INTERRELATIONS OF ATOMIC STRUCTURES, ELECTRONIC-STRUCTURES, ELECTRON-TRANSPORT, AND MAGNETIC-PROPERTIES ACROSS THE METAL-INSULATOR-TRANSITION FOR AMORPHOUS VXSI100-X -LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-74) ALLOYS

The interrelations of the atomic structures, electronic structures, el ectron transport, and magnetic properties for the amorphous VxSi100-x alloy system have been studied over a wide composition range, 7 less t han or equal to x less than or equal to 74, with particular attention paid to their changes across the metal-insulator transition. By analys ing the temperature dependence of the conductivity, we concluded that the metal-insulator transition occurs in the composition range 15 < x < 20. Structural studies revealed that the V atom is substituted for t he Si atom in the tetrahedrally bonded Si network in the range where x < 10, whereas the local atomic structure resembles that of the VSi2 i ntermetallic compound in the range 20 < x < 40. These two local struct ures are apparently competing with each other in the critical composit ion range 10 < x < 20. Both XPS valence band spectra and electronic sp ecific heat measurements proved that the density of states at the Ferm i level is definitely finite even in the insulating regime, i.e., for x < 15. Both V L alpha and Si K beta SXS measurements showed that the V 3d states appear just below the Fermi level, and hybridize with the Si 3p states. It is also found that the V atom in the insulating regim e possesses a localized magnetic moment, and that the magnetic suscept ibility gives rise to a Curie-Weiss-like temperature dependence at low temperatures. Finally, the uniqueness of the electron transport prope rties for the amorphous VxSi100-x alloys is emphasized by the rho-gamm a diagram, in which the metal-insulator transition is shown to occur w hile the density of states at the Fermi level remains finite.