The local environment of Co in B5CHx

Abstract

Cobalt-doped boron carbides produced by simultaneous plasma-enhanced chemical vapor deposition of carborane and cobaltocene are investigated. Cobalt does not dope plasma-enhanced chemical vapor deposition grown boron carbides as a random fragment of the cobaltocene source gas. The Co atoms are fivefold boron coordinated ͑R = 2.1 Å͒ and chemically bonded to the icosahedral cages of B 10 CH x or B 9 C 2 H y . Pairwise Co doping occurs with the cobalt atoms favoring sites about 5.3 Å apart. The cobalt strongly hybridizes with the molecular orbitals of the icosahedral cage, and the states in the region of the band gap probably have a strong cobalt weight.

3d transition metal doping of semiconducting boron carbides

“…Monochromatic light was obtained by using a double crystal monochromator of Lemonnier type [18], equipped with Ge(220) crystal pair and the overall resolution was ~ 2 eV. The EXAFS and XANES spectra were collected in the fluorescent yield mode, as has proven to be successful in characterizing other doped boron carbides [6,19,20].…”

The local structure of transition metal doped semiconducting boron carbides

“…The local structure of the cobalt doped semiconducting boron carbide has been determined by extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) spectroscopies [22,26] and to some extent in model cluster calculations [27]. Application of XANES and EXAFS techniques to determine the local structure of the undoped boron carbides has not been successful likely due to the low boron and carbon K-shell x-ray cross-sections [28,29], although the extended electron energy loss fine structure has proved to be a comparatively useful technique [30].…”

Magnetism of Cr-doped diamond-like carbon

“…Relatively extended orbitals of this type occur in some oxides 16 and Co-doped semiconducting boron carbides. [7][8][9] To gauge the usefulness of the present material for spinelectronics applications, we have fabricated Cr-DLC heterojunctions with silicon. We consider chromium a p-type dopant of diamond-like materials, which is supported by our ability to make good heterojunction diodes with n-type silicon.…”

“…15 In these structures, which are of interest in optics and spin electronics, the carbon 2p electrons play a role similar to oxygen 2p electrons in oxides 16 and to boron 2p electrons in Co-doped boron carbide. [7][8][9] Our focus is on Cr-doped hydrogenated diamondlike carbon ͑Cr-DLC͒ and chromium carbide hydrogenated DLC alloys, which we investigate as a mixed matrix material and in the form of heterojunctions for spin-electronics applications. Previous research on similar system indicates that clustering of chromium impurities is expected for concentrations exceeding about 1.5%, 17 although Fan et al 18 reported uniform Cr distribution in C matrix at lower levels ͑about 6 at.…”

“…[1][2][3][4] This includes dilute oxides, 5,6 where the dopants form a solid solution in the host lattice, weakly clustered impurities as in Codoped semiconducting boron carbides, [7][8][9] and clusterforming dopants such as cobalt in some oxide dielectrics. [10][11][12][13][14] Less effort has been devoted to wide bandgap materials such as diamond, where the dielectric response is somewhat enhanced but the effective mass is comparatively large.…”