Papers by Keyword: MBE

Abstract: In this manuscript, the structural properties such as the distance inter-reticular of samples is studied, In the fact, four samples were used symbolized as follows: E tAg(Å), the only difference is the thickness of the Silver buffer layer (tAg= 0, 50, 100 and 150 Å) to find out how the thickness of this layer depends on the structural characteristics of the Iron thin layer, all samples are deposited using molecular beam epitaxy (MBE) at room temperature onto Si (100) substrate. The structural properties of all samples examined using X-ray diffraction method at small and high angles. The small angles X-Ray diffraction curves confirmed to us that there is a clear difference between the surface structure of the samples by varying the number of Kiessig Fringes, Also high angles X-Ray diffraction curves assured us this difference through the clear variation in the angular positions of the peaks of Bragg and the distances inter-reticular values from a sample to the other.

Abstract: Electromagnetic techniques such as Magnetic Hysteresis Loop and Barkhausen Emission are applied to determine recovery and recrystallization in low carbon IF steel. Isothermal annealing at 450 and 620°C are carried to promote recovery and recrystallization. In present study, the magnetic non-destructive parameters such as coercivity and magnetic Barkhausen noise signal measurements, recovery and onset of recrystallization are monitored for annealing treatments. Mechanical softening is very small changes than magnetic softening at 450°C, while at 620°C, both the parameters are sensitive. Microstructure analysis examined through Optical microscopy at each annealing temperature in order to determine recovery and recrystallization. Keywords: IF steel, Recrystallization, MHL, MBE, Hardness, Optical microscopy

Abstract: The in-situ monitoring of the MBE grown nanostructures can be carried out using the RHEED method. During the droplet epitaxal growth, the observation of the nanostructure formation is very important to understand the growth kinetics. In the present work, a novel in-situ RHEED evaluation and further MBE related developments are introduced, with which the quality of the nanostructure preparation can be improved.

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.

Abstract: We report on the study on effect of Ga pre-deposition rate on GaAs nanowires grown by self-assisted vapor-liquid-solid (VLS) method. Ga droplets were initially deposited on the surface of Si(111) substrates covered with thin layer of SiO₂. The nanowires were grown by molecular beam epitaxy (MBE). Dependency of structural of nanowires on Ga pre-deposition rate is investigated by Scanning Electron Microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), and X-ray Diffraction Analysis (XRD). The experimental results show that the different in Ga pre-deposition rate significantly affect the surface morphology of samples. Growth rate and the density of nanowires strongly depends on the Ga pre-deposition rate.

Abstract: In this paper, Be-doped GaAs were grown by molecular beam epitaxy (MBE), by changing Be resource temperature, we obtained different doping concentration GaAs samples. The morphologies and electrics properties of the samples were investigated by AFM and Hall measurement. Especially, in low temperature and temperature dependent PL spectra, the Be acceptor related emission were recognized, with the doping concentration increasing, the Be acceptor related emission enhanced too.

Abstract: Si nanowires (NWs) samples have been converted to silicon carbide (SiC) NWs at different conditions of substrate temperature in an ultra-high vacuum using a molecular beam epitaxy (MBE) set-up. Auger electron spectroscopy (AES) and reflection high-energy electron diffraction (RHEED) have been in-situ carried out to control the growth process. Scanning electron microscopy (SEM) and conventional transmission electron microscopy (CTEM) have been used to characterize the resulting nanostructures. In addition, the samples have been prepared by focused ion beam (FIB) in order to have electron-transparently lamellas for TEM with the interface nanowire-substrate. SiC/Si shell/core NWs free of planar defects have been obtained for conversion tmpratures lower than 800oC.

Abstract: ZnO with ZnO/ZnMgO super lattice buffer layers grown by molecular beam epitaxy on Si (100) substrates at room temperature were studied by reversing the epitaxial sequence of ZnO or ZnMgO in the super lattice buffer layers, tuning the oxygen power and the vacuum pressure. The crystal quality was improved by supper lattice buffer layers started with ZnO, using higher oxygen power, and proper vacuum pressure in the growth chamber.

Abstract: C(4×4) reconstruction on arsenic-rich GaAs(001) surface after phase transition has been investigated from the experiment and simulation. We found that the c(4×4) As-rich reconstruction structure of the GaAs (001) surface can be best depicted with the model which there are three As-As dimers without Ga-As dimers in a reconstructed unit cell, and these dimers are found to be aligned perpendicular to the As dimers on β2(2×4) surface.

Abstract: The GaAsP crystal material grown on GaAs substrate has been extensive applications in the area of photoelectronic device. There because GaAsP have advantageous photoelectronic performance and adjustable band gap. We report growth of GaAs1-xPx grown on GaAs substrate by solid source molecular beam epitaxy (SSMBE). On the basis of the optimized Ⅴ/Ⅲ flux ratio, appropriate growth rate, and the substrate temperature for sample growth, different composition GaAs1-xPx layers had been grown on GaAs top. Lattice-mismatched became the big challenges to high-quality epitaxial growth of the GaAs1-x Px materials on GaAs substrate. The crystalline quality, surface morphology were performed by applying high resolution X-ray diffractometry (HRXRD) and high resolution optical microscopy. The etched region and internal defect were also investigated.