Brent A. Sperling, John R. Abelson
Kinetic roughening of amorphous silicon during hotwire chemical vapor deposition at low temperature
Journal of Applied Physics 101 (2007) 024915
We use postdeposition atomic force microscopy and in situ spectroscopic ellipsometry to analyze the roughening of hydrogenated amorphous silicon films deposited by hotwire chemical vapor deposition at 150 °C. From the atomic force microscopy data, the rootmeansquared roughness w increases with deposition time t as w proportional to t^{β} with β=0.37 +/ 0.02, and the correlation length ξ increases as ξ proportional to t^{1/z} with 1/z=0.31 +/ 0.02. From the heightdifference correlation function, we obtain a roughness exponent α=0.87 +/ 0.04 and a rootmeansquared local slope delta, which increases as δ proportional to t^{κ} with κ=0.17 +/ 0.03. These measurements are indicative of anomalous growth, which we attribute to geometric shadowing. However, the roughening behavior we observe using atomic force microscopy is not reproduced in the spectroscopic ellipsometry data. This contradicts previous reports which found a linear relationship between the thickness of the optical roughness layer and the rootmeansquared roughness. We discuss the discrepancy between the two techniques in terms of shortrange roughness and vector perturbation theory.
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