Comparative studies between the growth characteristics of Bi2Te3 thin films deposited on SiO2, Si(100) and Si(111)
Thin films of Bi2Te3 on SiO2, Si(100) and Si(111) were deposited using a hot wall epitaxy (HWE) system. The growth conditions were optimized by the criterion of the highest mobility. XRD and SEM analysis show that the films obtained were stoichiometric and present a good morphology. No difference was observed between layers deposited on Si(100) and on Si(111): the layers were not sensitive to the initial orientation of silicon. The electrical measurements performed at room temperature show that the quality of layers deposited on SiO2 was better than the quality of layers deposited on Si(100) and Si(111). The figure of merit obtained in the case of the SiO2 substrate was Z = 1.9 × 10−3K−1, which is close to those reported for the monocrystal. The study of the first growing stage shows that the difference obtained between the substrates can be explained by the degree of reactivity of their surfaces.
Surfactant effect of H atoms on the suppression of Ge segregation in Si overgrowth on Ge(n ML)/Si(100) substrates by gas source molecular beam epitaxy
Hydrogen surfactant effect on the surface segregation of Ge atoms has been studied from layer-by-layer changes in the growth rate of Si overlayers on Ge/Si(100) substrates with Ge thicknesses of 0-6 ML by gas source molecular beam epitaxy using Si 2 H 6 . The layer-by-layer growth rates were in-situ measured by reflection high-energy electron diffraction (RHEED) intensity oscillation periods. The growth rate of Si overlayers decreases exponentially with increasing Si thickness and eventually approaches that of Si/Si(100) homoepitaxial growth at substrate temperatures of 440-550°C, which corresponds to the change in surface coverages of Ge atoms. The decay length of the surface concentration of Ge atoms is suppressed by an increase in Si 2 H 6 gas pressure. The temperature dependence of the decay length has an activation energy of 1.3 eV for Si 2 H 6 gas pressures of 5×10 -6 to 5×10 -5 Torr. These facts can be explained as an effect of H atoms existing on the surface
Is low temperature growth the solution to abrupt Si⧸Si1-xGex interface formation?
Abstract Si⧸Si1-xGex interface transients were investigated with respect to the absuptness and smoothness by using sputter depth profiling (SIMS), X-ray photoemissions (XPS), photoluminescence and transmission electron microscopy. Ge segregation was confirmed by blue-shift of luminescence energy above what is expected in a square well potential, along with SIMS measurement. Ge segregation was found to persist even at 300°C or lower. In contrast, Ge segregation was quenched by either segregant-assisted growth using Sb and Ga or solid-phase regrowth of Si cap layer; thereby a sharp Si⧸Si1-xGex interface was obtained. However, low-temperature-grown samples required an extensive anneal to restore band-edge luminescence, indicating a lack of quality of crystallinity.