Equilibrium concentration of kinks on the SB steps of the Si(100) surface

The temperature and time dependences of the concentration of kinks on the S-A and S-B steps perpendicular to the upper-terrace dimer rows on the Si(100) surface with an inclination of 0.5 degrees are established. The numbers of step kinks are determined from atomic-resolution scanning tunneling microscopy images of the stepped Si(100) surface. It is shown that the temperature dependence of the number of kinks has a minimum at 650 degrees C. It is suggested that, at low temperatures, the steps are intensively smoothed (step kinks vanish), while at high temperatures, the step-destruction process (formation of a great number of step kinks) is more intensive. The step smoothing and destruction processes include a sequence of atom and dimer elementary acts. As the annealing time increases, the kink concentration decreases and takes a constant value. The equilibrium step-kink concentration is shown to be determined by the surface annealing temperature and time

Morphology, Structure, and Optical Properties of Semiconductor Films with GeSiSn Nanoislands and Strained Layers

Abstract The dependences of the two-dimensional to three-dimensional growth (2D-3D) critical transition thickness on the composition for GeSiSn films with a fixed Ge content and Sn content from 0 to 16% at the growth temperature of 150 °С have been obtained. The phase diagrams of the superstructure change during the epitaxial growth of Sn on Si and on Ge(100) have been built. Using the phase diagram data, it becomes possible to identify the Sn cover on the Si surface and to control the Sn segregation on the superstructure observed on the reflection high-energy electron diffraction (RHEED) pattern. The multilayer structures with the GeSiSn pseudomorphic layers and island array of a density up to 1.8 × 1012 cm−2 have been grown with the considering of the Sn segregation suppression by the decrease of GeSiSn and Si growth temperature. The double-domain (10 × 1) superstructure related to the presence of Sn on the surface was first observed in the multilayer periodic structures during Si growth on the GeSiSn layer. The periodical GeSiSn/Si structures demonstrated the photoluminescence in the range of 0.6–0.85 eV corresponding to the wavelength range of 1.45–2 μm. The calculation of the band diagram for the structure with the pseudomorphic Ge0.315Si0.65Sn0.035 layers allows assuming that photoluminescence peaks correspond to the interband transitions between the X valley in Si or the Δ4-valley in GeSiSn and the subband of heavy holes in the GeSiSn layer

Morphology, structure, and optical properties of semiconductor films with GeSiSn nanoislands and strained layers

The dependences of the two-dimensional to three-dimensional growth (2D-3D) critical transition thickness on the composition for GeSiSn films with a fixed Ge content and Sn content from 0 to 16% at the growth temperature of 150 °С have been obtained. The phase diagrams of the superstructure change during the epitaxial growth of Sn on Si and on Ge(100) have been built. Using the phase diagram data, it becomes possible to identify the Sn cover on the Si surface and to control the Sn segregation on the superstructure observed on the reflection high-energy electron diffraction (RHEED) pattern. The multilayer structures with the GeSiSn pseudomorphic layers and island array of a density up to 1.8 × 1012 cm−2 have been grown with the considering of the Sn segregation suppression by the decrease of GeSiSn and Si growth temperature. The double-domain (10 × 1) superstructure related to the presence of Sn on the surface was first observed in the multilayer periodic structures during Si growth on the GeSiSn layer. The periodical GeSiSn/Si structures demonstrated the photoluminescence in the range of 0.6–0.85 eV corresponding to the wavelength range of 1.45–2 μm. The calculation of the band diagram for the structure with the pseudomorphic Ge0.315Si0.65Sn0.035 layers allows assuming that photoluminescence peaks correspond to the interband transitions between the X valley in Si or the Δ4-valley in GeSiSn and the subband of heavy holes in the GeSiSn layer

Effect of annealing temperature on the morphology, structure, and optical properties of nanostructured SnO(x) films

Fabrication and characterization of titanium dioxide (TiO2) thin film on Al/TiO2/SiO2/p-Si MIS structure for the study of morphology, optical and electrical properties were reported. A transparent and high crystallinity of TiO2 thin films were prepared at room temperature (~25 °C) by sol–gel route. TiO2 sol suspension were prepared at molar ratio of TTIP:EtOH:AA = 2:15:1 using titanium tetra-isopropoxide (TTIP) and a mixture of absolute ethanol (EtOH) and acetic acid (AA) which used as a precursor and catalyst for the peptization, respectively. The TiO2 thin films were deposited on a thermally grown SiO2 layer of p-type silicon (100) substrates and were thermally treated at different annealing temperatures of 300, 500, 700 and 900 °C. For study of optical properties, the TiO2 thin films were deposited on a glass slides substrate and were annealed from 200 to 700 °C. The XRD results show that the presence of an amorphous TiO2 phases were transformed into the polycrystalline (anatase or rutile) with good crystallinity after treated at higher annealing temperatures. Besides, the surface roughness of TiO2 thin films increased with increasing annealing temperatures. In addition, the resistivity of the thin films decreased from 2.5751E+8 to 6.714E+7 Ω cm with the increasing temperatures. Moreover, the optical absorbance of TiO2 thin films exhibited high UV–visible light absorption with band gap energy shifted to the higher wavelength (low energy photons). The band gap energy (Eg) of the films decreased from 3.79 to 3.16 eV and from 3.95 to 3.75 eV significantly for direct band allowed and indirect band allowed, respectively, with the increasing annealing temperatures