Formation of hydrogen-boron complexes in boron-doped silicon treated with a high concentration of hydrogen atoms

The formation of hydrogen (H) related complexes and their effect on boron (B) dopant were investigated in B-ion implanted and annealed silicon (Si) substrates treated with a high concentration of H. Isotope shifts by replacement of 10B with 11B were observed for some H-related Raman peaks, but not for other peaks. This shows proof of the formation of B-H complexes in which H directly bonds to B in Si. This is an experimental result concerning the formation of B-H complexes with H bonded primarily to B. Electrical resistivity measurements showed that the B acceptors are passivated via the formation of the observed B-H complexes, as well as the well-known passivation center in B-doped Si; namely, the H-B passivation center

DC AND AC ELECTRICAL PROPERTIES OF PTC BARIUM TITANATE CERAMICS

Les propriétés électriques en courant continu et alternatif des thermistances CTP ont été étudiées dans l'intervalle de température (30-450°C). Le modéle de Heywang seul ne permet pas une interprétation quantitative des résultats. Il est nécessaire de prendre en compte l'hétérogénéité du systéme.The dc and ac electrical properties of PTC barium titanate ceramics were measured in the temperature range from 30 to 450°C. The Heywang's model alone is not sufficient to perform a quantitative analysis of the results. The heterogeneity of the system is taken into account

STRUCTURAL CHARACTERIZATION OF EPITAXIAL BATIO3 THIN-FILMS GROWN BY SPUTTER-DEPOSITION ON MGO(100)

Epitaxial thin films of BaTiO3 have been prepared using radio-frequency magnetron sputter deposition on MgO(100) substrates. Various x-ray-diffraction techniques were employed to characterize the crystal structure of the films. The films were fully tetragonal and consisted of c domains. Their tetragonality has been shown to be 1.013, which is almost the same as the bulk value of BaTiO3. However, the cross-sectional transmission electron microscopic micrograph showed that a very small amount of a domains coexists forming 90 degrees domain boundaries in the matrix of c domains. In spite of the negligible strain caused by the phase transformation, it seems to be inevitable to form a certain small amount of a domains in the BaTiO3 film on MgO system. (C) 1995 American Institute of Physics.open1157sciescopu

√3 linear structures in the Te/Ni(111) system

Surface structures in the Te/Ni(111) system are revealed by using reflection high-energy electron diffraction combined with X-ray and ultraviolet photoelectron spectroscopies. At a 0.33 mono-layer (ML)-Te/Ni(111) surface, a reversible structural phase transition is observed with a transition temperature Tc of 380 $^{\circ}$C. The diffraction pattern from the low temperature phase is accompanied by streaks. The high and low temperature phases are characterized by $\sqrt{3} \times \sqrt{3} R\pm30^{\circ}$ and $3 \times \sqrt{3}$ rectangle, respectively. The mechanism of the phase transition is explained by the order-disorder transition with a rumpled chain model. Both 0.51 ML- and 0.44 ML-Te/Ni(111) surfaces exhibit the complex diffraction patterns accompanied by diffuse streaks. These surface structures are characterized by the $7 \times \sqrt{3}$ rectangle and $5 \sqrt{3} \times \sqrt{3} R \pm30^{\circ}$, respectively. All diffuse streaks obtained at the above surfaces are consistently interpreted in the view of the ill-ordered arrangements of the well-ordered $\sqrt{3}$ linear chains. It is shown that the “$\sqrt{3}$ linear structure” is the key in the Te/Ni(111) system

Graphitization of ultrathin amorphous carbon films on Si(001) by Ar+ ion irradiation at ambient temperature

We report the graphitization of ultrathin (8 nm) amorphous carbon films on Si(001) by 2 MeV Ar+ ion irradiation at ambient temperature. The resulting graphite films show the preferred orientation in the film normal direction, but random distribution in the film plane direction. The smooth surface and interface suggest that the activation energy for the graphitization is supplied mostly by the electronic stopping process while Ar+ ions travel through the amorphous carbon film. (C) 2000 American Institute of Physics. [S0021-8979(00)06513-0].open1110sciescopu

SCANNING AUGER MICROPROBE INVESTIGATION OF GRAIN BOUNDARY SEGREGATION IN SOME ELECTROCERAMICS

Spatial distributions of elements near the grain boundaries of both ZnO varistors and NiO ceramics were investigated by a scanning Auger microprobe. In ZnO varistors doped with Bi and Co, the content of the additive Bi segregated at every grain boundaries measured in the range from 2 to 10 nm in thickness. In many segregation layers, a total molar fraction of cations, Zn and Bi, was higher than that of oxygen, suggesting that the segregated Bi was in a state with a deficit of oxygen. In NiO ceramics doped with Li, the content of the additive Li segregated at grain boundaries in the range from 10 to 20 nm in thickness. In this material, contrary to the cases of the varistor, the segregated Li was in a state with a surplus of oxygen

Visible-light-driven photocatalysis on fluorine-doped TiO2 powders by the creation of surface oxygen vacancies

F-doped TiO2 (FT) powders were prepared by spray pyrolysis from an aqueous solution of H2TiF6. These FT powders demonstrated very high visible-light (Vis) photocatalytic activities for decompositions of both acetaldehyde and trichloroethylene, although their UV–Vis spectra indicated that F-doping had less effect on the optical absorption property of bulk TiO2. However, photoluminescence (PL) spectra revealed that two kinds of oxygen vacancies (F and F+ centers) were formed by F-doping. The appearance of Vis photocatalytic activity for FT powders was ascribed to the creation of these oxygen vacancie