Search

Studies the optical properties of epitaxially grown zinc oxide (ZnO) thin films on sapphire using pulsed laser deposition. Application of zinc oxide in semiconductors; Details on the experiment; Crystal qualities of ZnO.

The pressure-induced B3–B1 phase transition and some interesting thermodynamic properties for B3 structure of ideal stoichiometric technetium mononitride (TcN) have been studied systematically by first-principles calculations. It is found that TcN has a B3 ground-state phase at zero pressure and the transition pressure from B3 to B1 structure determined by the energy vs volume curves is about 35 GPa. Through the quasi-harmonic Debye model, the dependences of thermal expansion coefficient, constant-volume heat capacity, and constant-pressure heat capacity of TcN with B3 phase on temperature up to 1600 K are successfully predicted at 0, 10, 20 and 35 GPa pressures, respectively. [ABSTRACT FROM AUTHOR]

Highlights: [•] The thermal expansion of MgF2 with a fluorite-type structure has been investigated. [•] The quasi-harmonic Debye model is applied to take into account the thermal effect. [•] Particular attention is paid to the prediction of thermal expansion for the first time. [ABSTRACT FROM AUTHOR]

Abstract: The pressure–volume–temperature relationship and bulk modulus of ZnO with zinc-blende phase are investigated by means of first-principles density functional theory calculations combined with the quasi-harmonic Debye model in which the phononic effects are considered. Particular attention is paid to the predictions of the first and second pressure derivatives of isothermal bulk modulus which play central role in the formulation of approximate equations of state for the first time. The properties of ZnO with zinc-blende phase are summarized in the pressure range of 0–7.45GPa and the temperature up to 2000K. [Copyright &y& Elsevier]

Abstract: Because of the significance of the first and second pressure derivatives of the isothermal bulk modulus, a detailed theoretical study of the high-pressure rocksalt phase of ZnO under high pressure and temperature has been carried out by means of first-principles density functional theory calculations combined with the quasi-harmonic Debye model in which the phononic effects are considered. Particular attention is paid to the predictions of the isothermal bulk modulus and its pressure derivatives which play central role in the formulation of approximate equations of state for the first time. [Copyright &y& Elsevier]

Abstract: The growth of hydrogenated carbon film from CH radicals is studied by classical molecular dynamics simulation for various incident energies (3.25–130eV). The impingement of CH radical and its effect on the microstructure of formed film are carefully analyzed. It is found that the sp3-C fraction is almost identical to the H concentration for all films; both of them decrease with increasing incident energy. To deposit hydrogenated carbon film with fine smoothness, the energy of incident CH should be 10–70eV. At other energies (either lower or higher), deposited films are of roughness and with some chain-like structures at surface. Different growth mechanisms behind these observations are discussed. [Copyright &y& Elsevier]

Abstract: We have performed one-phase molecular dynamics (MD) simulations to investigate the melting curve of NaCl over a wide range of pressures. To ensure faithful MD simulations, two types of potentials, the shell-model (SM) and the two-body rigid-ion Born–Mayer–Huggins–Fumi–Tosi (BMHFT) potentials, are fully tested. Compared with SM potential, the MD simulation with BMHFT potential is very successful in reproducing accurately the measured volumes of NaCl. The BMHFT potential can also produce a satisfactory melting curve, consistent with both experiments and two-phase simulations. Hence we recommend that the BMHFT should be the reliable potential for simulating high-pressure properties of NaCl. [Copyright &y& Elsevier]

Abstract: A detailed theoretical study of the isothermal and adiabatic bulk moduli of MgF2 with a fluorite structure under high pressure and temperature has been carried out by means of first-principles density functional theory calculations combined with the quasi-harmonic Debye model in which the phononic effects are considered. Particular attention is paid to the prediction of the isothermal bulk modulus and its first and second pressure derivatives for the first time. The calculated ground state properties agree well with other theoretical values. At extended pressure and temperature ranges, the variation of the bulk modulus which plays a central role in the formulation of approximate equations of state has also been predicted. The properties of MgF2 with a fluorite structure are summarized in the pressure range of 0–135 GPa and the temperature up to melting temperature 1500 K. [Copyright &y& Elsevier]

Abstract: Highly transparent conductive Ga-doped ZnO (GZO) thin films have been prepared on glass substrates by metal organic chemical vapor deposition. The effect of Ga doping on the structural, electrical and optical properties of GZO films has been systematically investigated. Under the optimum Ga doping concentration (∼4.9at.%), c-axis textured GZO film with the lowest resistivity of 3.6×10−4 Ωcm and high visible transmittance of 90% has been achieved. The film also exhibits low transmittance (<1% at 2500nm) and high reflectance (>70% at 2500nm) to the infrared radiation. Furthermore, our developed GZO thin film can well retain the highly transparent conductive performance in oxidation ambient at elevated temperature (up to 500°C). [Copyright &y& Elsevier]

Abstract: Molecular dynamics (MD) simulations have been performed to investigate the effects of pressure and temperature on the isothermal bulk modulus of CaO using pair-wise interactions that include polarization effects through the shell model (SM). The dependence of isothermal bulk modulus B T of CaO on the compression ratio V/V 0 and pressure P have been obtained from MD runs at T=300K, and compared with the available experimental data and other theoretical results. A good agreement between theory and experiment is obtained. Meanwhile, B T dependence on temperature T at zero pressure is investigated. At extended pressure and temperature ranges, SM–MD method has also been carried out for predicting the P–V–T equation of state and isothermal bulk modulus at different temperatures along the isotherms 0, 1000, 2000, 3000, and 4000K, and at different pressures along the isobars 5, 15, 30, 40, and 50GPa for CaO, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Shell-model molecular dynamics simulation has been performed to investigate the melting of the major Earth-forming mineral CaO at elevated temperatures and high pressures, based on thermal instability analysis. The interatomic potential is taken to be the sum of effective pair-wise additive Coulomb, van der Waals attraction, and repulsive interactions. It is shown that the simulated molar volume of CaO is successful in reproducing recent experimental data and our DFT-GGA calculations up to the core–mantle boundary pressure of 135 GPa. The pressure dependence of the simulated high pressure melting temperature of CaO is in good agreement with the results obtained from the Lindemann melting equation at a pressure of below 7 GPa. The extrapolated melting temperatures are in good agreement with the results obtained from Wang’s empirical model up to 60 GPa. The predicted high pressure melting curve, being very steep at lower pressures, rapidly flattens on increasing pressure. The thermodynamic properties of the rocksalt phase of CaO are summarized in the 0–135 GPa pressure range and for temperatures up to 9300 K. [ABSTRACT FROM AUTHOR]

Abstract: First-principles plane-wave pseudopotential density functional theory method with the ultrasoft pseudopotential scheme in the frame of the GGA correction is performed to calculate the phase transition and the bulk modulus of the PtC. The phase transition from zinc-blende structure to rock-salt structure occurs at the pressure of 475kbar. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the dependences of cell volume and lattice constant on temperature at 0 pressure, the isothermal bulk modulus and its pressure derivative on pressure along the isotherms 0, 500, 1000, 1500, 2000, and 2500K, are also successfully obtained. [ABSTRACT FROM AUTHOR]

Abstract: A study of one-dimensional exciton diffusion in tris(2-phenylpyridine) iridium(III) molecules as a function of intermolecular spacing is reported. We show for the first time the existence of an optimum intermolecular spacing that gives the longest diffusion length in [Ir(ppy)3] molecules. When the intermolecular spacing is too short, the long-range excitonic quenching becomes dominant; on the other hand, when it is too long, the exciton energy transfer is miniscule. A specially-designed organic light-emitting diode with separate exciton formation and emission was constructed to measure the one-dimensional exciton diffusion length. The maximum one-dimensional exciton diffusion length for this material is around 8.5nm for an inter-molecular separation of around 4.5nm. [Copyright &y& Elsevier]

Abstract: Molecular dynamics simulations have been performed to investigate the thermal expansivity of MgO at high temperature using the very similar Lewis–Catlow and Stoneham–Sangster shell model potentials. In order to take account of non-central forces in crystals, the breathing shell model is also introduced in simulation. The volume thermal-expansion coefficient α P of MgO dependence of the temperature T at 0 and 135GPa have been obtained and compared with the available experimental and theoretical results. Compared with shell model potentials, the molecular dynamics results obtained using breathing shell model potentials are more compressible. At an extended pressure and temperature ranges, α P has also been predicted. [Copyright &y& Elsevier]

Abstract: The constant temperature and pressure molecular dynamics (MD) have been performed to investigate the isothermal bulk modulus of MgO under high pressures and temperatures, using the shell model (SM) potential functions consisted of the Coulomb, dispersion, and repulsion interactions. In order to take account of non-central forces in crystals, the breathing shell model (BSM) is also introduced in MD simulation, in which the repulsive radii of oxygen ions are allowed to deform isotropically under the effects of other ions in the crystal, with each core and breathing shell being linked by a harmonic spring with force constant k. The isothermal bulk modulus K T of MgO dependence of the compression ratio V/V 0 and the pressure P have been obtained from MD runs at T =300 and 2000K, and compared with the available theoretical results. Compared with SM potential of Stoneham and Sangster [Phil. Mag. B 52 (1985) 717], the MD results with potential of Lewis and Catlow (LC) [J. Phys. C 18 (1985) 1149] are found to be in good agreement with the studies based on ab initio calculations, and the results obtained using BSM potential are more compressible. Meanwhile, K T dependence of temperature T at zero pressure is investigated. At an extended pressure and temperature ranges, K T has also been predicted. The properties of MgO are summarized in the pressure 0–200GPa ranges and the temperature up to 3500K. [Copyright &y& Elsevier]

Abstract: We report a highly efficient electrophosphorescent bis(2-phenylquinoline) (acetylacetonate) iridium(III) [Ir(2-phq)2(acac)]-based red organic light-emitting diode. The emission layer consists of a periodic thin layer of guest material of Ir(2-phq)2(acac) separated by host material of 4,4′-Bis(carbazol-9-yl)biphenyl. The guest and host thicknesses were optimized independently to obtain the best performance. The current efficiency reaches to a maximum of 16.2cd/A then drops to 15 and 11cd/A at brightness of 10 and 100cd/m2, respectively. By reducing the thickness of the host layer, the power efficiency was further improved. Device with a maximum power efficiency of 8.3lm/W was obtained. We also found that the concentration quenching in Ir(2-phq)2(acac) is dominated by molecular aggregation. Excitonic quenching by radiationless Förster process is miniscule. [Copyright &y& Elsevier]

Abstract: n-ZnO nanorod/p-CuAlO2 heterojunction light-emitting diodes have been fabricated on p+-Si substrates. The CuAlO2 thin film was deposited by dc-magnetron sputtering while the ZnO nanorods (NRs) were fabricated using the vapor-phase transport method. The current–voltage characteristics of the devices showed good rectifying behavior with a high forward-to-reverse current ratio of around 120 at ±7V. Strong ultraviolet electro-luminescence centered at ∼390nm and a broad green-band emission were observed from the diode at room-temperature. The p-CuAlO2 layer was found to facilitate hole injection from p+-Si into n-ZnO while confining the electrons at ZnO/CuAlO2 interface, thus effectively enhancing the recombination emission efficiency in ZnO NRs. [Copyright &y& Elsevier]

Abstract: The pressure–volume–temperature (P–V–T) equation of state (EOS), isothermal bulk modulus, and thermal expansivity of CaF2 with cubic fluorite-type structure are investigated using the constant temperature and pressure shell model molecular dynamics (MD) method with effective pair potentials which consist of the Coulomb, dispersion, and repulsion interaction. It was shown that MD simulation is very successful in accurately reproducing the measured volumes of the CaF2 over a wide range of pressures. The simulated P–V data matched X-ray diffraction experimental results up to 9.5GPa at 300K. In addition, volume thermal-expansion coefficient and isothermal bulk modulus were also calculated and compared with available experimental data and the latest theoretical results at ambient condition. At extended temperature and pressure ranges, The P–V EOS under different isotherms at selected temperatures, T–V EOS under different isobars at selected pressures, thermal expansivity, and isothermal bulk modulus were predicted up to 1500K and 10GPa. The detailed knowledge of thermodynamic behavior and EOS at extreme conditions are of fundamental importance to the understanding of the physical properties of CaF2. [Copyright &y& Elsevier]

Abstract: Two different potential models of molecular dynamics (MD) simulations have been applied to investigate the pressure–volume–temperature (P–V–T) relationship and lattice parameter of NaCl under high pressure and temperature. The first one is the shell model (SM) potentials in which due to the short-range interaction pairs of ions are moved together as is the case in polarization of a crystal due to the motion of the positive and negative ions, and the second one is the two-body rigid-ion Born–Mayer–Huggins–Fumi–Tosi (BMHFT) potentials with full treatment of long-range Coulomb forces. The P–V relationship at 300K, T–V relationship at zero pressure, and lattice parameter a, have been obtained and compared with the available experimental data and other theoretical results. Compared with SM potentials, the MD simulation with BMHFT potentials is very successful in reproducing accurately the measured volumes of NaCl. At an extended pressure and temperature ranges, P–V relationship under different isotherms at selected temperatures, T–V relationship under different pressures, and lattice parameter a have also been predicted. The properties of NaCl are summarized in the pressure range 0–30GPa and the temperature up to 2000K. [Copyright &y& Elsevier]

Abstract: Shell model molecular dynamics (MD) method is used to predict the structure and thermodynamic properties of MgO at high temperatures and high pressures using the Stoneham–Sangster and Lewis–Catlow potentials, respectively. In order to account for the observed large departures from the Cauchy relation of the elastic constants of the MgO, the breathing shell model (BSM) is also introduced in MD simulation, in which the repulsive radii of oxygen ions are allowed to deform isotropically under the effects of other ions in the crystal. The properties including the expansivity, constant-pressure heat capacity, isothermal bulk modulus are calculated in a wide range of temperatures (300–3000K) and pressures (0–150GPa). The obtained structural and thermodynamic parameters are compared with the available experimental data and other theoretical results. Compared with Stoneham–Sangster and Lewis–Catlow potentials, the MD simulation with BSM is very successful in reproducing accurately the measured volumes of MgO and the results are more compressible. Meanwhile, some thermodynamic parameters have been predicted at elevated temperatures and high pressures. The detailed knowledge of thermodynamic behavior of the major Earth-forming mineral—periclase (MgO) at extreme P–T conditions are of fundamental importance to our understanding of the Earth''s lower mantle and the history of the Earth''s formation. [Copyright &y& Elsevier]

Abstract: We report on a blue fluorescent [4,4′-bis(9-ethyl-3-carbazovinylene)-1-1′-bisphenyl] organic light-emitting diode with a sequentially doped device architecture introduced recently. The emission layer consists of a few repeating cells, similar to a multiple quantum well structure, which are made of sequentially evaporated host and guest layers. An external quantum efficiency as high as 2.8% photons/electron was obtained, comparable with that fabricated using the conventional doping method. Without degrading the efficiency, devices with varied emission spectra (peak wavelength shifted from 472 to 488nm) were produced by simply varying the guest layer thickness. The spectrum shift is due to changes in local order or aggregate state, or both. [Copyright &y& Elsevier]

Abstract: A novel morphology of zinc oxide (ZnO) consisting of resistor-shaped nanowires connected “in-series” has been synthesized by a vapor phase transport method in the presence of water and copper. Scanning electron microscopy showed that the diameter of nanowires changes abruptly from ∼200 to ∼20nm and forms a resistor-shaped nanostructure. Transmission electron microscopy and selected-area electron diffraction revealed a grain boundary at the thicker center (200nm) and the nanowires were composed of a pair of crystallites of wurtzite ZnO growing along ±[0001] directions. A growth mechanism is proposed which takes into account the crystal growth conditions, the catalytic effect of water and copper, as well as the inherent polarization of the wurtzite structure along its c-axis. [Copyright &y& Elsevier]

Abstract: Bandgap engineering by insertion of a hole-blocking layer (HBL) between the hole-injection layer (HIL) and hole-transporting layer (HTL) for green and blue-emitting organic light-emitting device is shown to improve the current efficiency by 30% and 70%, respectively. The improvement was attributed to a better electron–hole balance in the device. Two different organic materials, 2,9-dimethyl-4,7-diphenylphenanthroline and tris-(8-hydroxyqunoline) aluminum were used as HBL. Variation of HBL and HTL thickness was shown to adjust the current efficiency and operating voltage, respectively. Insertion of a thin HBL between HIL and HTL for blue-emitting devices also resulted in appearance of multicolor emission which was used to produce a pure white light. [Copyright &y& Elsevier]

Abstract: Molecular dynamics (MD) simulations have been performed to investigate the pressure–volume–temperature (P–V–T) relationship of MgO under high pressures and temperatures using the very similar shell model (SM) potentials with those of Stoneham and Sangster (SS) [Philos. Mag. B 52 (1985) 717] and Lewis and Catlow (LC) [J. Phys. C 18 (1985) 1149]. In order to take account of non-central forces in crystals, the breathing shell model (BSM) is also introduced in MD simulation, in which the repulsive radii of oxygen ions are allowed to deform isotropically under the effects of other ions in the crystal, with each core and breathing shell being linked by a harmonic spring with force constant k. The lattice parameter a, thermoelastic parameter αK T, and P–V relationship under different isotherms at selected temperatures and T–V relationship at zero pressure, have been obtained and compared with the available experimental data and other theoretical results. Compared with SM-SS and SM-LC potentials, the MD simulation with BSM is very successful in reproducing accurately the measured volumes of MgO. At an extended pressure and temperature ranges, P–V–T relationship has also been predicted. The properties of MgO are summarized in the pressure range of 0–2000kbar and the temperature up to 5000K. [Copyright &y& Elsevier]

Tubular ZnO microstructure arrays were fabricated on a large scale by a two-step hydrothermal method. The porous ZnO tubular structures were then used to construct a gas sensor for CO detection. The microtube array gas sensor showed sensitive response to different concentration of CO with an optimum temperature of 250 °C. Because of the large surface to volume ratio, the sensitivity of the microtube arrays was about twice of that of the ZnO rods. Our results indicate that this simple two-step method for fabrication of large-scale tubular microstructure arrays can be potentially used in gas sensor applications with improved performance. [ABSTRACT FROM AUTHOR]

Abstract: A comparative study of in situ post-growth annealing of organic layers before hole-blocking layer (HBL) or metal cathode deposition was conducted on tris-(phenyl-pyridyl)-iridium complex, Ir(ppy)3-based phosphorescent organic light-emitting devices (PHOLED). The devices were fabricated in the same run with a standard device without annealing for comparison, with an identical structure of indium tin oxide (ITO)/copper phthalocyanine (CuPc) (10nm)/N,N′-di(naphthalene-l-yl)-N,N′-diphenyl-benzidine (NPB) (90nm)/4,4′-bis(carbazol-9-yl)-biphenyl (CBP):Ir(ppy) (40nm)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) (15nm)/tris(8-hydroxy-chinolinato) aluminum (Alq3) (40nm)/Mg:Ag (200nm)/Ag (20nm). The annealing temperature used was 60, 80 and 100°C, before deposition of BCP HBL or before Mg:Ag cathode, respectively. It was found that, before BCP deposition, 60°C in situ post-growth annealing improves performance of the device, and the devices decay significantly with 80 and 100°C annealing. The in situ post-growth annealed organic layers were characterized by photoluminescence and Raman spectroscopy. [Copyright &y& Elsevier]

Abstract: The pressure–volume–temperature () relationship, lattice constant and isothermal bulk modulus of ZnO with zinc-blende cubic structure are studied using the constant temperature and pressure shell model molecular dynamics method with effective pair potentials which consist of the Coulomb, dispersion, and repulsion interaction. It is shown that the calculated structural and thermodynamic parameters including equilibrium volume, lattice constant, isothermal bulk modulus and its pressure derivative at standard condition are in good agreement with the available experimental data and the latest theoretical results. In addition, the isothermal and isobaric properties are discussed on the basis of the corresponding relationship, and the volume compression data and isothermal bulk modulus data are predicted up to 300 kbar at 300 K, 1000 K, and 1500 K. The thermodynamic properties of the zinc-blende phase of ZnO are summarized in the 0–300 kbar pressure range and for temperature up to 2000 K. [Copyright &y& Elsevier]

Abstract: The heat capacities at constant pressure and constant volume, and thermal expansivity are calculated for ZnO with rocksalt-type and zinc-blende-type cubic structures over a wide range of temperatures using molecular dynamics simulations with interactions due to effective pair-wise potentials which consist of the Coulomb, dispersion, and repulsion interaction. It is shown that the calculated structural and thermodynamic parameters including lattice constant, thermal-expansion coefficient, isothermal bulk modulus and its pressure derivative at ambient condition are in good agreement with the available experimental data and the latest theoretical results. At extended pressure and temperature ranges, lattice constant and heat capacity have also been predicted. The structural and thermodynamic properties of ZnO with cubic structure are summarized in the 300–1500 K temperature ranges and up to 100 kbar pressure. [Copyright &y& Elsevier]

Abstract: The refractive indices of textured indium tin oxide (ITO) and zinc oxide (ZnO) thin films were measured and compared. The ITO thin film grown on glass and ZnO buffered glass substrates by sputtering showed distinct differences; the refractive index of ITO on glass was about 0.05 higher than that of ITO on ZnO buffered glass in the whole visible spectrum. The ZnO thin film grown on glass and ITO buffered glass substrates by filtered vacuum arc also showed distinct differences; the refractive index of ZnO on glass was higher than that of ZnO on ITO buffered glass in the red and green region, but lower in the blue region. The largest refractive index difference of ZnO on glass and ITO buffered glass was about 0.1 in the visible spectrum. The refractive index variation was correlated with the crystal quality, surface morphology and conductivity of the thin films. [Copyright &y& Elsevier]

Abstract: Zinc oxide (ZnO) quantum dots (QDs) were fabricated on silicon substrates by metal organic chemical vapor deposition. Formation of QDs is due to the vigorous reaction of the precursors when a large amount of precursors was introduced during the growth. The size of the QDs ranged from 3 to 12nm, which was estimated by high-resolution transmission electron microscopy. The photoluminescence measured at 80K showed that the emission of QDs embedded film ranged from 3.0 to 3.6eV. The broad near-band-edge emission was due to the quantum confinement effect of the QDs. [Copyright &y& Elsevier]

Abstract: The high pressure melting curve of MgO is simulated by using the constant temperature and pressure molecular dynamics method combined with effective pair potentials which consist of the Coulomb, dispersion, and repulsion interaction at high pressure and high temperature. It is shown that the simulated molar volume of MgO is very successful in reproducing accurately the recent experimental data over wide pressure ranges. The pressure dependence of the simulated high pressure melting temperature of MgO is in good agreement with the latest theoretical data. The simulated high pressure melting curve of MgO up to lower mantle pressure, being rather steep at lower pressures, rapidly flattens on increasing pressure. At the core–mantle boundary pressure of 135 GPa MgO melts at 7500 K, which is significantly higher than the extrapolations of the currently available experimental data derived by Zerr and Boehler. [Copyright &y& Elsevier]

Abstract: The effect of surfactants on the electro-optical properties of holographic polymer dispersed liquid crystal (HPDLC) Bragg gratings was studied in detail. The experimental results showed that surfactants could effectively reduce the driving voltage. The morphologies of HPDLC Bragg grating surface were also investigated by scanning electron microscope (SEM). The threshold electric field was reduced from 13V/μm to about 2.3V/μm and the switching electric field was 27.3V/μm. The rising time and the falling time were 60μs and 80μs, respectively. [Copyright &y& Elsevier]

Abstract: Zinc oxide nanowhiskers with multipod structures have been fabricated on copper-coated Si wafer by sintering the mixture of ZnO and graphite powders in air. The multipod nanowhisker shows tetrapod, tripod and hexapod morphologies with legs of 100–500nm in diameter and several microns in length. The legs of the multipod nanowhisker intercross at a central knot of the whisker. The octahedron twin nucleus is responsible for the tetrapod structure and possibly responsible for the tripod structure as well. The hexapod structure is due to a stacked nucleus of two octahedron nuclei. [Copyright &y& Elsevier]

Abstract: A magnetic field-induced current-modulating opamp (MCMOP) based on the CMOS differential Tesla–Volt multiplier (TVM) cell for magnetic field-effect transistor (MAGFET) 1/f noise reduction is reported. It consists of a CMOS differential TVM cell made of a pair of identical MAGFETs, a fully differential opamp, and a set of chopper-stabilization switches. Due to the modulation effect of the input voltage on the magnetic field-induced current imbalance, the MCMOP is utilized as a linear magnetic sensor not only to amplify the magnetic signal, but also to chop and stabilize the signal, so as to suppress the low frequency noise in the MAGFETs themselves. By introducing the MCMOP, the magnetic noise level of the magneto-opamp (MOP) consisting of the same differential opamp and the same single MAGFET is reduced from 160 to 25μT/Hz1/2 at 1Hz. This is a 16dB improvement of the magnetic resolution. [Copyright &y& Elsevier]

Abstract: Nickel induced lateral crystallization of amorphous silicon with and without electric field has been studied. Dendritic silicon growth behavior is observed, with crystallites of a few hundred nanometers in width and up to a few microns in length. The behavior can be understood from the preferential epitaxial growth of silicon from the (111) facets of the NiSi2 precipitate, which forms during the early stage of the annealing process. The dendritic growth fronts are different with and without electric field in the nickel induced lateral crystallization process. Electric field is found to be beneficial in increasing the lateral crystallization rate and improving the film crystallinity. Joule heating plays an important role as well to enhance the lateral crystallization. [Copyright &y& Elsevier]

Abstract: Based on a vapor-phase transport process, self-organized nanocomb structures of ZnO were fabricated on Au-coated Si substrate by employing a mixture of ZnO and graphite powders as source materials. The morphology of the product showed a ribbon-like stem and nanorod array aligned evenly along one side of the nanoribbon. It was found that the nanoribbon grew mainly along direction and the self-assembled branching nanorods grew epitaxially along [0001] orientation from the (0002) plane of the stem. The growth process was analyzed in detail. [Copyright &y& Elsevier]

Zinc oxide nanostructures (nanowires, nanobelts, and nanofibers) were fabricated on gold-coated silicon (1 0 0) substrate via a simple thermal chemical reactions vapor transport deposition (TCRVTD) method in air with a mixture of ZnO and carbon powders as reactants. The growth process was carried out at 1100 °C in a quartz tube with one side open to the air. The gold film acted as a metal catalyst. There is no carrier gas in the process. The ZnO nanostructures were characterized by the scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy, and room temperature photoluminescence (PL) spectroscopy. The growth mechanism is explained by thermal chemical reactions and vapor–liquid–solid growth mechanism. [Copyright &y& Elsevier]

The polycrystalline silicon thin film and gate oxide of poly-Si TFTs were treated by NH3/N2O plasma or their combination to improve the reliability of TFTs. The poly-Si TFTs with and without NH3/N2O plasma treatment were characterized by measuring the transfer curves of poly-Si TFTs. The results showed that the characteristics of poly-Si TFTs treated with NH3/N2O plasma were greatly improved at hot-carrier stress and thermal accelerated tests. The reason is that nitrogen atoms terminate the dangling bonds and improve the characteristics of poly-Si TFTs. [Copyright &y& Elsevier]

Polycrystalline indium–tin-doped oxide (ITO) thin films have been fabricated on Si(1 1 1) and quartz substrates by filtered cathodic vacuum arc (FCVA) technique for the first time. The ITO thin films were deposited at different substrate temperature and oxygen gas flow rates into the reactor chamber. The films deposited at low temperature below 100 °C are amorphous. The films grown between 200 and 350 °C mainly oriented in the (2 2 2), (4 0 0), (4 4 0), and (6 2 2) directions both on silicon substrate and quartz substrate. The optimized ITO film has a high transmittance of about 95% in the wavelength range of 400–800 nm, the volume resistivity is 6.57×10−4 Ω cm and the electron carrier concentration is as high as 1.62×1021 cm−3. Atomic force microscopy (AFM) images show that the surface of ITO film is very smooth both on silicon and quartz substrates, the RMS average roughness is 2.24 nm for silicon substrate and 2.43 nm for quartz substrate respectively. [Copyright &y& Elsevier]

Zinc oxide (ZnO) crystal fibers were prepared on silicon (1 0 0) substrate via a simple thermal chemical reactions vapor transport deposition method in air with a mixture of ZnO and carbon powders as reactants. The growth process was carried out at 1100°C in a quartz tube with one side opened to the air. There is no other metal catalyst and carrier gas in the process. The scanning electron microscope measurements showed that the ZnO fibers obtained had diameters ranging from 300 nm to 1.5 μm and the maximal lengths up to 1 mm, resulting in an aspect ratio estimated as high as about 600. The ZnO fibers were also characterized by X-ray diffraction, Raman spectroscopy, and room temperature photoluminescence spectroscopy. The growth mechanism is explained by chemical reactions and vapor–liquid–solid mechanism. [Copyright &y& Elsevier]

Nanostructural zinc oxide has been successfully fabricated by heating the mixture of ZnO and graphite powders in air. The growth of these zinc oxide nanostructures with respect to the growing time and temperature has been studied. The morphologies and the crystal structures have been characterized by scanning electronic microscopy and the X-ray diffraction. The results indicated that ZnO nanostructure formed mainly along the crystal orientation [002] on silicon substrate at moderate temperatures. The crystallization was improved by prolonging growth time and the morphologies mainly depended on the distribution of the growth temperature. The growth process was attributed to vapor-liquid-solid mechanism. [ABSTRACT FROM AUTHOR]

β-Sialon powder was fabricated by carbothermal reduction–nitridation of natural Chinese Yixing kaolin at 1300–1550 °C in nitrogen atmosphere, using carbon black as a reducing agent. The effect of reaction temperature, holding time, nitrogen flow rate and the amount of carbon black on the synthesis of β-sialon powder and its solid solution degree (z value) have been investigated systematically. The phases of the reaction products are identified by XRD. The results indicate that the products of reaction are more sensitive to the reaction temperature than holding time. Nearly all β-sialon is produced at a temperature of 1450 °C for 6 h. Higher temperatures lead to the presence of SiC phase. A slight amount of carbon favors the carbothermal reduction of kaolin and excess carbon results in the conversion of β-sialon to SiC. The z value of β-sialon (Si6−zAlzOzN8−z) rises with the duration of holding time and varies from 2 to 2.8 as the holding time varies from 2 to 6 h at 1450 °C. [Copyright &y& Elsevier]

In this paper, a new hydrogenation process of poly-Si thin film for the fabrication of poly-Si thin film transistors (TFTs) is proposed. In the new approach, the hydrogenation of TFTs is performed before deposition of contact metal. N-channel and p-channel poly-Si TFTs with various channel lengths and widths were fabricated with the new and conventional processes for comparison. The results verified that the efficiency of hydrogenation has been improved remarkably by the new process. The field-effect mobility of carriers, the on state current, threshold voltage and the on/off states current ratio have been greatly improved, and the trap state density has been reduced significantly. [Copyright &y& Elsevier]

By introducing two methyl groups into 6 and 7 positions of the chromene group of a red fluorescent dye, 4-dicyanomethylene-2 (p-diphenylaminostyryl)-chromene (DCCPA), we have successfully synthesized a red organic materials, 4-dicyanomethylene-6,7-dimethyl-2 (p-diphenylaminostyryl)-chromene (DCCMPA) of considerably better florescence properties than DCCPA. Both photoluminescent (PL) and electroluminescent (EL) properties of DCCPA and DCCMPA have been examined and compared. The PL quantum yield of DCCMPA is 21% higher than that of DCCPA. The devices with DCCMPA doped into tris (8-quinolinolato) aluminum (Alq3) also show higher efficiencies than the DCCPA doped devices. Based on these experimental results, some useful guidelines for molecular design of red organic materials for EL applications are discussed. [Copyright &y& Elsevier]

Examines the relationship of human papillomavirus (HPV) type to grade of cervical intraepithelial neoplasia (CIN) in a large series of cases. Study design, patients and results; Evidence implicating human papillomavirus in the pathogenesis of cervical cancer; Suggestion that the identification of HPV type may be used as a significant determinant of how patients with low-grade CIN are managed; More.

Abstract: A focus-switchable liquid crystal (LC) lens made of polymer–LC composite was fabricated by a molding technique. The focus-switchable LC lens fabricated had a diameter of 6.0mm and center thickness of 67μm. The focal length obtained was about 48cm. The lens showed good optical properties and strong polarization dependence. Its focus can be switched either by applying a low driving voltage (about 3V) or by changing the polarization of the incident light. Such focus-switchable polymer–LC lens fabricated by this kind of technique is potentially useful in many optical systems, such as optical tweezers, machine vision, eye glasses. [Copyright &y& Elsevier]

Gallium-doped nanostructural zinc oxide fibers have been fabricated by vapor-phase transport method of heating the mixture of zinc oxide, gallium oxide, and graphite powders in air. The zinc oxide fibers grew along [002] direction, forming a vertically aligned array that is predominantly perpendicular to the substrate surface. With a gallium doping concentration of 0.73 at. %, the corresponding carrier concentration and resistivity were 3.77×10[sup 20] cm[sup -3] and 8.9×10[sup -4] Ω cm, respectively. The field emission of these vertically aligned ZnO fiber arrays showed a low field emission threshold (2.4 V/μm at a current density of 0.1 μA/cm[sup 2]), high current density, and high field enhancement factor (2317). The dependence of emission current density on the electric field followed Fowler–Nordheim relationship. The enhanced field emission is attributed to the aligned structure, good crystal quality, and especially, the improved electrical properties (increased conductivity and reduced work function) of the nanofibers due to gallium doping. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A four-electrode liquid crystal cell, featuring a double-side fringe-field switching, has been designed with two-layer electrodes on both glass substrates. The two-layer electrode is the same as that used in fringe-field switching liquid crystal displays. Using a negative dielectric liquid crystal, a homogeneous cell has been fabricated with top and bottom stripe electrodes perpendicular to each other. The fringe fields near top and bottom surfaces drive the homogeneous liquid crystal layer to a twisted structure. The distributions of electric field and molecular director are obtained by theoretical analysis. The double-side fringe-field switching cell shows a much faster response and wider viewing cone compared to traditional fringe-field switching one. The improved electro-optical properties are due to the wider and more symmetric director distribution with respect to the midplane of the liquid crystal cell. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In the current work, the aim is to report systematic results from first-principles calculations with density functional theory (DFT) on three cubic structures, rock salt (NaCl-type), zinc blende (ZnS-type), and cesium chloride (CsCl-type), of ZnN under high pressure. From the enthalpy versus pressure relations, we find that the NaCl-type phase of ZnN is more stable than the ZnS-type phase when the pressure higher than 2.55 GPa and high-pressure NaCl-type phase will stabilize up to 150 GPa. Through the careful evaluation with the quasi-harmonic Debye model, a complete set of thermodynamic data up to 2000 K, including PVT equation of state, isothermal bulk modulus, Debye temperature, Grüneisen parameter, thermal expansivity, heat capacity, and entropy for the ZnN with high-pressure NaCl-type structure is achieved. This set of data is considered as the useful information to understand the high-temperature and high-pressure properties of ZnN. [ABSTRACT FROM AUTHOR]

Thermal expansion coefficient, heat capacity, and Grüneisen parameter of iridium phosphide Ir 2 P are reported by means of quasi-harmonic Debye model for the first time in the current study. This model combines with first-principles calculations within generalized gradient approximation using pseudopotentials and a plane-wave basis in the framework of density functional theory, and it takes into account the phononic effects within the quasi-harmonic approximation. The Debye temperature as a function of volume, the Grüneisen parameter, thermal expansion coefficient, constant-volume and constant-pressure heat capacities, and entropy on the temperature T are also successfully obtained. All the thermodynamic properties of Ir 2 P in the whole pressure range from 0 to 100 GPa and temperature range from 0 to 3000 K are summarized and discussed in detail. [ABSTRACT FROM AUTHOR]