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Directing the morphological evolution of one-dimensional materials in order to tune their properties for a variety of practical applications in optical sensing and solar cells is an ongoing effort. Here, we establish a systematic method for exerting control over the morphology of nanowires (NWs) grown via a vapour–solid–solid (VSS) process from different metal catalysts. We use germanium, a technologically important material, to demonstrate how catalysts influence the axial growth rate of a crystalline core against the lateral vapour deposition of an amorphous shell which in turn deforms the NWs into straight, tapered or spiral geometries due to interfacial stress. Finite element method (FEM) and molecular dynamic (MD) simulations are further utilized to confirm the proposed mechanism of deformation in crystalline–amorphous core–shell NWs.

Solid state thermal diffusion is not a common method of impurity doping in silicon carbide (SiC) device fabrication due to the extremely high temperatures required for such a process to occur. We have recently reported that solid state impurity doping by thermal diffusion in SiC is possible if there is a parallel mechanism, such as oxidation or silicidation that creates silicon or carbon vacancies, which then allows dopant impurities to diffuse into these vacancies. This paper describes the experimental procedures by which oxidation and silicidation can be used to generate vacancies and enhance impurity doping at temperatures below 1400 oC‎

The low temperature diffusion of Boron in bulk SiC crystals is investigated and simplified model of such diffusion is presented. The method of UV stimulated etching by aqueous solution of KOH is proposed and some experimental data on influence of defects on quality of prepared p-n junctions are presented.

We have performed a combined investigation of experiment and theory on the infrared reflectance from cubic SiC grown on Si by chemical vapor deposition. A damping behavior of the interference fringes away from the reststrahlen band and a dip or notch within the “flat top” are observed from some samples while they does not occur in high quality 3C-SiC/Si samples. The former is interpreted due to an interfacial transition layer existed between SiC-Si and a rough surface, while the latter can be demonstrated by a three-component effective medium model.

The crystal quality of a 4H-silicon carbide (4H-SiC) epitaxial layer is crucial to the development of high-performance 4H-SiC-based electronic power devices. However, the quality assessment of 4H-SiC homoepitaxial thin film is problematic because the same bulk material interferes with the probe of the epilayer. In this paper, we propose a simple and straightforward strategy to assess the quality of a homoepilayer using ultraviolet (UV) Raman spectroscopy (RS). Rather than focusing on the normally allowed modes, we shift our attention to the forbidden modes instead. We demonstrate that forbidden modes, which were usually ignored, are more sensitive to the crystalline imperfection and can be an effective quality probe. Our approach analyzes the crystal quality swiftly, without the need for the data fitting involved in the conventional method, and therefore makes the quality assessment much more efficient. The new method may also be applied to the other thin film materials.

Synchrotron radiation X-ray absorption and UV 325 nm excitation Raman scattering- photoluminescence (PL) have been employed to investigate a series of 4H-SiC wafers, including bulk, epitaxial single or multiple layer structures by chemical vapor deposition. Significant results on the atomic bonding and PL-Raman properties are obtained from these comparative studies.

Photoluminescence (PL), Fourier-transform infrared (FTIR), and deep-level transient spectroscopy (DLTS) measurements have been made on various samples of silicon-doped liquid-encapsulated Czochralski-grown GaAs. All the samples show prominent PL peaks at 1.443 and 1.325 eV together with their longitudinal optic (LO) phonon peaks. The PL peak at 1.443 eV has been reported in the literature as being due to either GaAs or a boron-related defect. The FTIR results show the presence of BGa at 540.3 and 517.0 cm−1 and SiGa at 383.6 cm−1. We have observed that there is no correlation between the PL peak at 1.443 eV and BGa. Thus, we believe that this PL peak is related to the GaAs antisite defect. The presence of EL2 in the samples has been measured using DLTS. We have found that the intensity of the PL peak at 1.443 eV varies inversely with that of the EL2 peak. This relationship indirectly confirms that the 1.443 eV peak is due to the gallium antisite defect. The PL peak at 1.325 eV is significantly different from those reported in the literature for GaAs:Si. Measurements have also been made on samples of GaAs:Si annealed under different arsenic overpressures.

Transient photocurrent decay experiments were carried out to study the effects of internal potential barriers, which could be due to filled traps and metallic inclusions, on the detrapping process in semiconductors. Experiments were carried out with single crystals of Cu2O, annealed in various ways, because of the ease in inducing large defects in this material. It was found that samples of Cu2O with different defect structures had different values of trapping parameters. These different values are explained in terms of barrier formation at the trapping centres. For those samples of Cu2O that contain copper precipitates, the presence of asymmetrical barriers is proposed in order to explain the difference in the trapping parameters when compared with the standard type of Cu2O.The field dependent behaviour of the detrapping time in samples of Cu2O that do not contain copper precipitates could be explained by the presence of both the Poole–Frenkel effect and the photo-impact ionization of the traps. Those samples that contain copper precipitates do not show any field dependent behaviour of the detrapping process, probably owing to the formation of internal space charge regions.