Scanning tunneling microscopy study of rough Si films deposited on Si(111)

Series of silicon films were grown by thermal evaporation on Si(1 1 I)substrates at temperatures between similar to 240 degreesC and similar to 500 degreesC under ultrahigh-vacuum conditions, and examined with scanning tunneling microscopy. Two series of films grown at similar to 240 degreesC and similar to 400 degreesC showed a trend toward multilayer root-mean-squared (rms) roughness as thicknesses of tens to hundreds of bilayers were reached. The roughening of the similar to 240 degreesC deposition series appeared to slow as thicker films were deposited; the effective power law for the rms roughness suggested by measurement of the thinner films was t(0.4 +/-0.1), which is faster than that consistent with linear diffusion dynamics. The growth at similar to 400 degreesC appeared to be multilayer epitaxial and showed an increase in lateral feature size with deposition time. At higher deposition temperatures of similar to 450 degreesC and similar to 500 degreesC. a flatter terraced morphology with dotted depressions was seen, Some of these vacancies appeared in straight lines, usually running parallel to the rough steps, indicating a pinning effect on the growing film due to the initial substrate step morphology. The degree of pinning was analyzed in the framework of the directed-percolation depinning model. The roughening behavior exhibited by the films in this study results from a pinning effect and is attributed partially to the incorporation of carbon and oxygen in these films. (C) 2001 Published by Elsevier Science B.V.