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Potassium tantalates, K2Ta2O6 and KTaO3, were synthesized by hydrothermal route. The crystal structural, optical, and adsorption properties of tantalates were investigated in the manuscript. The results indicate that the initial concentration of KOH is the determinate factor of crystal structure of tantalates. When the concentration of KOH is lower than 6M, the product is K2Ta2O6. While when the concentration is higher than 7M, the main product is KTaO3. Optical properties of tantalates analysis shows that the band gap of K2Ta2O6 is larger than that of KTaO3, which may be due to the different electronic band structure originating from the different overlapping way of the atomic orbital of tantalum and oxygen. The adsorption performance study shows that the adsorption property of K2Ta2O6 is higher than that of KTaO3, which would be assigned to its larger surface area. [ABSTRACT FROM AUTHOR]

The effect of nitrogen concentration on the interfacial and optical properties, as well as band offsets of HfTiO thin films by rf sputtering HfTi alloy target has been systematically investigated. The results indicate that an interfacial layer is unavoidably formed between HfTiON thin films and Si substrate, and the main content of the interfacial layer is silicate. No silicide is formed in the interfacial layer which is partly responsible for the poor electrical properties of high-k gate dielectrics. The optical properties of HfTiON films change, such as the refractive index decreases, while the extinction coefficient increases with the increase of N content, due to the defects increase in the films. The results also indicate that the bandgap and VB offset reduce with the introduction of N into HfTiO thin films. The CB offset of the HfTiON thin films is almost unchanged indicating that the N concentration has little effect on CB offset. However, the bandgap and band offsets are all higher than 1 eV, the sufficient band offsets still makes sputtering-derived HfTiON films by HfTi alloy target a promising high-k gate dielectric for future complementary metal oxide semiconductor technology. [ABSTRACT FROM AUTHOR]

Thickness-modulated optical dielectric constants and band alignments of HfOxNy films grown by sputtering have been investigated by spectroscopic ellipsometry (SE) and x-ray photoelectron spectroscopy. Based on SE measurements, it has been noted that an increase in optical dielectric constant and band gap has been observed as a function of the film thickness. Analyses of thickness-dependent band alignment of the HfOxNy/Si system indicate that the valence band offset increases, but only slight change in the conduction band offset, resulting from the thickness-induced change in the structure. The suitable optical dielectric constants and band offsets relative to Si make sputtering-derived HfOxNy film a promising candidate for high-k gate dielectrics. [ABSTRACT FROM AUTHOR]

Composition-dependent electronic structure and optical properties of Hf1-xSixOy (0.1≤x≤0.6) gate dielectrics on Si at 450 °C grown by UV-photo-induced chemical vapor deposition (UV-CVD) have been investigated via x-ray photoemission spectroscopy and spectroscopy ellipsometry (SE). By means of the chemical shifts in the Hf 4f, Si 2p, and O 1s spectra, the Hf–O–Si bondings in the as-deposited films have been confirmed. Analyses of composition-dependent band alignment of Hf1-xSixOy/Si gate stacks have shown that the valence band (VB) offset (ΔEv) demonstrates little change; however, the values of conduction band offset (ΔEc) increase with the increase in the silicon atomic composition, resulting from the increase in the separation between oxygen 2p orbital VB state and antibonding d states intermixed of Hf and Si. Analysis by SE, based on the Tauc–Lorentz model, has indicated that decreases in the optical dielectric constant and increase in band gap have been observed as a function of silicon contents. Changes in the complex dielectric functions and band gap Eg related to the silicon concentration in the films are discussed systematically. From the band offset and band gap viewpoint, these results suggest that Hf1-xSixOy films provide sufficient tunneling barriers for electrons and holes, making them promising candidates as alternative gate dielectrics. [ABSTRACT FROM AUTHOR]

High-k gate dielectric YOxNy films were prepared by reactive sputtering. The effects of postdeposition annealing on the structure and optical properties of YOxNy films have been investigated. The x-ray diffraction result shows that the crystallization starts at the annealing temperature of 500 °C. Spectroscopic ellipsometry was employed to determine the optical properties of a set of YOxNy films annealed at various temperatures. It was found that the refractive index (n) of YOxNy films decreased with the increase of annealing temperature below 600 °C, whereas it increased with increasing annealing temperature above 600 °C. The annealing-temperature dependence of the optical band gap of YOxNy films was also discussed in detail. It has indicated that the optical band gap of YOxNy films shifts to higher energy after higher temperature annealing, which is likely due to the reduction of N content and the change of crystalline structure in YOxNy films. [ABSTRACT FROM AUTHOR]

N-doped ZnO films were prepared by annealing zinc oxynitride films deposited by rf reactive sputtering. Two Raman peaks were observed at 274 and 580 cm-1. According to the variation of the integral intensity of these two peaks, the nitrogen activation at 500 °C [the activation temperature (AT)] has been obtained. Below the AT, the integral intensities of them show a different variation trend. X-ray photoelectron spectroscopy (XPS) indicates the N chemical state variation for them and finds the activated Zn-N bond. Further analyses by photoluminescence (PL) spectra and spectroscopic ellipsometry (SE) have been carried out. The activated sample exhibits a symmetric emission peak at 3.22 eV assigned to be the A0X emission at room temperature. SE investigation takes account of samples within the different temperature span divided by the AT. Different factors, such as nitrogen dopant (N)O and the nanocrystal growth, which affect the redshift of the absorption edges, have been discussed. [ABSTRACT FROM AUTHOR]

The structural stability and optical properties of ultrathin HfAlOx films grown by facing-target reactive sputtering, depending on the postannealing temperature, have been determined via x-ray photoelectron spectroscopy and spectroscopic ellipsometry (SE). By virtue of the chemical shifts of Hf4f, Al2p, and Si2p core-level spectra, it has been found that the structural stability of HfAlOx/Si system sustains up to 800 °C. However, the breaking of the Hf–Al–O bond and the phase separation take place drastically at the annealing temperature of 900 °C. In particular, the information of an interfacial Si–O–Si bond as the dominant reaction during the postannealing treatment has been observed, confirmed by Fourier transform infrared spectroscopy. Analysis by SE, based on the Tauc-Lorentz model, has indicated that increase in the refractive index and reduction in thickness has been observed as a function of annealing temperature, originating from the annealing-induced higher packing density. The change of the complex dielectric functions and bandgap Eg correlated with the annealing temperature are discussed in detail. [ABSTRACT FROM AUTHOR]

The microstructure and optical dielectric constants of HfOxNy thin films deposited by using radio frequency reactive magnetron sputtering have been investigated at various substrate temperatures. Fourier transform infrared spectroscopy spectra indicate that an interfacial layer has been formed between the Si substrate and the HfOxNy thin film during deposition. Spectroscopy ellipsometry (SE) results show that the substrate temperature has a strong effect on physical properties of HfOxNy thin films such as refractive index n and extinction coefficient k. Meanwhile, the optical dielectric functions of the films have determined using SE data and optical absorption properties of HfOxNy thin films deposited at different substrate temperatures have also been studied. [ABSTRACT FROM AUTHOR]

A high-k Hf-silicate interfacial layer grown by the solid phase reaction between sputtered metallic Hf films and an underlying SiO2/Si substrate through in situ vacuum annealing and subsequent thermal oxidation has been investigated. By means of the chemical shifts of Si 2p, Hf 4f, and O 1s core-level spectra determined by x-ray photoelectron spectroscopy (XPS), the formation of an interfacial Si-O-Si bond as the dominant reaction during in situ thermal oxidation of the Hf/SiO2/Si gate stack has been confirmed. In situ vacuum anneals without air exposure at 700 °C accelerates the interface reaction and results in the formation of Si-rich Hf-silicate interfacial layer. Analysis by Fourier transform infrared spectroscopy (FTIR) has indicated that vacuum annealed samples containing the silicate interface layer effectively suppresses the growth of the interfacial SiOx layer compared to unannealed samples during postdeposition annealing. [ABSTRACT FROM AUTHOR]

Rutile structured SnO[sub 2] nanobelts have been synthesized from the mixture of Sn powders and SiO[sub 2] nanoparticle powders. Each nanobelt has a uniform width of about several hundred nanometers and a thickness of about tens of nanometers along its entire length. Micro-Raman spectrum measurement on the SnO[sub 2] nanobelts shows that the first-order Raman A[sub 1g] mode (632.9 cm[sup -1]) is very strong, and two weak Raman bands 498 and 694 cm[sup -1] seem to correspond to infrared (IR)-active longitudinal optical (LO) and transverse optical (TO) of A[sub 2u] modes. In addition, the IR spectrum of the SnO[sub 2] nanobelts shows the A[sub 2u] (LO) (701.9 cm[sup -1]) and E[sub u (1)] (TO) (634.5 cm[sup -1]) modes and one surface mode (565.2 cm[sup -1]). The IR-active bands in the Raman spectrum and the surface mode in IR spectrum, which may be due to the nanoscale morphology of the nanobelts. [ABSTRACT FROM AUTHOR]

Studies ballistic electronic transport in a proposed mesoscopic structure, quantum cable. Uniqueness of the structure quantum cable for the study of mesoscopic transport; Correlation between Fermi energy of electrons and ballistic conductance of quantum cable; Impact of the accidental degeneracies of the transverse subbands of quantum cable on the quantum conductance units.

Presents information on a study that investigated direct current resistivity and its temperature dependence for macrostructured NiAl. Types of defects in n-material; Two aspects in which the interaction of interfaces with the conduction electrons is manifested.

The effect of nitrogen incorporation on the band alignment and electrical properties of HfTiO gate dielectric complementary metal-oxide-semiconductor (MOS) capacitors has been investigated by spectroscopy ellipsometry, x-ray photoelectron spectroscopy, and electrical measurements. Reduction in optical band gap and band offsets has been detected. However, improved electrical properties have been achieved from HfTiON gate dielectric MOS capacitors attributed to the nitrogen-induced reduction in oxygen-related traps and the improved interface quality. Although there is a nitrogen-induced reduction in band gap and band offset, the sufficient barrier heights still makes HfTiON a promising high-k gate dielectric candidate for proposed near-future complementary metal-oxide-semiconductor applications. [ABSTRACT FROM AUTHOR]

In this letter, treatment of GaAs surface by using dimethylaluminumhydride-derived AlON passivation layer prior to HfO2 deposition is proposed to solve the issue of Fermi level pinning. It has been found that AlON passivation layer effectively suppresses the oxides formation and leads to the Fermi level unpinning at the interface between GaAs and HfO2. Based on analysis from metal-oxide-semiconductor capacitors of Au/HfO2/AlON/GaAs stack, excellent capacitance-voltage characteristics with saturated accumulation capacitance and reduced leakage current have been achieved, which may originate from the decrease in the interface state density and the increase in the conduction band offset. [ABSTRACT FROM AUTHOR]

Wide-bandwidth random lasing action is observed from the randomly assembled ZnS/ZnO biaxial nanobelt heterostructures under optical excitation. This is because optical gain at ultraviolet regime can be obtained from the near-band-edge radiative recombination of ZnS and ZnO. Surface defects related radiative recombination centers of ZnS and ZnO nanostructures also contribute to the visible optical gain. Hence, a broadband optical gain is obtained from the ZnS/ZnO biaxial nanobelt heterostructures. Moreover, a wide bandwidth coherent optical feedback can be achieved from the randomly assembled biaxial nanobelts due to high refractive index contrast between the nanobelts and air. [ABSTRACT FROM AUTHOR]

Fermi level pinning attributed to oxides at the GaAs/high-k interface is a major obstacle to develop GaAs-based metal-oxide-semiconductor devices with high performance. In this letter, thermal nitridation treatment of GaAs surface prior to the high-k deposition is proposed to solve the issue of interface pinning. Results have confirmed that nitridation passivation effectively suppresses the oxides formation and leads to a shift in the Fermi level toward the conduction band minimum on the GaAs surface, which increases the conduction band offset at the GaAs/AlOxNy interface, followed by a saturated accumulation capacitance with reduced gate leakage current. [ABSTRACT FROM AUTHOR]

The effect of nitrogen atom doping on the optical properties and dielectric constant of HfO2 films has been systematically investigated. Spectroscopic ellipsometry was employed to investigate the optical properties of nitrogen incorporated HfO2 films. The values of average oscillator strength and average oscillator position extracted from spectroscopic ellipsometry demonstrated that nitrogen incorporation could influence the dipole oscillator strength and oscillator position of HfO2. A physical model of dipole structures was proposed to verify the enhancement of dielectric constant of HfO2 films by nitrogen incorporation. [ABSTRACT FROM AUTHOR]

The effect of N concentration on the band gap and band offsets of HfOxNy films has been systematically investigated. It was found that the band gap as well as the band offsets of HfOxNy films decreased with the increase of N concentration. When the N concentration reached 16.3%, the conduction band offset (ΔEc) reduced to be 0.88 eV, which is smaller than the minimal requirement of ΔEc values for high-k dielectrics and, thus, leads to unacceptably high leakage currents. Therefore, nitrogen concentration should be carefully controlled to guarantee excellent properties of nitrogen incorporated high-k dielectrics. [ABSTRACT FROM AUTHOR]

Effects of nitrogen incorporation on interfacial property, band gap, and band alignments of high-k Y2O3 gate dielectrics have been investigated. It was found that the incorporation of nitrogen into Y2O3 films can effectively suppress the growth of the interfacial layer between Y2O3 and Si substrate. The incorporation of nitrogen into Y2O3 films leads to the reduction of band gap and valence band offset, but not the conduction offset of Y2O3 films. High temperature annealing will help to increase the band gap and valence band offset of YOxNy film due to the release of the interstitial N atoms. [ABSTRACT FROM AUTHOR]

Temperature-dependent interfacial chemical bonding states and band alignment of HfOxNy/SiO2/Si gate stacks have been investigated by X-ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry (SE). By means of the chemical shifts of Hf 4f, Si 2p, O 1s, and N 1s core-level spectra, it has been found that the chemical stability of the HfOxNy/SiO2/Si stacks strongly depends on the annealing temperature. Analysis of temperature-dependent band alignment of HfOxNy/SiO2/Si stacks suggests that the valence band offset ΔEv increases slowly from 1.82 eV for as-grown film to 2.55 eV for annealed film at 700 °C; however, the values of conduction band offset ΔEc only demonstrates a slight change in the vicinity of 1.50 eV. From the band offset viewpoint, HfOxNy/SiO2/Si gate stack could be a promising candidate for high-k gate dielectrics. [ABSTRACT FROM AUTHOR]

A ZrO2/TiO2/Si gate stack has been prepared by using solid phase reaction between sputtered ZrO2/Ti stack and underlying SiO2/Si substrate through in situ vacuum annealing. X-ray photoelectron spectroscopy was used to analyze interfacial properties of the ZrO2/TiO2/Si stack after annealing at high temperatures. The interfacial silicate is composed of Ti silicate and ZrO2 layer does not take part in the interfacial reaction to form Zr silicate. Such a stack has the advantage of combining high dielectric constant of ZrO2 and excellent interfacial property of Ti silicate/Si interface, and will have potential applications in the advanced metal-oxide-semiconductor devices. [ABSTRACT FROM AUTHOR]

The colloidal, highly crystalline, and size-controlled ZnS nanorods have been prepared through a thermal decomposition of single-source-precursor approach in oleylamine solution. The length and width of nanorods can be controlled simply by varying the molar ratio of zinc 2-mercaptobenzothiazole complex and oleylamine or prolonging the anneal duration. Optical and electrochemical properties of different sizes of ZnS nanorods are discussed and size-dependent optical and electrochemical band gaps are evidently observed, which show a direct correlation between the electronic spectra and electrochemical band gap. [ABSTRACT FROM AUTHOR]

One-dimensional chains consisting of crystalline Fe3O4 nanoparticles have been synthesized by using a polyacrylic acid template method. The characterizations of composition, structure, and magnetic property of the chains are performed. The formation mechanism of Fe3O4 nanocrystal chains is proposed to be a polymer template and magnetostatic interaction. In a weak magnetic field, the synthesized nanochains can be reorganized. The as-synthesized nanochains are ferromagnetic at room temperature with lower saturation magnetization and higher coercivity value than those of bulk Fe3O4, which could have potential applications in nanosensors for rapid and sensitive detection of biologic or chemical molecules. [ABSTRACT FROM AUTHOR]

Carbon-encapsulated ZnSe nanoparticles with diameters about 50 nm were synthesized by noncatalytic one-step thermal evaporation method. The ZnSe cores have a wurtzite crystal structure. The as-synthesized products are uniform and composed of single-crystalline ZnSe nanoparticles enwrapped with polycrystalline graphite layers. The photoluminescence measurement of the carbon-encapsulated nanoparticles shows that the blue emission enhances dramatically compared with the naked ZnSe nanoparticles. This synthetic strategy might exploit a favorable route to synthesize carbon-encapsulated semiconductor nanostructures, which are potentially important for optoelectronic nanodevices. [ABSTRACT FROM AUTHOR]

Thermal stability and energy-band alignment of ZrOxNy films on Si are investigated using x-ray photoelectron spectroscopy and spectroscopy elliposometry (SE). The results show that the Zr–N bonds in as-oxidized ZrOxNy films are thermally unstable, while the N–O bonds in ZrOxNy matrix are stable even at high annealing temperature of 900 °C. Optical properties are also analyzed based on the SE fitting results. The slight blueshift in the absorption edge indicates the increased band gap from 3.9 to 5.1 eV after the additional annealing. Based on the valence-band spectrum results, zero-field energy-band alignments for ZrOxNy/Si and ZrOxNy/SiO2/Si stacks are extracted. [ABSTRACT FROM AUTHOR]

We report in this letter that Hafnium oxynitride (HfOxNy) gate dielectrics were prepared by radio frequency (RF) reactive magnetron sputtering and optical properties of the HfOxNy thin films were investigated by spectroscopic ellipsometry with photon energy of 0.75–6.5 eV at room temperature. The investigations showed that the annealing temperatures have a strong effect on the optical properties of HfOxNy thin films. With increased annealing temperature, the refractive index n is observed to increase, while the extinction coefficient k decreases, respectively. The changes of the complex dielectric functions and the optical band gap Eg with the annealing temperature are also discussed. [ABSTRACT FROM AUTHOR]

ZnS nanowires with periodically alternating twins along the growth direction of wires have been synthesized via a thermal evaporation method. Structural characterizations reveal that both sphalerite (cubic) and wurtzite (hexagonal) phases coexist in the synthesized nanowires. The periodically twinned ZnS nanowires are formed through the vapor-solid mechanism. High quality of the nanowires is confirmed by the optical absorption and the photoluminescence observations combined with large ratio surface and interfaces induced by the twin modulations. The perfect crystal structure indicates their potential applications in nanoscience and nanotechnology. [ABSTRACT FROM AUTHOR]

Bi nanotubes embedded in anodic alumina membranes were fabricated by pulsed electrodeposition. Scanning electron microscope, x-ray diffraction, and high-resolution transmission electron microscope analyses revealed that the Bi nanotubes are highly oriented and single crystalline. Electronic transport measurements proved that there is a metal–semiconductor transition of Bi nanotube arrays with the decrease of the wall thickness of the nanotubes, and this transition depends only on the wall thickness and is independent of the diameter of the nanotubes. The quantum confinement effect is believed to play an important role in determining transport properties. The Bi nanotubes may find applications in thermoelectric nanodevices. [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]

Monoclinic structured β-Ga2O3 nanobelts have been synthesized through a simple thermochemical route at low temperature in range of 400–500 °C. Each nanobelt has a uniform width of about several hundred nanometers and a thickness of about 10 nm along its entire length. Micro-Raman spectrum of the β-Ga2O3 nanobelts shows that the four weak Raman bands at 112, 146, 170, and 266 cm-1 which seem to correspond to infrared (IR)-active transverse optical (TO) Au mode and/or longitudinal optical (LO) Bu mode, respectively. The IR-active bands in the Raman spectrum and the surface mode in the IR spectrum may relate to the nanoscale morphology of the nanobelts. [ABSTRACT FROM AUTHOR]

The lattice parameter of bismuth nanowires has been measured using the in situ high-temperature x-ray diffraction method. Single-crystalline Bi nanowire arrays with the diameters from 10 nm to 250 nm have been fabricated within the porous anodic alumina membranes by a pulsed electrodeposition technique. Different temperature dependencies of lattice parameter and thermal expansion coefficient were found for Bi nanowires with different diameters, and there is a transition from positive thermal expansion coefficient at low temperature to negative one at high temperature, and the transition temperature shifts to high temperature with the increase in the diameter of Bi nanowires. [ABSTRACT FROM AUTHOR]

Spectroscopic ellipsometry with photon energy 0.75–6.5 eV at room temperature has been used to derive the optical properties of nitrogen-incorporated HfO2 films on Si(100) substrates grown by radio-frequency reactive sputtering using different N2/(N2+O2+Ar) gas ratios from 20% to 50%. Excellent agreement has been found between the experimental and the simulated spectra, in which an empirical dielectric dispersion relation based on Tauc-Lorentz model has been successfully adopted. Increases in the refractive index n and the extinction coefficient. k, with increases in nitrogen-incorporation content are observed due to the nitrogen-incorporation-induced higher packing density. The change of the complex dielectric functions and reduction in the optical band gap with an increase in nitrogen concentration resulting from the effect of the nitrogen-incorporation on the structure are discussed in detail. [ABSTRACT FROM AUTHOR]

Mn-doped ZnS nanobelts have been prepared through a thermal evaporation method starting with a mixture of acetylacetonates and H[sub 2]S at 900 °C. The nanobelts had a uniform single-crystal hexagonal wurtzite structure and grew along [001] direction. Undoped ZnS nanobelts and ZnMnS nanobelts with 1%, 3%, and 5% Mn so obtained have been characterized by x-ray diffraction, energy dispersive x-ray analysis, and photoluminescence (PL) spectra. PL measurements showed that the fluorescence efficiencies increased and the glow peaks shifted to longer wavelengths as the Mn-doped ratios increased, and the doping was found responsible for the changes in the defect-related emission of the ZnS nanobelts. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

S-doped ZnO nanowires with an average diameter of 80 nm and length up to several tens of micrometers were produced through a simple physical evaporation approach. The nanowires had a single-crystal hexagonal structure and grew along the [102] direction. Photoluminescence (PL) measurements showed that the doping of sulfur shifted the PL spectrum peak towards short wavelengths, and the doping quantity was found responsible for the different characteristics. [ABSTRACT FROM AUTHOR]

Monoclinic gallium oxide (β-Ga[sub 2]O[sub 3]) nanowires were synthesized by heat treating a composite material of GaAs and pre-evaporated Au at 1240 °C in dry oxygen atmosphere. The catalytic Au metal generated liquid nanoclusters that serve as reactive sites confining and directing the growth of β-Ga[sub 2]O[sub 3] nanowires during the vapor-liquid-solid growth process. The β-Ga[sub 2]O[sub 3] nanowires have diameters ranging from 20 to 50 nm and lengths of several micrometers. Photoluminescence measurement under excitation at 250 nm shows that the bulk β-Ga[sub 2]O[sub 3] nanowires have a stable blue emission at 475 nm and an ultraviolet emission at 330 nm, which may be related to the defects such as the oxygen vacancy and the gallium-oxygen vacancy pair. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Highly ordered TiO[sub 2] nanowire (TN) arrays were prepared in anodic alumina membranes (AAMs) by a sol-gel method. The TNs are single crystalline anatase phase with uniform diameters around 60 nm. At room temperature, photoluminescence (PL) measurements of the TN arrays show a visible broadband with three peaks, which are located at about 425, 465, and 525 nm that are attributed to self-trapped excitons, F, and F[sup +] centers, respectively. A model is also presented to explain the PL intensity drop-down of the TN arrays embedded in AAMs: the blue PL band of AAMs arises from the F[sup +] centers on the pore walls, and the TNs first form in the center area of the pores and then extend to the pore walls. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Ag/Si nanocomposite films were prepared by the radio-frequency magnetron cosputtering method. The fine structure of the plasmon resonance absorption peak was found in film samples. X-ray photoelectron spectroscopy analysis indicated that the samples were composed of a two-layer structure, which accounted for the structure of the optical absorption spectra. The peak located near 445 nm is the plasmon resonance absorption peak of Ag nanoparticles embedded in a partially oxidized Si matrix. Its intensity decreases with decreasing film thickness and disappears in a very thin sample. The peak located near 380 nm originates from the plasmon resonance absorption of the thoroughly oxidized surface layer of the sample. Its intensity does not change with increasing thickness, but it cannot be observed in the very thick sample. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Nanocomposite films consisting of nanosized Ag particles embedded in partially oxidized amorphous Si matrices were prepared by radio frequency cosputtering deposition. Subsequent heat treatment at different temperatures ranging from 200 to 500 °C and its effects on the optical absorption of the films were investigated by spectrometry in the wavelength ranging from 200 to 1200 nm. "Surface resonance state" is introduced to discuss the broadening, blue-shift, and intensity decrease of the plasmon resonance absorption peak with decreasing Ag particle size. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Large-scale of crystalline GaN nanowires (diameter∼50 nm) have been fabricated through chemical-vapor deposition in the nanochannels of the anodic alumina template. X-ray diffraction and selected area electron diffraction pattern investigations indicate that the nanowires are single crystal with hexagonal wurtzite structure. A typical scanning electron microscopy image and the energy dispersive x-ray spectroscopy results indicate that indium nanoparticles only act as catalyst in GaN nanowires growth. At room temperature, photoluminescence spectrum of the GaN nanowire arrays shows a visible broadband with three peaks, which are located at about 363, 442, and 544 nm. The light emission may be attributed to GaN band-edge emission, the existence of defects or surface states, and the interaction between the ordered GaN nanowires and anodic alumina membrane. The growth mechanism of crystalline GaN nanowires is discussed. The method makes it possible to synthesize other nitride nanowire arrays. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Single-crystalline Bi nanowires with diameters ranging from 20 to 70 nm were prepared by electrodeposition using nanoporous aluminum oxide membranes rather than the more usual track-etched polycarbonate membranes. X-ray diffraction and selected area electron diffraction investigations revealed that the nanowires are essentially single crystalline and highly oriented. The temperature dependence of zero-field resistance of different diameter nanowires indicated that these Bi nanowires undergo a semimetal-semiconductor transition due to two-dimensional quantum confinement effects. The resistance maximum was observed at 50 K in zero magnetic field for 20 nm Bi nanowires, while the resistance minimum at 258 K for 50 nm Bi nanowires, due to the quantum size effect. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Ordered semiconductor In[sub 2]O[sub 3] nanowire arrays are uniformly assembled into hexagonally ordered nanochannels of anodic alumina membranes (AAMs) by electrodeposition and oxidizing methods. Their microstructures were characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. A blue-green photoluminescence (PL) band in the wavelength range of 300–650 nm was observed in the In[sub 2]O[sub 3]/AAM assembly system. The PL intensity and peak position depend on the annealing temperature, which is mainly attributed to the singly ionized oxygen vacancy in the In[sub 2]O[sub 3] nanowire array system. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We propose that quantum cables can be used as a kind of transport spectroscope to obtain directly the quasi-one-dimensional (Q1D) density of states (DOS) of cylindrical quantum wires. By simultaneously measuring the direct current through the cylindrical quantum wire and the leaky tunneling current into its neighboring wire at desirable temperatures, one can obtain detailed information about the Q1D DOS and subband structure of the cylindrical quantum wire. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Ordered semiconductor ZnO nanowire arrays embedded in anodic alumina membranes (AAM) were fabricated by generating alumina templates with nanochannels, electrodepositing Zn in them, and then oxidizing the Zn nanowire arrays. The polycrystalline ZnO nanowires with the diameters ranging from 15 to 90 nm were uniformly assembled into the hexagonally ordered nanochannels of the AAM. Photoluminescence (PL) measurements show a blue PL band in the wavelength range of 450-650 nm caused by the singly ionized oxygen vacancy in ZnO nanowires. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]