Single to polycrystalline transition in silicon growth by ion-assisted deposition at low temperatures

We investigate the microstructure of thin silicon films produced at temperature below, 450 degreesC by ion-assisted deposition. Our. transmission electron microscopy investigations show that in this temperature regime epitaxial growth breaks down at a critical film thickness beyond which the growth changes to polycrystalline or amorphous. The critical thickness increases with an increase in temperature. We use this effect that is well known from molecular beam epitaxy to analyze and quantify growth on silicon substrates with different surface normal orientations at various temperatures. Our results indicate that epitaxy works by far the best for the [001] surface normal orientation. The critical epitaxial thickness h(epi) decreases in the sequence h(epi)(001)>>h(epi)(113) >h(epi)(011)>h(epi)(111). The respective activation energies of 0.6, 2.1, 1.2, and 1.4 eV are evaluated from the temperature dependence. (C) 2003 American Institute of Physics.