease in interlayer cross contamination with increasing number of periods.