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Electron and hole spin lifetimes and spin relaxation processes in diluted magnetic semiconductor spin superlattices were investigated using dc photoluminescence analysis. The results showed that the long hole spin lifetime was due to the strain-induced splitting of the bulk-degenerate light- and heavy-hole bands at the zone center which inhibited fast spin relaxation.

The temperature-dependent reflectance (R) and photoluminescence (PL) measurements on ZnMnO films grown by plasma-assisted molecular beam epitaxy is studied. The spectral data of ZnMnO films have not only shown the deterioration of crystalline quality with increasing Mn composition fraction but has also indicated the Mn clustering caused by Mn atom segregation.

The dependence of the hot-electron energy relaxation in InN epilayers on electron density and the electron temperature of the hot electrons are determined. The density-dependent electron energy loss rate in InN is explained by a combination of longitudinal optical and acoustic phonon emissions and a slowing of the energy loss rate at high electron densities is attributed to piezoelectric coupling to acoustic phonons.

Pressure-induced resonant Raman scattering is adopted to analyze the zone-center optical phonon modes and crystal characteristics of [Zn.sub.1-x][Mn.sub.x]Te thin films. The results have shown that the manganese ions have increased the iconicity of ZnTe under ambient conditions, whereas an external hydrostatic pressure has reduced the iconicity and the bond length of [Zn.sub.1-x][Mn.sub.x]Te.

Capacitance and dissipation factor measurements at a temperature of 200K

Abstract: In this study, measurements of titration alkalinity (TA), total dissolved carbon dioxide (TCO2), and δ 13C of TCO2 () throughout the water column at the SouthEast Asian time-series study (SEATS) site were investigated in order to understand better the fundamental processes controlling their vertical distributions in the South China Sea (SCS). The linear correlations between TA and salinity in the shallow waters, as identified by the mixing line between the surface water and salinity maximum water suggested the predominant control of physical mixing on the variability of TA. In contrast, TCO2 and showed the non-conservative behavior in the respective TCO2 and vs. salinity plot due to the effect of biological production. A stoichiometric model further showed that the depth profile of NTA (=TA×salinity/35) largely reflects the increase of preformed NTA in the shallow waters, whereas carbonate dissolution was responsible for the continuous increase of NTA in the deep waters. A one-dimensional diffusion–advection model further revealed that the carbonate dissolution could account for 28% of NTCO2 (=TCO2×salinity/35) increase in deep waters, and the remaining 72% of NTCO2 was from organic decomposition. Calculation of excess TA further showed that it emerged well above the aragonite and calcite saturation depths at 600 and 2500m, respectively, indicating that some biologically, chemically, and physically-mediated processes must be involved to provide excess TA into the shallow waters. The decrease in with depth primarily resulted from organic decomposition. The influence of anthropogenic CO2 throughout the water column was assessed with the carbon chemistry and the isotope-based approach in this study. Both methods obtained nearly the same results in which the signal of anthropogenic CO2 decreased exponentially with depth, and its penetration depth were found to be at ∼1000m. The inventory of anthropogenic CO2 in the water column was estimated to be ∼16.6molCm−2, which was less than that reported in the northwest Pacific at the same latitude, presumably due to the enhanced upwelling in the SCS. Such an anthropogenic CO2 penetration had led to decreases of the saturation levels of aragonite and calcite by 17% and 14%, respectively, in the surface water, and an upward migration of aragonite saturation depth by ∼100m since industrial revolution. [Copyright &y& Elsevier]

Abstract: The structural properties of TiO2 nanotubes with rapid thermal annealing (RTA) and traditional thermal annealing in O2 were studied by X-ray diffraction (XRD) and Raman scattering measurements. From analyzing the line width of XRD and the correlation length of the Raman peak, we demonstrate that RTA can be an effective tool for amorphous–anatase transformation in TiO2 nanotubes. The Raman peak redshifts and reduces its line width after thermal annealing and RTA, which may involves the reduction of oxygen-related defects. [Copyright &y& Elsevier]

Abstract: We have studied the temperature dependence of the band gap and the decay dynamics of isoelectronic ZnSe1−x O x (x=0−0.053) semiconductors, using photoluminescence (PL) and time-resolved PL spectroscopy. The temperature dependence of the band gap of ZnSe1−x O x decreases with the increase in O concentration. The Kohlrausch law is in good agreement with the O-induced complex decay profiles. As temperature increases, the mechanism of carrier decay undergoes a complicated change from trapped to free excitons. These findings are consistent with the temperature dependence of the stretching exponent β. [Copyright &y& Elsevier]

Zn1−xMnxSe/ZnSe1−yTey (x=0.03, y=0.08) multiple-quantum-well structures were grown on GaAs substrates by molecular-beam epitaxy. Strong photoluminescence associated with iso-electronic Te traps was observed. A type-II band alignment was proposed for this class of quantum-well structures. Electrons were confined in the Zn1−xMnxSe layers. Holes were localized in the ZnSe1−yTey layers. The respective valence and conduction band offset were determined as 350±50 and 205±50 meV. [Copyright &y& Elsevier]

Compressive strain induced heavy hole and light hole splitting of the Zn1−xCdxSe epilayers grown by molecular beam epitaxy was studied by the reflectivity spectra. Heavy hole exciton (HHX) and light hole exciton (LHX) splittings for the ZnSe, Zn0.999Cd0.001Se, Zn0.987Cd0.013Se, and Zn0.974Cd0.026Se epilayers are 12.6, 14.0, 17.2 and 20.4 meV, respectively. HHX and LHX energy splitting depends linearly on the Cd composition. No strain relaxation was observed in these thin (about 50 nm) Zn1−xCdxSe epilayers. A simplified dielectric model was used to fit the reflectivity spectra. At 10 K, the obtained oscillator strength and broadening parameter are about 2.7×10−2 eV2 and 2.6 meV for HHX and 1.2×10−2 eV2 and 2.6 meV for LHX. Temperature dependence of HHX and LHX transition energy was fitted by Varshni’s and O’Donnell’s model. No clear temperature dependence was found for the HHX and LHX splitting. [Copyright &y& Elsevier]

Cd1−xZnxTe crystals were grown by the temperature gradient solution growth (TGSG). Optical properties of the Cd1−xZnxTe crystals were investigated by the photoluminescence (PL) spectroscopy. The full width at half maximum (FWHM) of 11 meV for the near band edge PL was obtained. The temperature dependent broadening of the PL line-width was fitted by the acoustic phonon, longitudinal optical phonon, and impurity interaction parameters. Defect radiative density is as low as 0.002. [Copyright &y& Elsevier]