Present knowledge of electronic properties and charge transport of icosahedral boron-rich solids

摘要: B12 icosahedra or related structure elements determine the different modifications of elementary boron and numerous boron-rich compounds from α-rhombohedral with 12 to YB66 type about 1584 atoms per unit cell. Typical are well-defined high density intrinsic defects: Jahn-Teller distorted icosahedra, vacancies, incomplete occupancies, statistical occupancies antisite defects. The correlation between point defects electron deficiencies solves discrepancy theoretically predicted metal experimentally proved semiconducting character. generate split-off valence states, which decisive for electronic transport, a superposition band-type hopping-type conduction. Their share depends on actual conditions like temperature pre-excitation. theoretical model bipolaron hopping is incompatible experiments. Technical application typically p-type icosahedral solids requires suitable n-type counterparts; doping other possibilities discussed.