Deposition at room temperature of Ga on Si(100) produces single-atom-wide metal rows orthogonal to the Si-dimer rows. Detailed analysis using scanning tunneling microscopy reveals a monotonically decreasing size (i.e., length) distribution for these rows. This is unexpected for homogeneous nucleation without desorption, conditions which are operative in this system. Kinetic Monte Carlo simulation of an appropriate atomistic model indicates that this behavior is primarily a consequence of the feature that the capture of diffusing atoms is greatly inhibited in the Ga∕Si(100) system. The modeling also determines activation barriers for anisotropic terrace diffusion, and recovers the experimental distribution of metal rows. In addition, we analyze a variety of other generic deposition models and determine that the propensity for a large population of small islands in general reflects an enhanced nucleation rate relative to the aggregation rate.
Disciplines
Chemistry
CommentsThis article is from Physical Review B 72 (2005) Deposition at room temperature of Ga on Si͑100͒ produces single-atom-wide metal rows orthogonal to the Si-dimer rows. Detailed analysis using scanning tunneling microscopy reveals a monotonically decreasing size ͑i.e., length͒ distribution for these rows. This is unexpected for homogeneous nucleation without desorption, conditions which are operative in this system. Kinetic Monte Carlo simulation of an appropriate atomistic model indicates that this behavior is primarily a consequence of the feature that the capture of diffusing atoms is greatly inhibited in the Ga/ Si͑100͒ system. The modeling also determines activation barriers for anisotropic terrace diffusion, and recovers the experimental distribution of metal rows. In addition, we analyze a variety of other generic deposition models and determine that the propensity for a large population of small islands in general reflects an enhanced nucleation rate relative to the aggregation rate.
In situ scanning tunneling microscopy and x-ray photoelectron spectroscopy were combined to examine the formation of the Fe/GaAs interface for Fe films grown on GaAs(100) As-rich surfaces by molecular beam epitaxy. Scanning tunneling microscopy images acquired following the growth of ultrathin layers of Fe on GaAs (2×4)/c(2×8)β2 surfaces show the initial growth of Fe results in little disruption of the As-dimer rows located directly adjacent to the deposited Fe clusters for growth temperatures between −15 and 175 °C. X-ray photoemission spectra show the interfacial Fe–Ga–As reactions depend on the growth temperature and can be minimized by growing at temperatures below 95 °C. However, approximately 0.7 ML of As was found to segregate to the Fe surface during growth, independent of the growth temperature. Atomic layer-by-layer calculations of the normalized intensity curves obtained from x-ray photoemission were used to quantify the extent of the interfacial reactions as a function of growth temperature. A 5 ML thick (∼14 Å) ErAs interlayer was used as a diffusion barrier to further limit the Fe–Ga–As interfacial reactions. For Fe growth at 225 °C on ErAs interlayers, the extent of the interfacial reactions was found to be comparable with the extent of the reactions resulting from the growth of Fe directly on GaAs at −15 °C. Although the ErAs interlayers suppressed the reactions between Fe and GaAs at the interface, they were unable to significantly alter the amount of As segregating to the Fe surface during growth.
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