Electronic structures ofB2pandC2plevels in boron-doped diamond films studied using soft x-ray absor

Abstract

X-ray absorption (XAS) and emission (XES) spectroscopy near B K and C K edges have been performed on metallic (ϳ0.1 at. % B, B-diamond) and semiconducting (ϳ0.03 at. % B and N, BN-diamond) doped diamond films. Both B K XAS and XES spectra show a metallic partial density of states (PDOS) with the Fermi energy of 185.3 eV, and there is no apparent boron-concentration dependence in contrast to the different electric property. In C K XAS spectrum of B-diamond, the impurity state ascribed to boron is clearly observed near the Fermi level. The Fermi energy is found to be almost same with the top of the valence band of nondoped diamond: E V = 283.9 eV. C K XAS of BN-diamond shows both the B-induced shallow level and N-induced deep and broad levels as the in-gap states, in which the shallow level is in good agreement with the activation energy ͑E a = 0.37 eV͒ estimated from the temperature dependence of the conductivity; namely, the change in C 2p PDOS of impurity-induced metallization is directly observed. The electric property of this diamond is ascribed mainly to the electronic structure of C 2p near the Fermi level. The observed XES spectra are compared with the discrete variational X␣ (DVX␣) cluster calculation. The DVX␣ result supports the strong hybridization between B 2p and C 2p observed in XAS and XES spectra, and suggests that the small amount of boron ͑ഛ0.1 at. % ͒ in diamond occupies the substitutional site rather than interstitial site.

Boron spectral density and disorder broadening in B-doped diamond

“…To summarize: the weights of the DOSs are arranged in the order of B, nn C, second neighbor (2nd n) C, and bulk C, in order of increasing binding energy. [24] This trend is consistent with the interpretation of x-ray absorption and emission spectroscopy by Nakamura et al [25,26] The B DOS is very similar to that of the nn C. Note the sharp peaks confined to B and the nn C atom between −2 eV and −1 eV, arising from strong B 2p character on the plane of kz = π/a. For C atoms progressively further from the B atom, the peak at −11 eV becomes sharper.…”

Superconductivity in carrier-doped silicon carbide

“…Many experimental and theoretical studies have focused on the origin of the metallic nature responsible for superconductivity in diamond. Investigations continue to clarify whether it originates from the holes at the top of the diamond valence band or from the boron impurity band formed above the valence band [5][6][7][8][9][10][11][12][13][14][15]. In particular, a higher-T c superconductivity in C:B has been suggested from a theoretical model by a Japanese group [16][17][18], where bonds transform into bands by carrier doping of a semiconductor.…”

Optical properties of boron-doped diamond

“…At higher boron concentration, as the average distance between boron atoms is close to the acceptor Bohr radius, the metallic conduction appears, with the room temperature conductivities of a few 10 2 Ω −1 cm −1 . [5,6,7] The superconductivity of boron doped diamond at several Kelvins is now the most interesting phenomenon. [8,9] In order to understand the origin of this phenomenon, a number of first-principle calculations have been performed recently with regard to the electronic structure, lattice dynamics, and the electron-phonon coupling of * Corresponding author; Electronic address: nlwang@aphy.iphy.ac.cn the doped system.…”

“…We noticed that the peak energy corresponds well to the boron acceptor levels locating at 0.38 eV from the top of valence band as determined from many other experimental probes. [7,17] So, it just corresponds to the interband transition from the top of the valence band to the impurity states.…”