This work presents an experimental study on the dislocation luminescence in GaN by nanoindentation, cathodoluminescence, and Raman. The dislocation luminescence peaking at 3.12 eV exhibits a series of special properties in the cathodoluminescence measurements, and it completely disappears after annealing at 500°C. Raman spectroscopy shows evidence for existence of vacancies in the indented region. A comprehensive investigation encompassing cathodoluminescence, Raman, and annealing experiments allow the assignment of dislocation luminescence to conduction-band-acceptor transition involving Ga vacancies. The nanoscale plasticity of GaN can be better understood by considering the dislocation luminescence mechanism.
A method to grow gallium nitride (GaN) films directly on the graphene layers by hydride vapor phase epitaxy (HVPE) method is reported in this work. We used a chemical vapor deposition (CVD) method to grow graphene on a copper foil, and the test results showed the presence of monolayer graphene at most regions. GaN films were grown on the graphene/MO-GaN substrate (GaN which was grown by metal organic vapor phase deposition) and MO-GaN template by HVPE method. Raman Spectroscopy, Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD) were adopted for characterization. By comparing with the MO-GaN substrate, the crystalline quality of the GaN films were both increased. However, the crystalline quality of the HVPE-GaN with graphene interlayer is slightly lower than that directly grown on MO-GaN.
With the use of Visual C++ 6.0 programming development tools as the secondary development of Unigraphics NX (UG), dynamic link library DLL plug-ins were created. This paper takes fixed pedestal which is a standard part with assembly level of mold as an example, describing the parametric assembly modeling technology and implementation method of automatic virtual assembly process. The method can improve the design efficiency greatly by changing the related parameters of the parts to regenerate model fast and complete the design as well as assemble of fixed pedestal. It is proved that this method can meet the mould design requirements, and can be expanded and used for parameterized modeling and assembling of other standard parts with assembly level of mold in the practice.
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