The single crystal growth of boron phosphide (BP) by employing the high pressure flux method and chemical vapor deposition (CVD) process is described together with characterization of the prepared BP and its electrical, thermal, semiconducting, and electrochemical properties. BP single crystals prepared by the high pressure flux method contain copper used as the flux, but they are promising for photocathode materials. BP single crystalline wafers prepared by the CVD process using Si wafer substrate contained autodoped silicon with the concentration of 1018−1020 atoms·cm−3, depending on the growth temperature and the substrate plane. The Si atoms which act as acceptors are incorporated at phosphorus sites in BP. The lattice constants determined by the Bond method explain the conduction type of BP. Some electronic transport properties such as donor and acceptor levels and lattice scattering process before and after thermal neutron experiments are clarified. The thermal conduction is limited by three-phonon processes. The formation of defects by thermal neutron irradiation and that of structural disorder by ion-irradiation are mentioned. Schottky diodes consisting of n–BP and Sb or n–BP and Au, which are denoted as n–BP–Sb and –Au, respectively, show excellent characteristics, and their barrier heights are independent of metals and two-thirds of energy bandgap, expected from the surface-state model. Finally, recent results on thermoelectric properties of sintered specimens are mentioned.
Amorphous boron carbide (a-B1−xCx) is believed to have an icosahedron-based random network. In this paper, vibrational properties of a-B1−xCx films are studied by IR and Raman spectra, placing particular emphasis on the interpretation of the most prominent 1100-cm−1 band associated with the B–C bond. The 1100-cm−1 band appears in both IR and Raman spectra, and the frequency variation and the intensity as a function of the C content are examined, together with evaluation of the absolute absorption coefficients. Within the framework of the impurity-induced vibration theory, the 1100-cm−1 band is characterized. The estimation of the force constants by the observed frequencies leads to a conclusion that the vibration can be classified as an extrinsic and preferably a local mode. This vibration is well described as the stretching mode of a localized two-center bond between the B and C atoms. In this sense, the C atom in amorphous B1−xCx is not regarded as a network constituent. The frequency shift with the C content supports this conclusion. The absorption intensity of this band exhibits large values for the transverse effective charge of a-B1−xCx. A numeric estimation shows that most part of the observed transverse effective charge comes from the localized charges of the C impurity. This mechanism of the effective charge is consistent with the above argument of frequency. The intrinsic vibrations of the amorphous boron network based on the icosahedron structure reside over the range from 400 to 1000 cm−1 with a small peak at 800 cm−1.
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