The effect of lattice order on localized phonons in Pb-In by superconductive tunneling

Localized phonon modes in quench-condensed Pb_.9In_.1 films, annealed at several temperatures up to 300 K, were studied by the method of superconductive tunneling. No localized modes could be seen in very disordered films. Structure from such modes first appeared as the crystallite grains size increased. Work supported by the Swedish Natural Science Research Council.     

Superconductivity of vapour quenched beryllium and beryllium-based alloys

The properties of Be films, quench-condensed upon a³He cooled substrate, have been investigated by resistance and tunneling measurements. The superconducting transition temperature,T _c , of Be films increased with thickness and a thick film limit of 9.95 K could be estimated. Alloying with Al or Pb decreasedT _c. The ratios between energy gaps andT _c 's indicated that Be is a weak coupling superconductor, and no phonon induced structure could be traced in tunneling curves neither in pure Be nor in the Be based alloys. Resistance change during annealing as well as superconducting data indicated that the vapour quenched Be films were amorphous as deposited.     

Martensitic transformation and magnetocaloric properties of Sn doping Mn-Ni-Ga alloys

The effects of Sn addition on phase transformation behavior and magnetocaloric properties of Mn₅₀Ni₂₅Ga_25−xSn_x (x=0, 0.1, 0.5, 1 and 2 at%) alloys were investigated in this work. The results show that the addition of Sn reduces the structural transformation temperatures. It is found that the second phase exists in the austenite matrix of the as-casted alloys at room temperature. After being annealed at 1073 K for 48 h, the precipitates totally soluted into the matrix. Magnetization measurements indicate that the saturation magnetizations of the alloys increase significantly with increase in Sn contents. In addition, the ΔM/ΔS obviously increases with increase in the Sn contents, implying the higher efficiency shift of the martensitic transformation temperature under the magnetic field.     

Effects of rapid thermal annealing on structural, magnetic and optical properties of Ni-doped ZnO thin films

XPS depth profiles were used to investigate the effects of rapid thermal annealing under varying conditions on the structural, magnetic and optical properties of Ni-doped ZnO thin films. Oxidization of metallic Ni from its metallic state to two-valence oxidation state occurred in the film annealed in air at 600 °C, while reduction of Ni²⁺ from its two-valence oxidation state to metallic state occurred in the film annealed in Ar at 600 and 800 °C. In addition, there appeared to be significant diffusion of Ni from the bottom to the top surface of the film during annealing in Ar at 800 °C. Both as-deposited and annealed thin films displayed obvious room temperature ferromagnetism (RTFM) which was from metallic Ni, Ni²⁺ or both with two distinct mechanisms. Furthermore, a significant improvement in saturation magnetization (M_s) in the films was observed after annealing in air (M_s = 0.036 μ_B/Ni) or Ar (M_s = 0.033 μ_B/Ni) at 600 °C compared to that in as-deposited film (M_s = 0.017 μ_B/Ni). An even higher M_s value was observed in the film annealed in Ar at 800 °C (M_s = 0.055 μ_B/Ni) compared to that at 600 °C mainly due to the diffusion of Ni. The ultraviolet emission of the Ni-doped ZnO thin film was restored during annealing in Ar at 800 °C, which was also attributed to the diffusion of Ni.     

Raman scattering for lead telluride-based thin film structures

For single-crystal epitaxial lead telluride films, Raman spectra obtained under conditions in which the intensity of incident radiation is minimized in order to suppress photo-initiated oxidative process are presented. The spectra were measured with an InVia Renishaw spectrometer at an exciting radiation wavelength of 514.5 nm and in-line focusing of a 20-μW beam. These measuring conditions allowed us for the first time to experimentally observe a large set of peaks for lead telluride, the positions of which were in line with the theoretical values of harmonics and combinatorial PbTe phonon modes. In order to demonstrate the possibilities of the methodology used, the picture of phonon modes for single-crystal and polycrystalline films of the Pb_{1 ? x} Eu _x Te (0.05 ? x ? 0.10) solution was additionally considered.     

Localized phonons and lattice order transformations in thallium based alloys by superconductive tunneling

Forced solutions of Tl plus 10 at.% of Na, Zn, Ag, Cd, or Sn and of Tl plus 6, 8, and 10 at.% In have been produced by vapour quenching upon a substrate cooled to 0.3 K. The lattice order of these, and similar pure Tl films, could be increased by annealing. The degree of order was mapped by changes in resistivity and in the phonon spectrum as studied by electron tunneling. As for lead based alloys, the stability of metastable disordered phases seems to be governed by the impurity melting temperature. Structure in superconductive tunneling curves, caused by localized phonon modes, was seen for In but not for the other impurities.     

Effects of Pb addition and heat treatment on optical properties of thermally evaporated Ge1−xSe2Pbx thin films

Thin chalcogenide films of Ge_1−xSe₂Pb_x (x=0, 0.2, 0.4, 0.6 and 0.8) have been prepared by the thermal evaporation technique, from previously synthesized bulk samples. The X-ray diffraction showed the amorphous nature for the as-deposited films and the partially crystalline for the annealed films. The optical constants (the refractive index, n, and absorption index k) were determined for as-deposited and annealed Ge_1−xSe₂Pb_x films of different thicknesses by using spectrophotometeric measurements of the transmittance and reflectance at normal incidence in the spectral range 200-2500 nm. The obtained values of both n and k were found to be independent of the film thickness. The optical absorption edges are described using both the Urbach rule and the indirect transition. In transparent region, the spectral dependences of refractive index were interpreted in the frame of a single oscillator model.     

The influence of substrate temperature and annealing on the properties of pulsed laser-deposited YIG films on fused quartz substrate

Yttrium iron garnet (YIG) thin films were deposited on fused quartz substrate at different substrate temperatures (T_s) varying from room temperature (RT) to 850 °C using pulsed laser deposition (PLD) technique. All the films in the as-deposited state were X-ray amorphous and non-magnetic at RT. The film deposited at RT after annealing at temperatures T_a?700 °C showed both X-ray peaks and the magnetic order. The films deposited at higher T_s (500–850 °C) and then annealed at 700 °C resulted in better-quality films with higher 4πM_s value. The highest value of magnetization was for the sample deposited at 850 °C and annealed at 700 °C, which is 68% of the bulk 4πM_s value.     

Ultrasonic attenuation of surface acoustic waves in a thin film of superconducting Nb3Sn

The attenuation of 660 MHz surface acoustic waves propagating in a thin film of Nb₃Sn 5000 Å thick has been measured as a function of temperature from 4.2 K to 16 K. The A 15 Nb₃Sn, electron-beam codeposited on YZ lithium niobate and annealed at 700°C, was studied using 5.1 μm wavelength interdigital electrodes. The film revealed a transition temperature of 14.2 ± 0.1 K and using the BCS theory, an energy gap 2Δ(0) = 3.5 k_BT_c.     

Phonon-plasmon interaction in tunneling GaAs/AlAs superlattices

The phonon-plasmon interaction in tunneling GaAs _n /AlAs _m superlattices (m=5and 6≥n≥0.6 monolayers) was studied by Raman scattering spectroscopy. The interaction of optical phonons localized in GaAs and AlAs layers with quasi-three-dimensional plasmons strengthens as the thickness of GaAs quantum wells decreases and the electronic states in the superlattices become delocalized due to tunneling. It is assumed that the plasmons also interact with the TO-like phonon modes localized in quantum islands or in thin ruffled layers.     

Structural and magnetic properties of the Dy1−xThxFe3 system and some compounds of the form M0·1Th0·9Fe3

The structural and magnetic properties of the pseudobinary Dy_1?xTh_xFe₃ system, crystallizing in PuNi₃ type structure, have been investigated. For x<0·4 the magnetization vs temperature behavior can be understood on a ferrimagnetic coupling between the dysprosium and iron sublattices. For X=0·6 to 0·9 the magnetization vs temperature data show a marked transition at temperatures above 100°K. Lattice constants indicate a discontinuity in the lattice parameter c between X=0·6 and 0·5. Similar anomalies in the M vs T behavior were observed in M_0·1Th_0·9Fe₃ (where M=Sc, Y, Pr, Lu) compounds. These results can be explained on the basis of Friedel's model of transition metal d-bands.     

带隙可调的Al，Mg掺杂ZnO薄膜的制备

利用射频磁控溅射（RF-MS）方法,固定Al₂O₃掺杂量2 wt%,Mg掺杂量分别为1 wt%,3 wt%和5 wt%,在玻璃基底上制备了Al掺杂和Al,Mg共掺杂的ZnO薄膜,在500 ℃空气中退火2 h后,测量并比较了它们的光学和电学性质．结果表明,Al,Mg共掺杂的ZnO薄膜结晶质量良好,具有ZnO纤锌矿结构,具有较强的（002）面衍射峰,表明薄膜晶体沿c轴优先生长;与Al掺杂ZnO薄膜相比蓝端光透射率增加,1 wt%和3 wt% Mg掺杂薄 关键词： 射频磁控溅射 ZnO薄膜 Al Mg共掺杂     

Electrical conduction mechanism in amorphous Se80In20−xPbx films

DC conductivity measurements on thin films of a-Se₈₀In_20−xPb_x (where x=0, 2, 6 and 10) are reported in the temperature range 200–400 K. The density of states near the Fermi level is calculated using the DC conductivity (Mott parameters). The conduction in the low-temperature region is found to be due to variable range hopping while that in the high-temperature region is due to thermally assisted tunneling of the carriers in the localized states near the band edge.     

Influence of Si-N interlayer on the microstructure and magnetic properties of γ′-Fe4N films

The (γ′-Fe₄N/Si-N)_n (n: number of layers) multilayer films and γ′-Fe₄N single layer film synthesized on Si (1 0 0) substrates by direct current magnetron sputtering were annealed at different temperatures. The structures and magnetic properties of as-deposited films and films annealed at different temperatures were characterized using X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. The results showed that the insertion of Si-N layer had a significant influence on the structures and magnetic properties of γ′-Fe₄N film. Without the addition of Si-N lamination, the iron nitride γ′-Fe₄N tended to transform to α-Fe when annealed at the temperatures over 300 °C. However, the phase transition from γ′-Fe₄N to ?-Fe₃N occurred at annealing temperature of 300 °C for the multilayer films. Furthermore, with increasing annealing temperature up to 400 °C or above, ?-Fe₃N transformed back into γ′-Fe₄N. The magnetic investigations indicated that coercivity of magnetic phase γ′-Fe₄N for as-deposited films decreased from 152 Oe (for single layer) to 57.23 Oe with increasing n up to 30. For the annealed multilayer films, the coercivity values decreased with increasing annealing temperature, except that the film annealed at 300 °C due to the appearance of phase ?-Fe₃N.     

Zur Widerstandsanomalie von Legierungen bei tiefen Temperaturen

Dilute alloys of Cu-Fe, Au-Fe, Zn-Mn, and Ag with V, Cr, Mn, Fe, Co are produced by simultaneous evaporation of both components on a substrate at 77 °K. By this method one succeeds in solving all systems, especially Cu alloys with high Fe concentration, which alloys normally show precipitations after cooling from the molten state. For these alloys we observe resistance minima up to 150 °K. Besides this, Cu-Fe shows a resistance maximum which depends on concentration. For Au-Fe and Ag-Mn we measure resistance anomalies which are even bigger for quenched films than for annealed films and bulk material. Apparently the lattice defects have an influence on the resistance anomaly. The increase of the resistance with decreasing temperature can be described by the functionρ _s /ρ _s0 =f(T/T _k ) for all systems. The result does not agree with the theories basing on Kondo's model. Here is tried an explanation by means of spin-orbit interaction. This interaction results in a temperature dependent cross-section for a molecule consisting of a magnetic impurity and a lattice defect.     

Room temperature ferromagnetism of amorphous MgO films prepared by pulsed laser deposition

Amorphous MgO thin films were prepared by pulsed laser deposition (PLD) under various oxygen pressures. The structural, magnetic, and optical properties of the films were investigated. All as-deposited samples exhibit room temperature ferromagnetism, which depend strongly on oxygen pressure. It is found that the saturation magnetization (M _s) initially increases with the oxygen pressure, the maximum M _s of 8.57 emu/cm³ is obtained for the MgO film deposited under an oxygen pressure of 2 mTorr. However, the M _s significantly reduces at higher oxygen pressures. Further X-ray photoelectron spectroscopy and photoluminescence demonstrate that the long-range magnetic order in amorphous MgO films can be attributed to the nonstoichiometry effect and the presence of Mg vacancies.     

Dielectric properties of continuous composition spreaded MgO-Ta2O5 thin films

The dielectric properties of MgO-Ta₂O₅ continuous composition spread (CCS) thin films were investigated. The MgO-Ta₂O₅ CCS thin films were deposited on Pt/Ti/SiO₂/Si substrates by off-Axis RF magnetron sputtering system, and then the films were annealed at 350 °C with rapid thermal annealing system in vacuum. The dielectric constant and loss of MgO-Ta₂O₅ CCS thin films were plotted via 1500 micron-step measuring. The specific point of Ta₂O₅-MgO CCS thin film (post annealed at 350 °C) showing superior dielectric properties of high dielectric constant (k ∼ 28) and low dielectric loss (tan δ < 0⋅004) at 1 MHz were found in the area of 3-5 mm apart from Ta₂O₅ side on the substrate. The cation's composition of thin film was Mg:Ta = 0.4:2 at%.     

Theory of lattice softening and spin-susceptibility in A15-compounds

The one-dimensional model of A15-compounds is used to calculate phonon frequencies Ω_λ (q) from temperature dependent screening properties of the electron system. The interrelationship between the magnetic susceptibility χ(q) and Ω_λ (q) is derived and both quantities are studied in the longwavelength limit ¦q¦=0 and for ¦q¦=2 ·k _itF. Numerical values are obtained for V₃Si and Nb₃Sn.     

Superconducting thin films of MxMo6S8 type

Thin films of M_xMo₆S₈, where M=Pb, Sn, Sn-Al and Cu, known as the Chevrel phases have been prepared by d.c. getter sputtering method and the optimal conditions of their preparation have been determined. The transition temperatures reached: 10.16, 13.66, 11.74 and 12.86 K for thin films with M=Cu, Sn, Sn-Al and Pb respectively. The highest critical fields H_c²(0) of 428 kG were obtained for Pb compounds.     

Annealing effect on the structural and optical properties of a Cd1−xZnxS thin film for photovoltaic applications

Herein is a report of a study on a Cd_1−xZn_xS thin film grown on an ITO substrate using a chemical bath deposition technique. The as-deposited films were annealed in air at 400 °C for 30 min. The composition, surface morphology and structural properties of the as-deposited and annealed Cd_1−xZn_xS thin films were studied using EDX, SEM and X-ray diffraction techniques. The annealed films have been observed to possess a crystalline nature with a hexagonal structure. The optical absorption spectra were recorded within the range of 350-800 nm. The band gap of the as-deposited thin films varied from 2.46 to 2.62 eV, whereas in the annealed film these varied from 2.42 to 2.59 eV. The decreased band gap of the films after annealing was due to the improved crystalline nature of the material.