Structural- and electronic-property investigations on metal-doped beta-rhombohedral boron

Here we investigate on the possibility of metal transition upon V and Ni doping into beta-rhombohedral boron (beta-rh. B). For V-doped beta-rh. B, DC conductivity sigma and Pauli paramagnetic shift chi(0) monotonously increase with increasing V concentration, suggesting that metal transition may occur by further V doping. Interestingly enough, however, at the highest Ni concentration (Ni4.5B105 phase), sigma and chi(0) decrease again, such that Ni-doped beta-rh. B reverts back to an insulator. For these properties, filling of intrinsic acceptor states comprised of B-12 icosahedral clusters and possibility of metal transitions of beta-rh. B is discussed.