特別講演会 National Tsing Hua University Michael H. Huang
|特別講演会 National Tsing Hua University Michael H. Huang
“Strongly Facet-Dependent Properties of Semiconductor Crystals”
National Tsing Hua University Michael H. Huang
Our extensive investigations on the various properties of Cu2O, Ag2O, PbS, and Ag3PO4 crystals have shown they possess facet-dependent photocatalytic activity, electrical conductivity, and optical properties. For electrical conductivity properties, a Cu2O octahedron is highly conductive like a metal, a cube behaves like a semiconductor, while a rhombic dodecahedron is an insulator. Recently, we have shown Si and Ge wafers also possess facet-dependent electrical conductivity behaviors. We have also synthesized size-tunable Cu2O cubes, octahedra, and rhombic dodecahedra to demonstrate their possession of size- and facet-dependent light absorption and emission properties This means band diagram of semiconductors must be modified to account for size and facet effects. All these properties are related. Bond length, bond geometry, and frontier orbital electron distributions within in the ultrathin Si and Ge surface layers are different from those of the bulk, showing semiconductor facet effects should have quantum mechanical basis at the orbital level.