High homogeneity heavily MgO-doped lithium niobate (MgLN for short) single crystals were grown by Czochralski method. The as-grown crystals were poled at high temperature, so as to obtain single ferroelectric domain structure. UV absorption edge, OH absorption peak, optical homogeneity of the crystal were tested, respectively. Micro- compositions along the radial direction were analyzed by EDS method and “line scan” of the distribution of Mg element along the radial direction was investigated by WDS method. The results showed that high homogeneity MgLN crystals were obtained with proper starting composition and improved growth process of Czochralski technology. UV absorption edge at 308 nm and OH absorption peak at 2828 nm were observed. The optical homogeneity Δn<5.11×10-5. Finally, ferroelectric domain structure was observed by optical microscope by chemical etching method. High uniformity single ferroelectric domain structure was obtained by applying an external electric field at 1200¡æ
Gas etching and homoepitaxial growth on a nominally on-axis 2-inch 6H-SiC (0001) Si-face were studied. Regular steps with one unit cell height and complex pattern with facets and steps were observed after gas etching in the central region and edge region, respectively. The homoepitaxial growth shows that the complex (facets & steps) pattern expands and merges during the growth to bring on a rough epi-layer surface in the edge region. The steps with one unit cell height on the substrate split into steps with bilayers on the epilayer. The different lateral growth rates of <11-20>- and <1-100>-orientated steps make the width of steps orientated to <11-20> much larger than the ones orientated to <1-100>.
Hexagonal aluminium nitride (AlN) microrods with high crystalline quality were grown by physical vapor transport (PVT) method at low growth temperature between 1700 and 1850℃. The length of as-grown microrod is around 1 cm, and the width between 200-400 μm. The microrod exhibits typical hexagonal geometrical shape with pale yellow color under optical microscopy. Scanning electron microscope (SEM) and atomic force microscope (AFM) images show each microrod with closely arranged step waviness, of which the step interval is 2-4 μm and the height several nanometers. Raman spectrum characterization showed characteristic peaks of high crystalline AlN. The rod-like structure is attributed to slow growth velocity at lower crystalline temperature, enabling Al and N atoms having enough time to move to the lower energy site and to form hexagonal microrod along <0001> direction. High quality hexagonal AlN microrod is an enrichment to one-dimensional semiconductor materials. Data from this study suggest that, by further study on size and impurity control, high performance miniaturized opto-electronic device is hopeful to be achieved.
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