Papers by Keyword: Growth

Abstract: Thin (200-600 nm) Si-Sn alloy films were grown under ultrahigh vacuum conditions by co-deposition of Si and Sn on the Si (100) substrate at room temperature. Investigations of the film structure by X-ray diffraction showed the preservation of the amorphous structure of Si-Sn films without the contribution of the Si_1-xSn_x alloy with sphalerite lattice at Sn concentration in the range of x=0.14-0.19. Analysis of optical spectra and calculations showed that an amorphous Si-Sn film with a Sn concentration of 19% is a semiconductor with indirect fundamental optical transition with very high absorption at photon energies 0.2 – 1.0 eV. It was found that precipitation of β-Sn occurs with an increase of Sn concentration up to 40%, which is accompanied by an increase in the reflection coefficient to 0.6-0.8 at photon energies below 0.8 eV. The limited temperature stability of amorphous Si-Sn films is shown for high-energy and long-term (10 minutes) laser irradiation due to the formation of metallic precipitates of β-Sn.

Abstract: Optical reflection spectra in the photon energy range of 1.5-6 eV have been studied after the growth of ultrathin iron films on silicon (001) in the 0-1.2 nm thickness range. It has been noted that the reflection coefficient values vary nonmonotonically in thickness near the limiting energy of 1.5 eV and 6 eV. Moreover, they are abnormally large one at 1.5 eV and small one at 6 eV. It is shown that these phenomena can not be explained by simple models of the formation of a metallic, silicide film or amorphous silicon layer at the interface and correspond to structural-phase transformations in the film and in the substrate interface region.

Abstract: A wetting layer with a nanophase structure was detected and identified before the first bulk phase during the formation of the metal-silicon interface by vapor-phase deposition at room temperature of the substrate. This became possible due to the developed technique for complex analysis of the structural-chemical state of the surface/ interface with help of Auger electron spectroscopy and electron energy loss spectroscopy, and also due to the method of physical vapor deposition at low temperature of vapor. The discovery this wetting layer and stage of its formation fundamentally changes the approach to the formation of contact between metal and silicon.

Abstract: The growth, structure, optical, electrical and thermoelectric properties of calcium silicides of various compositions on silicon substrates with (100) and (111) orientations were experimentally studied. It was found that when the atoms of Ca and Si are co-deposited on atomically clean silicon, the basis phases in the composition of the formed films depends on the substrate temperature and the annealing temperature: Ca₂Si (T_Si = 20°C, T_ann = 330°C), CaSi (T_Si = 190-320°C, T_ann = 330°C) and CaSi₂ (T_Si = 500°C). It was established that the Ca₂Si phase is a direct-gap semiconductor with a band gap of 0.82±0.02 eV, large contribution of defect levels to the absorption coefficient at energies 0.25 - 0.50 eV and huge transmission up 90% in the far IR region. In CaSi-based films the high transmission (30-40%) up to 25 μm was observed, which corresponds to a semimetal with a constant density of states near the Fermi level. It was found that CaSi-based films have the maximum Seebeck coefficient and the power factor (up to 430 μV/K and up to 1.14 × 10^-6 W/(K²m), respectively) at 330K. CaSi₂ films with CaSi₂ lattice stretching and epitaxial ordering relative to the Si (100) substrate exhibit semimetal properties, with very high conductivity and light transparency (up 12%) in the photon energy range 0.06 - 0.65 eV.

Abstract: We investigated effects of spacing and no. of seedling hill^-1 on growth and yield component of rice cv. Chai Nat 1 in system of rice intensification. The experiment included 25 × 25 cm, 30 × 30 cm, 40 × 40 cm, and 50 × 50 cm with single seedling hill^-1, two seedlings hill^-1, and three seedlings hill^-1, respectively. The study was in Kasetsart University Chalermphrakiat Sakonnakhon Province Campus during November 2016 to March 2017. Each condition was laid out in a randomized completed block design with three replications. The experiment found that the no. of seedlings hill^-1 influence in the growth and the yield component of the rice, while the spacing does not. Moreover, there is no interaction between spacing and seedlings hill^-1. The three seedling hill^-1 condition showed the highest in tillering (avg. = 24.13 tillers hill^-1). The single seedling hill^-1 showed the lowest in tillering (avg. = 16.24 tillers hill^-1). From this research indicated that optimized seed hill^-1 in rice cultivated system.

Abstract: The initial stages of copper electrodeposition in acid copper sulphate/sodium citrate bath were investigated with varying copper and sodium citrate concentrations. Different electrochemical measurements, including linear sweep voltammetry, cyclic voltammetry, and chronoamperometry were introduced to the study. The Scharifker-Hills model was introduced to identify the nucleation model with analysing current transients. It was observed that the increase of copper ions inhibited the cathodic polarization behaviour for the reduction of ions. On the contrary, sodium citrate promoted the cathodic polarization behaviour. The chronoamperometry results indicated that without the sodium citrate, the nucleation process corresponded to instantaneous nucleation and three-dimensional diffusion limited growth, although obvious deviations were observed. While the addition of sodium citrate changed the deviations and caused that the initial deposition kinetics followed well with the mechanism of instantaneous nucleation.

Abstract: The saturation of primary tensile twins in heavily textured Mg-alloy AZ31 is investigated, and their strain accommodation limit is evaluated. EBSD results suggest that the mean number of twins per grain saturate rapidly, followed by the stop of twin growth. Twinning saturation is included in a physical model of twin evolution.

Abstract: In Vitro shoot culture of Bulbophyllum dhaninivatii Seidenf. was conducted on semi-solid Vacin and Went (1949) medium supplemented with coconut water (50 100 and 150 ml/L), potato extract (25 and 50 g/L) and banana homogenate (25 and 50 g/L) for 12 weeks. The results found that the highest shoot number (6.92 shoots) could observe on the medium supplemented with 150 ml/L coconut water, 50 g/L potato extract and 50 g/L banana homogenate while the highest leaf and root number could obtain when cultured on the medium supplemented with 100 ml/L coconut water, 50 g/L potato extract and 50 g/L banana homogenate.

Abstract: The results of the studies of phase formation and the structural state of diffusional zinc coatings formed in zinc powder with nanocrystallized surface of the particles are presented. The sequence of iron-zinc phases formation during the process has been established, which is the reciprocal of those obtained during the annealing of "hot dip" coatings. The microstructure of δ-phase in the coating, a change in its texture and structural parameters through the thickness of the coating have been studied.

Abstract: InAs nanowires (NWs) is a key material for high-speed electronics, near-and mid-infrared light emission and detection applications. Much effort has been devoted to the fabrication of InAs NWs and molecular beam epitaxy (MBE) evolved as a powerful method to grow semiconductor nanowires with several interesting features, but it was rarely reported. We present kinds of growths (metal-catalyzed growth, self-catalyzed growth, self-induced free-standing growth, self-induced position-controlled growth, self-assisted nucleation growth etc.) of InAs NWs by MBE, and discuss how to control growth of uniform-structure InAs NWs on homogeneous or heterogeneous substrates, which can provide the reference for the manufacture of low dimensional structure.