Bi-doped Samples Research Articles

Electrical resistivity of bismuth implanted into silicon

We investigate the electrical properties of Bi-doped Si samples, prepared by ion implantation, in a range of concentrations around and above the metal–nonmetal transition. Comparison between experimental and theoretical values of the resistivity brought out that in these samples a similar behavior is observed as for other n-doped Si, thus confirming the results obtained in the same range of impurity concentration, i.e., ρ(Sb)≤ρ(P)≤ρ(As)≤ρ(Bi).

Ｌａ２−ｘＢｉｘＣｕＯ４の合成と超伝導

La2-xBixCuO4+z (0<x<0.2) was prepared under oxygen pressures between 1bar and 0.5kbar. The solid solution La2-xBixCuO4+z showed superconductivity only after being annealed under high oxygen pressure. For La2CuO4+z the superconducting transition temperature, Tc, was almost independent of z at around 40K, while the Tc of Bi-doped samples showed a strong dependence. The superconductive volume fraction was considersbly increased by the Bi doping. The known phase separation into nearly stoichiometric La2CuO4 and superconducting La2CuO4+z seems to be suppressed by the Bi-for-La substitution.

Structural and transport properties of the triple-layer compounds Ba 4(Pb 1−xBi x) 3O 10 (0≤ x

A series of new compounds Ba 4(Pb 1−xBi x) 3O 10 with 0≤x<0.3 has been prepared and characterized by X-ray and electron diffraction. The d.c. resistivity vs. temperature data for different x values are presented and structural features are compared to those of the superconducting phase Ba(Pb 1−xBi x)O 3. The “mother-compound” Ba 4Pb 3O 10 is tetragonal, with lattice constants a=0.4280(1) and c=3.017(1) nm. Its structure can be regarded as a stacking of Ba(PbBi)O 3 triple-layers, separated by single BaO layers. Electron diffraction reveals the presence of a weak superstructure with the a-axis related to that of the perovskite by a=√2a p. Frequent intergrowth of this phase with the perovskite structure is observed. The conductivity of the samples Ba 4Pb 3O 10 is nearly independent of temperature, while Bi-doped samples exhibit semiconductor-like behaviour at low temperature. No superconducting transition is observed down to 2K.

Electrical properties of bismuth-doped non-stoichiometric strontium titanate ceramics

Pure and Bi-doped samples of SrTiO 3 with Sr/Ti ratios ranging from 0.980 to 1.010 were sintered in air at 1500 °C. Grain growth was promoted in the non-stoichiometric bismuth-doped compositions. Unlike the non-doped samples which were ohmic insulators, bismuth-containing specimens showed non-ohmic behaviour, with non-linear coefficients depending on stoichiometry. The dependence of resistivity on temperature and capacitance-voltage analysis were used to correlate the electrical characteristics with accepted models.

High resolution study of the group V impurities absorption in silicon

Abstract High resolution spectra of P-, As- and Sb-doped Si have allowed the determination of the “natural” width of the impurity lines for concentration in the range of 1014 at cm−3 and below. The width of the P-lines makes possible the observation of the 5p0 line, very close to the 4p± line. In the Sb- and As-doped samples, an effect similar to concentration broadening is observed. Results on P- and Bi-doped samples at lower resolution give evidence of the observation of the 3d0(P) line and of internal Stark effect in the Bi-doped sample.