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.
New optical recording material for video disc system
The optical characteristics of Sb2Se3 and Sb2Te3 films are changed due to an amorphous‐crystalline phase transition below 200 °C. The respective reflectivity of 400 A Sb2Se3 and 300 A Sb2Te3 films, each on a Te reflective layer, is increased from 10% to 30% and from 45% to 65% by laser radiation. Using these new materials, optical disc recording of FM video signals by a diode laser has been demonstrated.
Ge Segregation during molecular beam epitaxial growth of Si1-xGex/Si layers
Abstract The growth of pseudomorphic Si 1− x Ge x layers (0.08 ⩽ x ⩽ 0.33) on Si (100) was studied by means of secondary ion mass spectroscopy and Rutherford backscattering spectrometry with glancing angle detection. The interfaces under growth conditions for epitaxy (substrate temperatures between 470 and 560 °C) were never atomically sharp but showed asymmetric smearing of the germanium towards the surface. The segregation is characterized by an inverse slope in the germanium profile of 17 nm per decade. The total amount of segragated germanium corresponds to between 0.2 and 0.5 monolayer. At lower temperatures the layers become rough, decreasing the crystalline quality, however, the interfaces as detected by secondary ion mass spectroscopy become much sharper. It is proposed that the smearing is due to a germanium ad-layer that is formed during the Si 1− x Ge x deposition and is incorporated slowly during further silicon growth.