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The valence band offset (VBO) of a n-ZnO/p-MgxNi1-xO heterojunction grown by pulsed laser deposition was investigated by x-ray photoelectron spectroscopy. From the directly measured VBO of 1.64 ± 0.05 eV, a -2.26 ± 0.05 eV conduction band offset was derived. This indicates that the ZnO/MgxNi1-xO heterojunction has a type-II (staggered) band alignment. The conduction band minimum (CBM) of the n-ZnO/p-MgxNi1-xO heterojunction shifts to higher energy with Mg doping relative to the n-ZnO/p-NiO heterojunction. Thus, the position of the CBM can be controlled by the Mg concentration. [ABSTRACT FROM AUTHOR]

The N2 atmosphere postannealing is introduced to improve the interfacial quality and the dielectric properties of HfO2 films prepared by pulsed laser deposition. The disappearance of interface layer between HfO2 film and Si substrate and the decrease of leakage current densities after annealing are further confirmed by high-resolution cross-sectional transmission electron microscopy investigation and electrical measurement. Electric conduction analysis results show that the dominant leakage current conduction mechanisms of the annealed HfO2 film are the Schottky emission at low electric field, the trap-assisted tunneling, and space-charge-limited current at high electric field for the gate and substrate injections, respectively. [ABSTRACT FROM AUTHOR]

The discharge chemistry of CHF3 in 27/2, 60/2, and 60/13.56 MHz dual-frequency capacitively coupled plasmas (DF-CCPs) is studied with actinometric optical emission spectroscopy and mass spectrometry. The frequency effect on the generation of reactive species was investigated. The reactive radicals and the density ratio of F/CF2 could be controlled by the 2 MHz rf power in 27/2 and 60/2 MHz DF-CCPs. The density ratios of F/CF2 in 27/2 and 60/2 MHz DF-CCPs are observed to increase with an increase in low-frequency power. However, this control could not be obtained in 60/13.56 MHz DF-CCP. [ABSTRACT FROM AUTHOR]

The photoluminescence properties of nitrogen-incorporated SnO2 thin films on Si (100) substrates deposited by reactive magnetron sputtering have been studied. A strong photoluminescence band centered at 3.696 eV with full width at half maximum of 0.2 eV has been observed at room temperature. The peak position of the emission shifts to higher energy with increasing excitation intensity or decreasing temperature. The emission is considered due to the localized exciton recombination, and the observed exciton localization and band-tail states are believed to originate from the potential fluctuation induced by spatial distribution fluctuations of nitrogen concentration and/or grain boundary defects in the nanocrystalline film. [ABSTRACT FROM AUTHOR]

Hollow cadmium selenide (CdSe) tetrapods were synthesized on a large scale. The directional growth of twins led the tetrapod nanostructure to be formed. The silicon powder was responsible for the growth of the hollow tetrapods. The UV-visible absorption spectra of the hollow CdSe tetrapods display an absorption edge at about 765 nm. There is a redshift of 53 nm of the absorption edge, in comparison with that of bulk CdSe at 712 nm. In the Raman spectra, two new anomalous modes at 250.91 and 493.42 cm-1 are observed. This might originate from the enhanced internal stress of hollow structures. [ABSTRACT FROM AUTHOR]

The optical properties of δ-Bi2O3 thin films were investigated using spectroscopic ellipsometry and optical absorption spectrum. δ-Bi2O3 thin films were grown on Si and quartz substrates under different oxygen flow ratios (OFR) by radio frequency reactive magnetron sputtering. The Tauc-Lorentz dispersion method was adopted to model the optical dispersion functions of the thin films. The optical bandgap was obtained by three different methods. It was found that refractive index and extinction coefficient decrease, and the optical bandgap has a slight blue shift with increasing the OFR. Factors influencing the optical constants and optical bandgap are discussed. [ABSTRACT FROM AUTHOR]

A series of Al-doped amorphous silicon oxide films have been grown on p-type silicon (100) substrates by a dual ion beam cosputtering method. Visible electroluminescence (EL) from the devices, made by films with different contents of Al, can be seen with the naked eye under forward bias and reverse bias for films containing sufficient amounts of Al. The EL spectra are found to have a luminescence band peaked at 510 nm (2.4 eV), which is the same result as that obtained from silicon oxide films. With the increase in the amounts of Al, the peak position does not shift, the onset of the bias decreases, and the intensity of EL peak increases. Experiment results show that the doping of Al is beneficial to improving the conduction condition of films while the structure of the films associated with luminescence centers is affected hardly at all. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Investigates trap levels in sol-gel derived polycrystalline Pb(Zr,Ti)O[sub 3] thin films using deep level transient spectroscopy (DLTS). Fabrication of metal-ferroelectric-metal capacitor structures using a constant voltage DLTS system; Observation of prominent peaks associated with a single trap level; Measurement of the activation energy.

Thin films of the high Tc superconducting Y-Ba-Cu metal oxide have been prepared for the first time by plasma-assisted organometallic chemical vapor deposition using β-diketonate chelates of Y, Ba, and Cu, Y(C11H19O2)3, Ba(C11H19O2)2, and Cu(C11H19O2)2 as starting materials, followed by post-annealing under a reduced pressure of oxygen stream. X-ray diffraction spectra indicate that the films deposited on the yttria-stabilized zirconia (YSZ) substrate have a significant preferential orientation of the crystallite c axis being perpendicular to the substrate surface. Four-probe resistivity measurements reveal the temperature of the onset of superconductivity at 91.6 K and zero resistance by 78.5 K. [ABSTRACT FROM AUTHOR]