Optical characterization of hydrogenated amorphous silicon thin films deposited at high rate
The aim of this paper is to provide a better understanding of hydrogenated amorphous silicon thin films (a-Si:H) in relation to their optical properties: refractive index, optical gap, absorption coefficient, thickness and surface roughness. The transmission spectrum of the films, deposited with various rf discharge power densities by an optimized plasma enhanced chemical vapor deposition (PECVD) method, at a high rate ({gt}10{angstrom}/sec), was measured over a range in wavelength from 500 to 1,100 nm. An approximate model is utilized to describe the surface roughness. In this model, the surface roughness is modeled as a mixed layer of 50% of a-Si:H and 50% of air and the optical constant of the rough layer is derived using the Bruggemann effective medium approximation (EMA). The gradient iteration method of numerical analysis is used to solve the nonlinear equations in the study. The results show that the potential underestimation of refractive index and resulting overestimation of film thickness can be overcome by considering the reflection of the rough surface. The method is carried out on the transmission data and the influence of rf discharge power density on the properties of the film is discussed in detail.
- Research Organization:
- City Univ. of Hong Kong, Kowloon (HK)
- OSTI ID:
- 20005402
- Journal Information:
- Journal of Electronic Materials, Vol. 28, Issue 12; Conference: 1999 TMS Annual Meeting, San Diego, CA (US), 02/28/1999--03/04/1999; Other Information: PBD: 12 Nov 1999; ISSN 0361-5235
- Country of Publication:
- United States
- Language:
- English
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