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

√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

Au-Decorated 1D SnO2 Nanowire/2D WS2 Nanosheet Composite for CO Gas Sensing at Room Temperature in Self-Heating Mode

We have designed a new ternary structure to enhance the sensing properties of WS2 nanosheet (NS)-based gas sensors at room temperature (RT) in self-heating mode. SnO2 nanowires (NWs, 10–30 wt%) were added to WS2 NSs and then Au nanoparticles (NPs) were deposited on the surface of the resulting composites by UV irradiation. The Au-decorated 10 wt% SnO2–WS2 composition showed the highest gas sensing properties. The presence of SnO2 NWs on the WS2 NSs effectively enhanced the diffusion and adsorption of gas species into deeper parts of the gas sensor. Furthermore, the chemical sensitization of Au (increase in oxygen ionosorption; spillover effect and catalytic effect towards CO) contributed to an enhanced response to CO gas. Gas sensing tests performed in the self-heating mode demonstrated the possibility of realizing a low-voltage, low-power-consumption CO gas sensor based on the Au-decorated 10 wt% SnO2–WS2. The sensor response under 60% relative humidity (RH) conditions was 84% of that under dry conditions, which shows that CO sensing is possible in wet environments at room temperature operation

Au-Decorated 1D SnO₂ Nanowire/2D WS₂ Nanosheet Composite for CO Gas Sensing at Room Temperature in Self-Heating Mode

We have designed a new ternary structure to enhance the sensing properties of WS2 nanosheet (NS)-based gas sensors at room temperature (RT) in self-heating mode. SnO2 nanowires (NWs, 10–30 wt%) were added to WS2 NSs and then Au nanoparticles (NPs) were deposited on the surface of the resulting composites by UV irradiation. The Au-decorated 10 wt% SnO2–WS2 composition showed the highest gas sensing properties. The presence of SnO2 NWs on the WS2 NSs effectively enhanced the diffusion and adsorption of gas species into deeper parts of the gas sensor. Furthermore, the chemical sensitization of Au (increase in oxygen ionosorption; spillover effect and catalytic effect towards CO) contributed to an enhanced response to CO gas. Gas sensing tests performed in the self-heating mode demonstrated the possibility of realizing a low-voltage, low-power-consumption CO gas sensor based on the Au-decorated 10 wt% SnO2–WS2. The sensor response under 60% relative humidity (RH) conditions was 84% of that under dry conditions, which shows that CO sensing is possible in wet environments at room temperature operation

Ultrafast Dynamics of Surface-Enhanced Raman Scattering Due to Au Nanostructures

Ultrafast dynamics of surface-enhanced Raman scattering (SERS) was investigated at cleaved graphite surfaces bearing deposited gold (Au) nanostructures (～10 nm in diameter) by using sensitive pump-probe reflectivity spectroscopy with ultrashort (7.5 fs) laser pulses. We observed enhancement of phonon amplitudes (C=C stretching modes) in the femtosecond time domain, considered to be due to the enhanced electromagnetic (EM) field around the Au nanostructures. Finite-difference time-domain (FDTD) calculations confirmed the EM enhancement, The enhancement causes drastic increase of coherent D-mode (40 THz) phonon amplitude and nanostructure-dependent changes in the amplitude and dephasing time of coherent G-mode (47THz) phonons. This methodology should be suitable to study the basic mechanism of SERS and may also find application in nanofabrication