Papers by Keyword: VLS

Abstract: As the physical and electrical properties of silicon nanowires (SiNWs) are determined by their dimension, it is necessary to control their dimension to integrate them in a device. SiNWs were synthesized via Vapor-Liquid-Solid (VLS) mechanism in hot-wire chemical vapor process (HWCVP) technique using silane as a Si source and Sn as a catalyst. Different sizes of nano-template have been made by depositing of different amount of Sn using thermal evaporation method. The size of nano-template is found to be increased with the quantity of Sn. The diameter of resulted SiNWs depends on the size of the nano-template and it increases with the nano-template size. However, the diameter of SiNWs is found to be much larger than the used nano-template which is due to the deposition of silicon film on the sidewalls of the growing SiNWs. It is demonstrated here that the diameter of the interior core of SiNWs can be controlled desirable by adjusting the size of the nano-template.

Abstract: Structural control and morphological modification of a series of Si-based nanostructures were studied from the viewpoint of modifying the catalyst’s characteristics. The catalyst was modified from a liquid to a solid during its growth. The growth evolution of the faceted Si nanowires occurred via a vapor–liquid–solid mechanism followed by a silicide vapor–solid–solid mechanism. The shapes of the catalysts defined the shapes of the nanowires during the vapor–solid–solid growth. The catalyst was further modified by the deposition of MnCl2. Only irregularly shaped Si particles or MnCl2 particles were observed on top of the Si nanowires. The characteristic modification of catalysts by liquid-phase crystal nucleation and deposition of liquid-phase droplets was discussed. In addition, the synthesis of a CrSi2 nanowire bundle by the formation of dense nanoparticles was studied.

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: This work deals with the selective heteroepitaxial growth of silicon carbide on (100) diamond substrates using the Vapour-Liquid-Solid (VLS) transport. The morphology, the structure and doping were determined using various characterization techniques. In order to achieve succesful heteroepitaxy, the diamond surface was silicided by solid-state reaction between a silicon layer and the substrate at 1350 °C. This allowed forming a SiC buffer layer on which p-doped 3C-SiC(100) islands elongated in the <110> directions were obtained after VLS growth. The influence of the experimental parameters on the epitaxial growth is discussed.

Abstract: By analyzing the shipboard missile vertical launching system (VLS), we simplified the assembly model and reconstructed it with mathematical methods, established the clearance parameter and deviation angle mathematical formulas. In considering of the assembly errors of guide rail in missile vertical launcher system, we studied assembly clearance parameters effects on the system at first. And then established dynamic simulation model, researched the relationship between assembly clearance parameters and missile launching status. At last, used the above relationship model and conclusions, developed a prototype simulation method, and provided the foundation and guidance for design of missile vertical launching system.

Abstract: As one-dimensional GaN material has excellent physical properties, it owns a huge prospect in the field of optoelectronic devices, and nanowire is currently one of the hotspots, at home and abroad, which had already invested a considerable force into the GaN nanowires. This paper studied the growth method based on Gas Liquid Solid (VLS) mechanism using Ni as catalyst in a chemical vapor deposition (CVD) system. By scanning electron microscopy (SEM), energy dispersive X-ray fluorescence (EDX) spectroscopy, transmission electron microscopy (TEM) test, we focused on the influence of temperature and pretreat on the morphology and properties of GaN nanowires. At the same time, we explored the law and gave an appropriate explanation.

Abstract: Undoped and B-doped silicon-based nanowires (SiNWs) were synthesized by vapor-liquid-solid growth, and SiNW devices using Au electrodes were prototyped using focused ion beam (FIB) processing. Needle-shaped thin SiNWs were formed at a substrate temperature between 1170 and 1313 °C. The average and minimum diameters of the B-doped SiNWs were 72 nm and 52 nm, respectively. According to the current-voltage characteristics, SiNW devices have ohmic properties, and the estimated resistivity of the undoped and B-doped SiNWs are about 3.8 × 10³ Ωcm and 1.7 × 10³ Ωcm, respectively.

Abstract: Abstract. In this paper, conditions for obtaining high growth rate during epitaxial growth of SiC by vapor-liquid-solid mechanism are investigated. The alloys studied were Ge-Si, Al-Si and Al-Ge-Si with various compositions. Temperature was varied between 1100 and 1300°C and the carbon precursor was either propane or methane. The variation of layers thickness was studied at low and high precursor partial pressure. It was found that growth rates obtained with both methane and propane are rather similar at low precursor partial pressures. However, when using Ge based melts, the use of high propane flux leads to the formation of a SiC crust on top of the liquid, which limits the growth by VLS. But when methane is used, even at extremely high flux (up to 100 sccm), no crust could be detected on top of the liquid while the deposit thickness was still rather small (between 1.12 μm and 1.30 μm). When using Al-Si alloys, no crust was also observed under 100 sccm methane but the thickness was as high as 11.5 µm after 30 min growth. It is proposed that the upper limitation of VLS growth rate depends mainly on C solubility of the liquid phase.

Abstract: This paper deals with electrical characterization of PiN diodes fabricated on an 8° off-axis 4H-SiC with a p⁺⁺ localized epitaxial area grown by Vapour-Liquid-Solid (VLS) transport. It provides for the first time evidence that a high quality p-n junction can be achieved by using this technique followed by a High Temperature Annealing (HTA) process.

Abstract: Silicon-based nanowires (Si-NWs) were fabricated by vapor liquid solid (VLS) growth, and Si-NW device was prototyped using focused ion beam (FIB) processing. The needle shaped thin Si-NWs were formed at a substrate temperature between 1120 and 1313°C. The average and minimum diameters of the NWs were confirmed 60 nm and 44 nm, respectively. As the double-layered structure was observed in the NWs by transmission electron microscope images, it is possible that those are silicon-based NWs with Si core and SiO₂ shell structure. From current-voltage characteristics, the Si-NW device has a semiconducting property, and the estimated resistivity of the Si-NW is about 3.1 x 10⁴ Ωcm.