No abstract

PACS 81.05. Ea, 81.15.Hi Application of migration-enhanced deposition sequence to area selective growth of GaAs and other III -V compound semiconductors makes it possible to achieve well-defined area selective growth even using solid source molecular beam epitaxy. Successful growth of small disks and other structures has been performed on SiO 2 masked (111)A and (111)B substrates at temperatures around 590 °C. General rule for facets formation suggests that the facet angle is quite sensitive to the V/III flax ratio as well as the substrate orientation. To create vertical {110} facets around the structures at relatively low V/III flux ratios, (111)A substrates is much more preferable to (111)B substrate. However, high density of hillocks emerges on the structures grown on (111)A substrate. It is found that the hillocks are caused by the stacking faults. The density of hillocks has been dramatically reduced by depositing As in the Ga deposition period.

We have carried out area-selective epitaxial growth of GaAs on GaAs(111)A substrates using migration-enhanced epitaxy and have investigated the pyramidal hillocks formed on the grown surface. Scanning electron microscopy and atomic force microscopy observations indicate that these hillocks can be classified into two types: hillocks with small top plateaus and those with large plateaus. Investigations on the growth condition dependence of surface morphology and plan-view transmission electron microscopy observation have revealed that both types of hillocks are caused by stacking faults. Hillock cores are found to be stacking fault tetrahedra, whose formation processes result in two types of hillocks. Additionally, we have succeeded in improving the surface flatness by increasing the surface arsenic pressure during growth.

No abstract

Lithium-ion conducting glass-ceramic electrolyte in the composition 75Li 2 S•5P 2 S 3 •20P 2 S 5 (mol%) was prepared by heat-treatment of an amorphous precursor. The amorphous precursor was obtained by a high-energy ball-milling process. The glass-ceramic showed high ion conductivity 2.0 x 10-3 Scm-1 at room temperature. Raman scattering measurements suggested that the glass-ceramic essentially composed of thio-phosphate anions, PS 4 3and P 2 S 6 4-, as structural units. A laboratory-scale all-solid-state battery was also assembled by use of the glass-ceramic as solid electrolytes and LiNi 1/3 Mn 1/3 Co 1/3 O 2 powders as positive electrode materials. The all-solid-state battery showed good charge-discharge cycle performance at room temperature under a constant current density of 0.1 mAcm-2 .