Tilt boundary formation in GeSi/Si (001) vicinal heterosystem

The structural state of GexSi1-x films grown on Si substrates with the vicinal orientation (1 1 13) has been studied. The (1 1 13) orientation has been obtained by rotating the singular plane (001) around the [1 1 ¯0] axis. The x parameter of GexSi1-x films in different samples ranged from 0.083 to 0.268. Triclinic distortions arising in film crystal lattice have been analyzed using our technique developed for the determination of epitaxial layer structural parameters based on the X-ray diffractometry data. It has been established that during the epitaxial process the film lattice turns around the direction of surface steps due to the introduction of misfit dislocations into the interface. Dislocations with Burgers vector a/2〈110〉 which is not parallel to the interface create an analog of a tilt boundary. The turning angle value ψ is proportional to the misfit dislocation density. This phenomenon is associated with a decrease of the interface symmetry that leads to a change in the efficiency of stress relieving by dislocations belonging to different families. The influence of these families on the low-angle boundary formation is considered. Experimental values of the ψ angle and shear strain for the [13 13 2¯] and [1¯ 1 0] directions lying in the interface (1 1 13) have been defined. A comparison of the experimental and calculated values of ψ for the [13 13 2¯] direction is provided

Formation of SnO and SnO2 phases during the annealing of SnO(x) films obtained by molecular beam epitaxy

SnO and SnO2 films were obtained on the SiO2 surface by the molecular-beam epitaxy method. The initial film

Morphology, structure, and optical properties of SnO (x) films

The paper presents the morphological, structural, and optical properties of nanostructured SnO (x) film

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

Elastically strained GeSiSn layers and GeSiSn islands in multilayered periodical structures

This work deals with elastically strained GeSiSn films and GeSiSn islands. The kinetic diagram of GeSiSn growth for different lattice mismatches between GeSiSn and Si has been drawn. The multilayered periodic structures with pseudomorphic GeSiSn layers and GeSiSn island arrays have been obtained. The density of the islands in the GeSiSn layer is 1.8 · 1012 cm-2 for an average island size of 4 nm. Analysis of the rocking curves has shown that the structures contain smooth heterointerfaces, and no abrupt changes of composition and thickness between periods have been found. Photoluminescence has been demonstrated and calculation of band diagram with the model-solid theory has been carried out. Luminescence presented for sample with pseudomorphic Ge0.315Si0.65Sn0.035 layers in the narrow range 0.71–0.82 eV is observed with the maximum intensity near 0.78 eV corresponding to 1.59 µm wavelength. Based on the band diagram calculation for Si/Ge0.315Si0.65Sn0.035/Si heterocomposition we have concluded that 0.78 eV photon energy luminescence corresponds to interband transitions between the X-valley in Si and the heavy hole subband in the Ge0.315Si0.65Sn0.035 layer

Dislocation Filter Based on LT-GaAs Layers for Monolithic GaAs/Si Integration

The use of low-temperature (LT) GaAs layers as dislocation filters in GaAs/Si heterostructures (HSs) was investigated in this study. The effects of intermediate LT-GaAs layers and of the post-growth and cyclic in situ annealing on the structural properties of GaAs/LT-GaAs/GaAs/Si(001) HSs were studied. It was found that the introduction of LT-GaAs layers, in combination with post-growth cyclic annealing, reduced the threading dislocation density down to 5 × 106 cm−2, the root-mean-square roughness of the GaAs surface down to 1.1 nm, and the concentration of non-radiative recombination centers in the near-surface GaAs/Si regions down to the homoepitaxial GaAs level. Possible reasons for the improvement in the quality of near-surface GaAs layers are discussed. On the one hand, the presence of elastic deformations in the GaAs/LT-GaAs system led to dislocation line bending. On the other hand, gallium vacancies, formed in the LT-GaAs layers, diffused into the overlying GaAs layers and led to an increase in the dislocation glide rate. It was demonstrated that the GaAs/Si HSs obtained with these techniques are suitable for growing high-quality light-emitting HSs with self-assembled quantum dots