| Single-crystal Si films have been grown on Si(001)2x1 substrates by UV-photostimulated atomic-layer epitaxy (ALE) from Si{dollar}sb2{dollar}H{dollar}sb6.{dollar} The ALE deposition rate R per growth cycle remains constant at 0.43 monolayers (ML), 1 ML = {dollar}6.8times10sp{lcub}14{rcub}{dollar} cm{dollar}sp{lcub}-2{rcub}{dollar}, over a wide range of deposition parameters: growth temperature (T{dollar}sb{lcub}rm S{rcub}{dollar} = 180-400{dollar}spcirc{dollar}C), Si{dollar}sb2{dollar}H{dollar}sb6{dollar} exposure, UV laser energy density, and number of UV laser pulses per cycle. A film growth model, based upon the results of adsorption/desorption measurements, film growth experiments, and Monte Carlo simulations, is used to describe the reaction pathway for the process.; Si{dollar}sb2{dollar}H{dollar}sb6{dollar} is dissociatively adsorbed on Si surface dimers as two SiH{dollar}sb3{dollar} radicals which, as shown by electron energy loss spectroscopy (EELS) and reflection high-energy electron diffraction (RHEED), subsequently dissociate to SiH{dollar}sb2{dollar} and H. The saturated H-terminated surface is stable and passive to further Si{dollar}sb2{dollar}H{dollar}sb6{dollar} exposure. ArF or KrF laser pulses {dollar}(simeq{dollar}20 ns) are used to desorb H, following a Si{dollar}sb2{dollar}H{dollar}sb6{dollar} exposure, and the growth is repeated until the desired film thickness is obtained. Transmission electron microscopy (TEM) and cross-sectional TEM together with selective area and convergent-beam electron diffraction patterns show that the ALE films are epitaxial layers with no observed extended defects or strain.; The Si{dollar}sb2{dollar}H{dollar}sb6{dollar} sticking probability at 25{dollar}spcirc{dollar}C is found to be {dollar}simeq{dollar}0.5 while the saturation coverage is {dollar}simeq{dollar}0.5 ML on Ge(001)2x1. Scanning tunneling microscopy (STM) observations show the adsorbed overlayers exhibit regions of local ordering, in contrast to the case for Si{dollar}sb2{dollar}H{dollar}sb6{dollar} on Si(001), and are composed of SiH{dollar}sb2{dollar} and GeH with evidence of residual SiH{dollar}sb3.{dollar} Hydrogen desorption is observed at temperatures as low as 150{dollar}spcirc{dollar}C, admolecules are mobile at 270{dollar}spcirc{dollar}C, and complete ordering is observed by 330{dollar}spcirc{dollar}C. Film growth on Ge(001) is observed to proceed via a mixed mode. |
