Low-resistivity indium tantalum oxide films by magnetron sputtering

Low-resistivity Ta-doped In₂O₃ (InTaO) films from ceramic targets of In₂O₃ doped with 2, 5, and 10 wt% Ta₂O₅ were deposited on Corning glass # 1737 substrates by magnetron sputtering. The electrical and optical properties of these films were studied. The carrier type of InTaO films was found to be n-type. The resistivity, carrier density, and Hall mobility of InTaO films were in the range of 0.28–200.2×10^-4 cm, 0.2–7.4×10²⁰ cm^-3, and 3–31 cm²V^-1s^-1, respectively. A minimum resistivity of 2.8×10^-4 cm with a mobility of 31 cm²V^-1s^-1 and a high transparency of 85% in the visible were achieved for the InTaO thin films doped with 5 wt% Ta₂O₅. PACS 81.15.Cd; 81.40.Rs; 73.90.+f     

Cluster formation and laser-induced effects in the ablation of 2Cu(CO3)·Cu(OH)2. Time-of-flight mass spectrometric study

The mechanism of laser ablation of 2Cu(CO₃)·Cu(OH)₂ at 308 nm is investigated by time-of-flight mass spectroscopy at laser fluences in the range of 0.07 to 0.6 Jcm^-2. The neutral and ion composition of the plume reveals the presence of Cu, Cu₂O, CuO, H₂O and CO₂, which appear as free species or forming clusters. Plume composition is compatible with a thermal ablation mechanism which involves chemical processes similar to those reported for the purely thermal decomposition of the target. Velocity distributions of neutral species in the plume are measured and fitted to shifted Maxwell–Boltzmann time distributions; the best fitting yields flow velocities of 0.07 cms^-1 for CO₂ and Cu and 0.04 cms^-1 for Cu₂, which is compatible with an expansion regime characterized by weak interaction of the ejected particles. PACS 82.30.Nr; 78.70.-g     

Excitation of Intra-4f Shell Luminescence of Rare Earth Ions (Er3+ and Yb3+) by the Energy Transfer from Si Nanocrystals

Photoluminescence (PL) properties of SiO₂ films containing Si nanocrystals (nc-Si) and Er³⁺ (Yb³⁺) were studied. PL peaks attributable to the recombination of electron–hole pairs in nc-Si (1.5eV) and the intra-4f shell transition of Er³⁺ (0.81eV) (Yb³⁺ (1.26eV)) were observed simultaneously at room temperature. Correlation of the two peaks was studied as a function of nanocrystalline size. It was found that the intensity of the Er³⁺-related (Yb³⁺-related) peak increases drastically as the size of nc-Si decreases. Temperature dependence of PL spectra was studied. In the case of Yb-doped samples, temperature quenching of the PL became small as the size decreased, while in the case of Er-doped samples, no remarkable temperature dependence was observed. Two major features of the quantum size effects of nc-Si, i.e., the band-gap widening and the increase in the PL efficiency with decreasing the size, are thought to contribute to the improvement of room temperature PL efficiency of Er³⁺ (Yb³⁺).     

Rapid prototyping of micropower sources by laser direct-write

A laser forward-transfer and micromachining process has been developed to fabricate and optimize mesoscale electrochemical power sources, such as primary Zn–Ag₂O and secondary Li-ion microbatteries. The laser direct-write technique allows for adding, removing and processing the various material systems required for the fabrication of micropower sources on many types of substrates under ambient conditions. In this work, we demonstrate planar zinc–silver oxide alkaline cell configurations with 1.5–1.55 V open-circuit potentials. The 10 mm² samples show a flat discharge behavior under constant-current loads and capacities of 100 Ahcm^-2. Stacked Li-ion cells with 3.80-V open-circuit potentials have also been fabricated and continue to operate after 50 charge/discharge cycles. The 9 mm² samples exhibit capacities of 110 Ahcm^-2. PACS 81.16.Mk; 82.47.Aa; 82.47.Cb     

Generalized Transvectants-Rankin–Cohen Brackets

We introduce o(p+1q+1)-invariant bilinear differential operators on the space of tensor densities on Rⁿ generalizing the well-known bilinear sl₂-invariant differential operators in the one-dimensional case, called Transvectants or Rankin–Cohen brackets. We also consider already known linear o(p+1q+1)-invariant differential operators given by powers of the Laplacian.     

Influence of Hydrothermal Temperature on Structures and Photovoltaic Properties of SnO2 Nanoparticles

Two SnO₂ nanoparticles were synthesized by hydrothermal method at 170°C and 180°C, respectively. Transmission electron microscope observations reveal that the diameters of both the nanoparticles are around 6nm. At the same time, surface photovoltage spectroscopy measurements show that the nanoparticle synthesized at 180°C has more surface electronic states at 0.3eV below the conduction band than the one synthesized at 170°C. This means that the temperatures chosen in hydrothermal synthesis have significant influence on the surface electronic characteristics of resultant SnO² nanoparticles but the effect on their sizes is not obvious. However, after being calcined at 500°C for 2h, the diameter of the nanoparticle synthesized at 180°C increased to 23nm and that of the nanoparticle synthesized at 170°C increased to 32nm as calculated from X-ray diffraction pattern.     

Structural and thermoelectric properties in (Sb<Subscript>1-x</Subscript>Bi<Subscript>x</Subscript>)<Subscript>2</Subscript>Te<Subscript>3</Subscript> thin films

We have investigated the structural and thermoelectric properties of (Sb_1-xBi_x)₂Te₃ thin films on CdTe(111)B. Analysis of X-ray diffraction patterns (–2 scans and rocking curves) of the films shows that they are of high quality and that they are well aligned with their (00.1) axis normal to the substrates. Measurements of the temperature-dependent thermoelectric power, resistivity, and Hall coefficient of the films were performed with respect to the binary composition, x. For the samples in the range 0.2<x<0.3, the room-temperature thermopower values were in the range 159–184 V/K, the room-temperature carrier concentrations were 3.93–5.13×10¹⁹ cm^-3, and the room-temperature mobilities were 24.6–64.0 cm²V^-1s^-1. PACS 72.20.Pa; 72.80.Jc; 73.6l.Le     

Tailoring of the functional properties of sol–gel films on Pt/TiO2/SiO2/(100)Si substrates: (Pb,La)TiO3/(Pb,Ca)TiO3 multilayer heterostructures

Preferentially oriented sol–gel (Pb,Ca)TiO₃/(Pb,La)TiO₃/(Pb,Ca)TiO₃ and (Pb,La)TiO₃/(Pb,Ca)TiO₃/(Pb,La)TiO₃ multilayer heterostructure thin films deposited on silicon-based substrates have been studied and compared with identically prepared (Pb,La)TiO₃ (PTL) and (Pb,Ca)TiO₃ (PTC) films. The existence in their texture of two components that contribute to the net polarization in the direction normal to the plane of the film, 001 and 111, results in significant ferroelectric and pyroelectric properties. P_r=26 Ccm^-2 and =28.5×10^-9 Ccm^-2K^-1, and P_r=17 Ccm^-2 and =22.8×10^-9 Ccm^-2K^-1, have been achieved, respectively, in the PTL/PTC/PTL and PTC/PTL/PTC heterostructures. The surface roughness of these films provides a high specific surface that can be interesting for infrared detectivity. An increase of the dielectric permittivity in the whole temperature interval up to the transition temperature has been observed for both heterostructures with respect to the PTL and PTC films. This effect is due to a release of stress in the heterostructures that is revealed by the increase of the tetragonal distortion, c/a, of these films. PACS 68.55.Jk; 77.80.-e; 77.84.Dy     

Determination of thermal diffusivity of suspended porous silicon films by thermal lens technique

An alumina suspension containing 21 vol.% solids was made to flow through a needle at rates between 10^-12–10^-11 m³s^-1 and was subjected to electrostatic atomization at different applied voltages in the range 5–13 kV. The resulting modes of atomization were studied. The stable cone-jet mode was first obtained at 7 kV and 2.2×10^-12 m³s^-1 and the effect of increasing flow rate and applied voltage on the jet diameter was investigated. Using a pointed ground electrode the alumina droplets produced by the jet in the stable cone-jet mode were printed according to a pre-determined architecture. Alumina relic diameters in the print were <35 m. PACS 81.05.Je; 81.20.Ev; 81.20.Rg; 81.15.Pq; 47.27.Wg     

Ferroelectric and dielectric properties of Li-doped ZnO thin films prepared by pulsed laser deposition

Zinc oxide is a very important piezoelectric material with lower preparation temperature, simpler structure and composition. By doping with some elements having smaller ionic radii, such as lithium, to substitute the zinc ions, it is expected that the center of the positive charge in a unit cell will not overlap with that of the negative charge in the same unit cell, leading to the appearance of the spontaneous polarization. Thin films of Li-doped ZnO with different compositions (Zn_1-xLi_xO_y, x=0.075, 0.1, 0.125 and 0.15) have been prepared on heavily doped Si substrates by a pulsed laser deposition technique. In the films with x=0.1 and x=0.125, ferroelectric P–E hysteresis loops were successfully observed. The remanent polarization and the coercive field of Zn_0.9Li_0.1O_y and Zn_0.875Li_0.125O_y were (0.193 C/cm², 4.8 kV/cm) and (0.255 C/cm², 4.89 kV/cm), respectively. An anomalous point in the dielectric spectrum of the Li-doped ZnO ceramics is observed, showing that the ferroelectric phase transition occurs around 67 °C under 7.5 at.% Li-doped ZnO and 74 °C under 10 at.%. If the remanent polarization of this material can be further increased, it may be used as a ferroelectric material. PACS 77.80.Bh; 78.20.-e; 68.37.Ps     

Dipolar relaxation in an ultra-cold gas of magnetically trapped chromium atoms

We investigate, both theoretically and experimentally, dipolar relaxation in a gas of magnetically trapped chromium atoms. We find that the large magnetic moment of 6_B results in an event rate coefficient for dipolar relaxation processes of up to 3.2×10^-11 cm³s^-1 in a magnetic field of 44 G. We present a theoretical model based on pure dipolar coupling, which predicts dipolar relaxation rates that agree with our experimental observations. This very general approach can be applied to a large variety of dipolar gases. PACS 34.50.-s; 34.50.PI; 03.65.NK; 32.80.PJ     

Bethe-Salpeter Meson Masses Beyond Ladder Approximation

The effect of quark-gluon vertex dressing on the ground-state masses of the u/d-quark pseudoscalar, vector and axialvector mesons is considered with the Dyson-Schwinger equations. This extends the ladder-rainbow Bethe-Salpeter kernel to two-loops. To render the calculations feasible for this exploratory study, we employ a simple infrared dominant model for the gluon exchange that implements the vertex dressing. The resulting model, involving two distinct representations of the effective gluon exchange kernel, preserves both the axial-vector Ward-Takahashi identity and charge conjugation symmetry. Numerical results confirm that the pseudoscalar meson retains its Goldstone boson character. The vector meson mass, already at a very acceptable value at ladder level, receives only 30MeV of attraction from this vertex dressing. For the axial-vector states, which are about 300MeV too low in ladder approximation, the results are mixed: The 1^+– state receives 290MeV of repulsion, but the 1⁺⁺ state is lowered further by 30MeV. The exotic channels 0^–– and 1^–+ are found to have no states below 1.5GeV in this model.     

Crystalline growth of cubic (Eu, Nd):Y2O3 thin films on α -Al2O3 by pulsed laser deposition

In this paper we report on the growth of crystalline, europium- and neodymium-doped cubic yttria ((Eu,Nd):Y₂O₃) thin films on hexagonal corundum (-Al₂O₃ ) substrates using the pulsed laser deposition (PLD) technique. A KrF excimer laser was used to ablate material from ceramic (Eu, Nd):Y₂O₃ targets. The yttria films were deposited on the -Al₂O₃ (0001) substrates. X-ray diffractometry (XRD) revealed that the films grew in the Y₂O₃[111]-direction. The surface topography of the films was investigated using atomic force microscopy (AFM). PACS 81.15.Fg; 42.70.hj; 68.55.Jk     

Electroless gold deposition on silicon(100) wafer based on a seed layer of silver

This article describes a method of electroless gold deposition on a Si(100) wafer having a silver surface as seed layer. The seed layer was firstly deposited onto the surface of an etched wafer in an acidic solution of 0.005 mol/L AgNO₃+0.06 mol/LHF. The electroless gold deposition is performed by immersing the Ag-activated wafer in an electroless bath with a composition of 1.27×10^-3 mol/L[AuCl₄]^-+2.00×10^-2 mol/LNaH₂PO₂+8.32×10^-2 mol/L NH₂CH₂CH₂NH₂ (pH = 9.0–9.5). The bath temperature is 50–70 °C. The morphology of the seed layer and the gold film were characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS).PACS 82.45.Mp; 81.15.Pq; 81.10.Dn     

Diode-pumped passively Q-switched Nd : YAG laser at 1123 nm

A diode-pumped Nd:YAG laser at 1123 nm is passively Q-switched by using a low doping concentration Cr⁴⁺:YAG crystal as a saturable absorber. When pumped by a 1.5-W laser diode, the laser produces pulses of 50-ns duration with a pulse energy of as much as 15 J and a peak power of 300 W at a pulse-repetition rate of 10 kHz. PACS 42.60.Gd; 42.55.Rz; 42.55.Xi     

74% Slope efficiency from a diode-pumped Yb3+:LiNbO3:MgO laser crystal

An optimization of the laser action performance from a diode-pumped Yb³⁺-doped LiNbO₃:MgO crystal has been carried out. In this sense, efficient laser action at 1.06 m when pumping with a fiber-coupled laser diode at 980 nm has been demonstrated, achieving laser slope efficiencies as high as 74%. The influence of output mirror transmittance on both pumping threshold and laser slope efficiency has been investigated, and the parameters of relevance in laser dynamics (emission cross section and optical losses) have been determined. Under the experimental conditions leading to maximum slope efficiency, the pump power at threshold was 300mW, and the pump-to-laser conversion efficiency was 40%. PACS 42.55.Xi; 42.55.Rz; 42.60.Lh     

Electroless deposition of Ag on Pd-activated TiN/p-Si(100) substrate

Nano-thick Ag films were electrolessly deposited on TiN/p-Si(100) substrates. The substrates were prepared by sputtering TiN on p-Si(100) wafers. An activation process of the substrates was performed by immersing the substrates in a solution of 0.0019 moLL^-1PdCl₂+0.45 moLL^-1HF+8.7 moLL^-1aceticacid+0.036 moLL^-1 HCl so as to obtain the Pd seed layer. The general composition of the electroless Ag bath was 0.0032 moLL^-1AgNO₃+2.24 moLL^-1NH₃+0.56 moLL^-1aceticacid+0.1 moLL^-1 NH₂NH₂ at pH 10.2. The morphologies of the Pd seed layer and the Ag films were characterized by atomic force microscopy (AFM). The effect of the Pd activation on electroless Ag deposition was tested by open circuit potential with time technology (OCP-t). For comparison, the morphology of the films deposited by electrochemical deposition on the substrates was also studied by AFM. PACS 82.45.Mp; 81.15.Pq; 81.10.Dn     

A sensitive non-destructive method for measuring the Nd doping concentration in Nd : YAG with high spatial resolution

This paper reports on an experimental method for measuring in Nd:YAG the Nd doping concentration (C) with high sensitivity (0.01 at.%Nd) and high spatial resolution (50 m). The method is based on the measurement of the fluorescence lifetime _f of the upper Nd laser level. Additional parameters required to determine C are the intrinsic fluorescence lifetime ₀ and the quenching parameter Q. The measured values of _f, ₀ (256.47±0.14 s) and Q (4.45±0.40×10²⁰ cm^-3) allow us to calculate the Nd concentration C with an absolute accuracy of 0.1 at.%Nd. By using this method C is measured at the outer surfaces of standard laser rods and at the faces of boule slices (with diameters of up to 50 mm). The obtained results demonstrate a detection sensitivity of 0.01 at.%Nd. PACS 42.70.Hj; 81.70.Fy     

Unusual Behavior of Nanocrystalline Strontium Oxide Toward Hydrogen Sulfide

The thermodynamically favored reaction of solid strontium oxide with gaseous hydrogen sulfide is kinetically enhanced to a large degree by the use of higher surface area nanocrystalline SrO in the form of brush-like collections of metal oxide fibers. An unusual feature is that the reaction SrO + H₂S SrS + H₂O proceeds stoichiometrically at room temperature, but at higher temperatures the reaction efficiency goes down, apparently due to rapid temperature induced crystal growth of the nanocrystalline SrO. The samples studied vary in crystallite size from 20 to 27nm, while average particle size (nanocrystal aggregates) varies in the following order; aerogel prepared SrO (100nm) 相似文献   

The Q-switched Nd : YAG and Yb : YAG microchip lasers optimization and comparative analysis

The microchip lasers based on the neodymium or the ytterbium doped yttrium-aluminium garnet crystal and Q-sw itched by the Cr⁴⁺:YAG film are considered. The optimal (maximizing of energy) values of the pumping beam radius, the absorber parameters (the thickness and tetravalent chromium ion concentration), and the output mirror reflectivity are determined. The possibility of higher values of energy in the Yb:YAG laser pulse, in comparison with a more traditional Nd:YAG laser, is also substantiated. PACS 42.60.Gd