Electrical and Optical Properties of GaSe Thin Films

The structure, electrical transport, and optical properties of GaSe films fabricated by means of radio-frequency (RF) magnetron sputtering in Ar were investigated. The as-sputtered GaSe films were amorphous, and their optical energy gap Eg are 1.9～2.6 eV. The effect of the synthesis conditions on the optical and electrical properties of the GaSe films has also been studied     

Thermoelectric and Magnetothermoelectric Properties of In-doped Nano-ZnO Thin Films Prepared by RF Magnetron Sputtering

Nano In-doped ZnO (IZO) films were deposited on glass substrates by RF magnetron sputtering from a powder target (2at% In) at different substrate temperatures. The thermoelectric and magnetothermoelectric properties of the IZO films were investigated. It shows that the prepared IZO films are c-axis oriented, the grain size is about 22–29 nm, and both the thermoeletromotive force (thermo-emf) and the magneto thermo-emf change linearly with temperature difference, implying that a striking thermoelectric (Seebeck) effect and magnetothermoelectric effect can be apparently observed in IZO films. The thermo-emf is negative, the Seebeck coefficient is about −57, −32, −40 and −66 μV/K for samples deposited at the substrate temperature of room temperature, 100, 200, 300°C, respectively. The power factor is (3.11–5.89)×10⁻⁵ W/K² m for our thin films. The absolute value of the magnetothermo-emf is smaller than the thermo-emf without a magnetic field, showing that the magnetic field has a negative effect on the Seebeck coefficient, which can be explained by the magnetoresistive effect substantially.     

Peculiarities of the Structure and Properties of Thin PZT Films with Strongly Nonuniform Depth–Composition Profiles

Technical Physics Letters - Two-layer thin films of lead zirconate titanate (PZT) with lead content in the layers differing by 20% were deposited by RF magnetron sputtering at variable working gas...     

Properties of Sol–Gel Derived Thin Organoalkylenesiloxane Films

We have prepared film-forming solutions for the growth of dense and porous thin organoalkylenesiloxane (OAS) films based on copolymers of methyltrimethoxysilane and 1,2-bis(trimethoxysilyl)ethane (BTMSE) by a sol–gel process. The chemical composition and microstructure of the OAS films have been studied by IR spectroscopy and spectral ellipsometry in relation to the mole fraction of BTMSE and the water: methoxy groups ratio in solution. The results demonstrate that partial substitution of ethylene bridges for silicon–oxygen bonds in OAS leads to distortion of the regular ladder-like structure characteristic of polymethylsilsesquioxane films and the presence of residual silanol groups, which causes an increase in the dielectric permittivity k of the matrix material. The relative porosity in porous OAS films produced via evaporationinduced self-assembly has been shown to be determined by not only the amount of surfactant added but also the presence of a sufficient amount of silanol groups, participating in the attachment of surfactant molecules, in the matrix copolymer solution. In this connection, an important factor determining the structure of the OAS matrix and its pore structure is control over the amount of water involved in the cohydrolysis process. It has been shown that the samples with a relative porosity of 38% prepared from a film-forming solution containing 47 mol % BTMSE (m = 0.7) and 30 wt % surfactant have k ≈ 2.3 and are potentially attractive materials for use as insulators in integrated circuits.     

Properties of TiO2 Thin Films Prepared by Magnetron Sputtering

With rapid progressive application of TiO2 thin films,magnetron sputtering becomes a very interesting method to prepare such multi-functional thin films.This paper focuses on influences of various deposition processes and deposition rate on the structures and properties of TiO2 thin films.Anatase,rtile or amorphous TiO2 films with various crystalline structures and different photocatalytic,optical and electrical properties can be produced by varying sputtering gases,substrate temperature,annealing process,deposition rate and the characteristics of magnetron sputtering.This may in turn affect the function of TiO2 films in many applications.Furthermore,TiO2-based composites films can overcome many limitations and improve the properties of TiO2 films.     

Study of the Electron–Phonon Relaxation in Thin Metal Films Using Transient Thermoreflectance Technique

Electron–phonon (e–ph) relaxation in thin metal films is an important consideration in many ultra-small and ultra-fast applications. In this work, e–ph relaxation in thin gold and aluminum films has been studied using the transient thermoreflectance technique which is demonstrated sensitive enough to study the relaxation process. The optical properties of the thin metal films are different from those of bulk metal and have been measured. Based on confirmation of the measurements, the effects of metal type, film thickness, and interface on e–ph relaxation have been experimentally studied. The thermoreflectance traces of gold and aluminum films have been compared. The results show that the e–ph relaxation and the effect of electron and lattice temperatures on the thermoreflectance of gold and aluminum are quite different. The e–ph relaxation is independent of film thickness and interface.     

Glass-to-Rubber Transition of Polymer Thin Films and Their Surface Dynamical Properties

Glass-to-rubber transition temperature, Tg' of polystyrene(PS) (Mw=500K, Mw/Mn=1.03)thin films (thickness, d= 100 to 2000 A) deposited on Si with native oxide was determined by variable angle spectroscopic ellipsometry(VASE. We observed that the Tg of the polymer films decreased monotonically as the film thickness was decreased. It had previously been proposed that this was due to a highly mobile surface rubbery layer that existed even well below Tg' We used atomic force microscopic(AFM)adhesion measurement as a direct probe to investigate the surface dynamical properties of the PS samples and a thin film ofpoly(tert-butyl acrylate) (PtBA) (Mw= 148K, Mw/Mn=17, and Tg bullk=50℃). By comparing the AFM results and those obtained from shear modulus measurements of a bulk sample, we found no enhancement in the molecular relaxation at the free surface of these samples.     

Colossal Magnetoresistance Properties of La0.83Sr0.17MnO3 Thin Films Grown by MOCVD on Lucalox Substrate

The magnetoresistance (MR) of polycrystalline La_0.83Sr_0.17MnO₃ thin films have been studied in high pulsed magnetic fields up to 38 T in the temperature range 100–300 K. The lucalox substrates were used to obtain polycrystalline structures with naturally formed grain boundaries (GBs) and crystallites whose dimensions were determined by film deposition temperature. It was found that the MR value is highest in the films having smallest crystallites. The main behaviour of high-field MR was analysed using modified Mott’s hopping model assuming that the GBs might be ferromagnetic with a Curie temperature T _C being reduced in comparison with that of the crystallites interior.     

Control of the Properties of Thin‐Film Systems with the Use of Pulsed Photon Treatment

We have developed a radically new technological process of making very largescale integrated circuits, which has no analogs and is based on the use of fast heat treatments for forming gettering layers, silicon oxidation, annealing of iondoped layers, fusion of phosphoro and borophosphorosilicate glasses, forming silicides, and increasing the thermostability of aluminum metallization.     

Magnetic Properties of Nanometer-Scale NiZnCu Ferrite Thin Films Fabricated by Spray-Spin-Heating-Coating Method

A new nanometer-scale ferrite thin film with excellent high-frequency characteristics has been developed by the spray-spin-heating-coating method. The effects of the ion synthesis mechanism, chemical stoichiometry, fabrication method, and doping content on the magnetic properties and microstructure of the thin films have been analyzed. The films formed between 75℃ and 90℃ by spray-spin-heating-coating methods was discovered with fine grain size of about 21 nm, high saturation magnetization (4πMs) of about 6.5 kGs, coercivity of about 9.8 Oe, as well as initial permeability of about 14.0. These films can be widely used in radio-frequency integrated circuit devices.     

“Thermal Prism” Method for Measuring Thermophysical Properties of Thin Films

Theoretical principles underlying the photothermal method for measuring the thickness and thermal properties of a thin film located between two optical elements (“sandwich”) are analyzed. The method is based on the irradiation of the assembly by repetitive pulse laser radiation. Radiation is absorbed in the film and causes heating of the optical elements by heat conduction. The element is monitored by a narrow beam of a second low-power laser propagating through the heated region. The beam is deflected due to the spatial variation of the refractive index, and the magnitude of the deflection angle as a function of time contains the relaxation and “wave” components. It is shown that the phase of the “wave” component depends on the thickness and thermophysical properties of the film. The thermophysical properties of the film can be determined, provided that the analogous properties of the optical element are measured previously or otherwise known, by comparing experimentally measured values of the phase shift with theoretical values obtained from the analytical solution of the non-stationary two-dimensional heat conduction equation.     

Infrared Reflectivity Spectra of Manganite Thin Films Grown on Different Substrates

We have measured the reflectivity infrared (IR) spectra of R_1−x Ca _x MnO₃ (R = La, Pr) manganite thin films grown on different substrates (SrTiO₃ (STO), LaAlO₃ (LAO) and SrLaGaO₄ (SLGO)) manganites over a wide frequency (50–5000 cm⁻¹) range. In the Far IR (FIR) region the substrates dominate over the manganite spectrum. However, the previously observed infrared active modes or mode pairs could be identified. In the mid-IR (MIR) region, a characteristic insulating gap at ∼700 cm⁻¹ is always present for all thin film studied, which shows substrate and thickness dependence.     

Preparation and Photochromic Properties of Hybrid Thin Films Based on Heteropolyoxometallate and Polyacrylamide

A series of photochromic hybrid films were prepared through entrapping Dawson type tungsten heteropolyoxomet-allates(P2W18O62^6-) and molybdenum heteropolyoxometallate(P2Mo18O62^6-) into polyacrylamide matrix.FTIR results showed that the Dawson geometry of heteropolyoxometallates in still preserved inside the composites and strong coulombic interaction is built between heteropolyoxometallates and polyacrylamide via hydrogen bonding.Ir radiated with ultraviolet light ,the transparent films change from colorless to blue and show reversible photochromism.The bleaching process occurs when the films are in contact with air or O2 in the dark.The molybdenum heteropolyoxometallate hybrid film has higher photochromic efficiency and slower bleaching reaction than tungsten heteropolyoxometallate hybrid film.ESR results indicated that polyacrylamide is a hydrogen donor and the photoreduced process is in accordance with the radical mechanism.     

Effect of Reaction Temperature and Time on the Structural Properties of Cu（In,Ga）Se2 Thin Films Deposited by Sequential Elemental Layer Technique

Thin films of copper indium gallium selenide Cu（In,Ga）Se2 （CIGS） were prepared by sequential elemental layer deposition in vacuum at room temperature. The as-deposited films were heated in vacuum for compound formation, and were studied at temperature as high as 1250℃ for the first time. These films were concurrently studied for their structural properties by X-ray diffraction （XRD） technique. The XRD analyses include phase transition studies, grain size variation and microstrain measurements with the reaction temperature and time.It has been observed that there are three distinct regions of variation in all these parameters. These regions belong to three temperature regimes： 〈450℃, 450-950℃, and 〉950℃. It is also seen that the compound formation starts at 250℃, with ternary phases appearing at 350℃ or above. Whereas, there is another phase shift at 950℃ without any preference to the quaternary compound.     

Microstructure and Mechanical Properties of Tic/NiCrMo Cermets Produced by Liquid Sintering Technique

The effect of M additions on the microstructure and mechanical properties of TiC-based cermet produced by li oquid sintering method of powder metallurgy was investigated. The Mo content was varied between 0 and 0.8 wt.%, in 0.2wt.% increments. These flaws drastically decreased with increasing Mo content. As in conventionally produced materials, Mo was found preferentially on the carbide phase. Mo-rich regions due to incomplete dissolution of large Mo agglomerates were observed.     

Effect of the Surface Modification of Synthetic Diamond with Nickel or Tungsten on the Properties of Copper–Diamond Composites

Tungsten- and nickel-containing coatings have been produced on the surface of synthetic diamond crystals by rotary chemical vapor deposition (RCVD) using tungsten hexacarbonyl, W(CO)₆, and nickelocene, Ni(C₅H₅)₂, as gaseous precursors. The thickness, composition, and morphology of the coatings have been shown to depend on the RCVD process duration and reactant concentrations in the vapor phase. The synthetic diamond microcrystals with tungsten- and nickel-containing coatings have been used to produce copper–diamond heat-conducting composites. Powder mixtures containing 50 vol % diamond with a particle size of 50, 100, or 200 μm have been consolidated by spark plasma sintering or hot pressing. It has been shown that the highest relative density (97%) and thermal conductivity (340 W/(m K)) are offered by the composites produced by spark plasma sintering using tungsten carbide-coated 50-μm diamond crystals.     

Quantum Size Effects in the Growth, Coarsening, and Properties of Ultra-thin Metal Films and Related Nanostructures

This review addresses the quantum mechanical nature of the formation and stability of ultrathin metal films. The competition between quantum confinement, charge spilling effects, and Friedel oscillations determines whether an atomically smooth metal film will be marginally, critically, or magically stable or totally unstable against roughening. Pb(111) films represent a special case, not only because of strong quantum oscillations in the stability of two-dimensional thin films but also because of the exceptionally fast coarsening of Pb nanoclusters. The latter appears to be due to the combined effects of size quantization and the existence of a unique mass exchange medium in the form of an unusually dense and highly dynamic wetting layer. The consequences of size quantization on the physical and chemical properties of the films are profound, some of which will be highlighted in this review.     

Effect of Vacuum and O2 Annealing Treatments on Structural and Magnetic Properties of La0.5Ca0.5MnO3 Thin Films

La_0.5Ca_0.5MnO₃ films with a nominal thickness of 80 nm were epitaxially grown on (001) SrTiO₃ and SrLaAlO₄ substrates by the pulsed laser deposition technique. The magnetic moment of the films was observed to depend strongly on the oxygen stoichiometry, tuned by heat treatments in vacuum and O₂ environments. A distinctly larger out-of-plane lattice parameter was measured for the vacuum-annealed films due to transformation of some Mn⁴⁺ ions to Mn³⁺. Both the variations in the magnetic moment and out-of-plane lattice parameter during vacuum annealing can be recovered by subsequent heat treatments in O₂ environment. In this study, it is shown that the enhancement of the magnetic moment via O₂ annealing is considerably less prominent than the respective improvement obtained by the application of compressive epitaxial strain.     

Effect of Melt Processing Programme on Microstructure and Properties of YBCO Thick Films

The screen printing technique was used in the fabrication of YBa₂Cu₃O_7−σ (YBCO) superconducting thick films on yttria stabilised zirconia (YSZ) substrates. Different slow cooling rates were used in the preparation of YBCO thick films after fast cooling from the melt processing temperature. The effects of the melt processing programme on texturing, microstructure and superconducting properties of the melt processed YBCO films were studied. Slow cooling rates between 1005 and 990 °C were effective in increasing the interaction of viscous molten with reduced film/substrate, and hence a relatively large grain size has been obtained. Moreover, different c-axis texturing ratios and grain morphologies were observed.