Showing papers in "Thin Solid Films in 1996"

XPS and X-ray diffraction studies of aluminum-doped zinc oxide transparent conducting films

Abstract: Aluminum-doped zinc oxide transparent conducting films are prepared by spray pyrolysis at different dopant concentrations. These films are subsequently characterized by X-ray diffractometric and X-ray photoelectron spectroscopic (XPS) techniques. The results are compared with those obtained from pure zinc oxide films prepared under identical conditions. X-ray diffraction measurements show an increase in lattice parameters (c and a) for aluminum-doped films while their ratio remains the same. This study also indicates that within the XPS detection limit the films are chemically identical to pure zinc oxide. However, a difference in the core-electron line shape of the Zn 2 p 3 2 photoelectron peaks is predicted. An asymmetry in Zn 2 p 3 2 photoelectron peaks has been observed for aluminium-doped films. The asymmetry parameters evaluated from core-electron line-shape analysis yield a value of the order of 0.04±0.01. The value is found to lie between those obtained for pure zinc oxide and has been attributed to the presence of excess zinc in the films.

Sol—gel preparation and photoelectrochemical properties of TiO2 films containing Au and Ag metal particles

Abstract: TiO 2 film electrodes with a TiO 2 overlayer containing dispersed Au or Ag metal particles were prepared by the sol-gel method, and the effect of the metal particles on the photoelectrochemical properties of the TiO 2 electrodes were investigated. An increase in the anodic photocurrent in the visible region was observed for both the Au and Ag particle dispersed electrodes, which was thought to result from the surface plasma resonance of the metal particles. The introduction of Au metal particles, however, reduced the anodic photocurrent in the ultraviolet region, resulting in a decrease of the anodic photocurrent under the illumination of xenon lamp light. On the other hand, for the Ag particle dispersed electrodes, the anodic photocurrent in the ultraviolet region increased and then decreased with an increasing amount of Ag particles. These effects of the dispersed metal particles on the photoelectrochemical properties of the TiO 2 electrodes were explained on the basis of the band models.

Sol-gel synthesis of ZnO thin films

Abstract: Transparent and crackfree thin films of ZnO have been deposited on fused silica, soda glass, silicon wafers and KBr single crystals using the sol-gel technique. A sol has been prepared by reacting zinc acetate and ethylene glycol and dissolving the resultant transparent brittle solid in dry n-propanol. A proton acceptor like triethyl amine was added to assist hydrolysis of zinc acetate. The resulting solution was readily gelled on addition of water. Films were spin cast on polished substrates, gelled in humid air and pyrolysed at 450 °C to get polycrystalline ZnO thin films. The films were characterized using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and UV-Vis absorption spectroscopy.

Deformation and fracture in microlaminates

Abstract: The utility of microlaminates in engineering applications depends ultimately on their strength and toughness. While the properties of monolithic films and coatings can be controlled through crystal structure and microstructure, the properties of microlaminates are a sensitive function of the interfaces. It is the large number of interfaces in a microlaminate that determines the unique behavior of this special type of composite. This review begins with a property-based definition of a microlaminate. The mechanisms by which microlaminates deform plastically are reviewed and evaluated in the context of data on metal-metal, metal-intermetallic, metal-ceramic and ceramic-ceramic systems. It is evident that in addition to layer geometry, the layer microstructure plays a major role in determining the operative deformation mechanism. The fracture processes in a microlaminate are examined in the context of the layer strength, microstructure, defects and crack-tip-dislocation processes. High toughnesses in microlaminate materials can be attained through a combination of mechanisms, and their effectiveness depends critically on the ability to affect the magnitude and shape of the stress field at the tip of the crack. The study of deformation and fracture in microlaminates is still a relatively young field in materials science. However, while our understanding of these processes is still quite incomplete, it is improving rapidly with advances in experiment, theory and modeling capability.

Porous silicon multilayer optical waveguides

Abstract: Optical waveguiding is demonstrated in porous silicon multilayers. Depth variations in porosity, and therefore refractive index, are achieved by switching between high and low current densities during the anodic etch process. Planar waveguiding has been demonstrated at λ = 1.28 μm. The wavelength range has been extended to the visible (λ = 0.6328 μm) by oxidising the samples to produce layered porous oxide structures. Two-dimensional strip-loaded waveguides have been produced, for both the visible and infrared, by etching into each top layer through a pre-deposited photolithographically-defined mask.

Assembly of polyelectrolyte multilayer films by consecutively alternating adsorption of polynucleotides and polycations

Abstract: Multilayers films of nucleic acids (DNA, polyuridylic and polyadenylic acids) and polycations (polyallylamine, polyethylenimine, polylysine and polyarginine) were fabricated by consecutive adsorption of anionic and cationic polyelectrolytes. The film growth process was controlled by X-ray reflectivity and UV spectroscopy. The penetration of DNA-specific dye was examined for DNA-polyallylamine self-assembled films.

Preparation and characterization of spray pyrolysed cobalt oxide thin films

Abstract: Cobalt oxide thin films were prepared by the spray pyrolysis method on amorphous glass substrates kept at 300 °C. The films formed were uniform, pin-hole free, and strongly adherent to the substrates. The X-ray diffraction studies revealed that the films consist of Co 3 O 4 oxide phase. The optical and the electrical properties of the film were also studied.

Influence of substrates on the elastic reaction of films for the microindentation tests

Abstract: The influence of substrates on the elastic reaction of a thin film was investigated using a load- and depth-sensing microhardness tester. For the investigation silicon oxide films were produced in a radio frequency (r.f.) plasma with hexamethyldisilane and oxygen, on silicon wafers and glass ribbons simultaneously for the first set of smaples and on silicon wafers but with various film thickness for the second set. The Young's moduli of the silicon oxide films were meausured to be different for the different substrates for the same thickness of film. The Young's moduli of the silicon oxide films decreased for the same substrate with increasing film thickness to approach the Young's modulus of a silicon oxide film. The elastic deformation was considered for the normal point load to a flat quasi-infinite surface using an elementary theory of elasticity under the assumption of perfect adhesion between the film and substrate. The Young's modulus of the film was recalculated using the equation derived, considering the elastic deformation of the normal point load to a flat quasi-infinite surface. T he recalculated film Young's modulus of 67 ± 1.5 GPa was nearly independent of the film thickness, which is comparable with the modulus value of thermally grown silicon oxide.

A new method for fabricating transparent barrier layers

Abstract: The Polymer Multi-Layer (PML) process for the vacuum flash evaporation of acrylic monomers has been combined with conventional oxide sputtering and evaporation processes to produce multilayer barrier coatings in a vacuum web coating process. Polymer/oxide/polymer layers have been deposited on 2 mil polyester substrates. For a 1 μm polymer layer over the substrate, followed by a 255 A Al2O3 layer capped by a 0.24 μm polymer layer, O2 permeation rates were below 0.0155 cc m−2 (24 h)−1 and H2O permeation rates were less than 0.0155 g m−2 (24 h)−1. These exceptional permeation rates are believed to result from the substrate smoothing effect of the initial polymer layer. This layer eliminates substrate defects, prior to deposition of the oxide layer, and permits the oxide layer to grow with a minimum of pinholes. The capping polymer layer protects the oxide film during wind-up and subsequent handling.

Oxidation of TiN, ZrN, TiZrN, CrN, TiCrN and TiN/CrN multilayer hard coatings reactively sputtered at low temperature

Abstract: All the coatings and multilayer structures were deposited in a Sputron plasma-beam-sputtering apparatus at a temperature below 150 °C on polished alumina substrates (Ra= 25 nm) and polished tool steel discs. The coatings were annealed in an oxygen flow at temperatures in the range 500–850 °C. The oxidation kinetics of these coatings were studied by means of the weight gain as a function of the oxidation time at each temperature. On the same coatings, continuous in situ electrical resistivity measurements were taken and these indicate grain boundary oxidation. The composition and the depth profiles of the oxidation products formed were investigated using AES and XPS combined with sputter profiling. The oxide layers were found to grow according to a parabolic diffusion law with activation energies of 1.04, 1.89, 1.92, 2.37,2.91 and 3.98 eV for Ti0.63Zr0.37N, TiN, CrN, ZrN, TiN/CrN and Cr0.72Ti0.28N, respectively.

Transparent conducting ZnxCd1−xO thin films prepared by the sol-gel process

Abstract: Thin films of zinc oxide, cadmium oxide, and their compounds have been deposited by the sol-gel process. The ZnO and CdO films are found to have different crystallographic structures and their compounds are found to be simple mixtures of the two different crystallographic strutures for the constituent materials. The electrical resistivity of the compounds, ZnxCd1−xO thin films decreases as the composition x decreases, so that pure CdO thin films have the lowest electrical resistivity of 3×10−3 Ωcm. Although the optical transmittance and bandgap of the ZnxCd1−xO films also decrease as the value of x decreases, all the films prepared in this study have a fairly high transmittance reproducibly in the visible spectral range at room temperature. The electrical resistivity of the films is found to have significant dependence on the post-deposition annealing environments. This dependence is more pronounced for the films which contain higher percentages of Zn among all the ZnxCd1−xO films prepared in this study. The dependence of the electrical resistivity on the aluminium impurity concentration in the ZnxCd1−xO films is also examined.

Synthesis and optelectronic characterization of gallium doped zinc oxide transparent electrodes

Abstract: In this work we report on pulsed laser deposition of gallium-doped zinc oxide (ZnO:Ga) transparent-conducting thin films grown on glass at different substrate temperatures. A widening in the optical bandgap and a good gallium-doping efficiency were observed in the films when the substrate temperature was raised from 150 °C to 300 °C, as determined from optical and electrical measurements. X-ray diffraction measurements revealed that the films grow preferentially oriented in the [002] crystallographic direction of the ZnO grains. The crystallinity of the films was also found to be strongly dependent on the substrate deposition temperature. The ZnO:Ga transparent films had excellent transmittance (85%) in the visible spectrum and a low electrical resistivity value (7 × 10 −4 Ω cm) in 200 nm thickness samples deposited on glass by laser ablation at 300 °C.

Molecular film assembly via layer-by-layer adsorption of oppositely charged macromolecules (linear polymer, protein and clay) and concanavalin A and glycogen.

Abstract: Protein multilayer assemblies were prepared by two different methods: (1) alternate adsorption of oppositely charged polyions; (2) alternate adsorption with specific enzyme/substrate interaction. The formation of alternate outermost layers (opposite charge or opposite specificity) at each adsorption cycle is the key point of the procedure. Three modes of polyion film assembly were demonstrated: (a) alternation of linear polyanions and polycations; (b) insertion of charged particles in the multilayer at every other step (twelve different globular proteins were assembled alternating with Na (poly (styrenesulfonate), poly(ethyleneimine)) or Cl (poly(diallyldimethylammonium))); (c) alternation of polyions and preformed charged plates: delaminated montmorillonite clay. Specific interaction was obtained between consecutive layers of glycogen and concanavalin A. Concanavalin A possesses four binding sites for its ligand D-glucose and allows the binding of glycogen (branched poly (glucose)) layers on both sides of the protein.

Correlation between the density of TiO2 films and their properties

Abstract: Stress, density and refractive index of approximate 100 nm thick titania films are determined for layers deposited on fused silica substrates by reactive evaporation (RE), reactive ion plating (IP), plasma impulse chemical vapour deposition (PICVD) and spin coating (SC). Relative densities (ϱfilmϱana) vary between 0.7 and 1.0 with respect to the crystal phase of anatase (ϱana = 3.84 g cm−3). The refractive index depends linearly on density. Film stress is tensile at low densities and compressive for layers with densities of the order of anatase. A strong correlation between stress and density is found to be independent from the deposition conditions and the crystal structure of the as-deposited films. The phase transition from amorphous to anatase caused by annealing induces an increase in stress. The film density is correlated to the crystallization temperature, the size of stress increase during crystallization and the grain size.

Electrochemical deposition of MoS2 thin films by reduction of tetrathiomolybdate

Abstract: Molybdenum sulphide was cathodically electrodeposited from aqueous solutions of sodium tetrathiomolybdate. The as-deposited films were X-ray amorphous with a composition, measured by microprobe analysis, close to MoS 2 . Annealing these films in Ar resulted in highly-textured films of MoS 2 with the van der Waals planes parallel to the substrate. A small expansion in the c spacing of the annealed films was explained by the presence of oxygen in the crystals. A direct bandgap of 1.78 eV was found for the annealed films.

WNx diffusion barriers between Si and Cu

Abstract: The barrier properties of W, W2N and WN layers to prevent intermixing of Cu wiring with the Si substrate were investigated. W, W2N and WN barrier layers 25 nm thick were found to prevent intermixing after annealing at 650, 790 and 500°C for 30 min, respectively. W2N, which showed the best barrier property, had a polycrystalline structure with disordered grain boundaries, and Cu diffusion in W2N was concluded to be controlled by grain boundaries of the W2N layer based on the diffusional analysis of Cu in W2N.

Electroluminescent zinc sulphide devices produced by sol-gel processing

Abstract: Zinc sulphide thin film electroluminescent devices doped with Mn or Tb have been produced on p-type Si substrates using a process in which doped zinc oxide films are deposited by a sol-gel drain coating method from a solution of zinc acetate containing a manganese or terbium dopant. The films are then converted to ZnS by heating them in an atmosphere containing hydrogen sulphide which replaces the oxygyn with sulphur. The composition, crystalline structure and optical properties of films have shown that complete conversion from the oxide to the sulphide takes place. The luminescent characteristics of the devices so produced have been measured as a function of the doping concentrations, film thickness, insulator thickness and driving voltage and frequency. It has been found that yellow or green luminescence can be obtained using Mn or Tb doping respectively.

Effect of normal load on microscale friction measurements

Abstract: Friction force microscopy (FFM) was used to study microscale friction between a sharp tip and various samples. Effect of normal load and tip material on the coefficient of friction has been studied. Friction force as a function of normal load of virgin silicon with a thin film of native oxide and dry-oxidized SiO2 coating showed two distinct slopes. The coefficient of friction in the low load region of less than about 15 mN is lower than that in the high load region. The critical load at which the coefficient of friction starts to increase corresponds to the specimen hardness. Ploughing at high loads is believed to be responsible for high values of the coefficient of friction. The coefficient of friction of polished natural diamond remains virtually independent of normal load because no ploughing occurs. The coefficient of friction on a macroscale is higher than that on a microscale for comparable contact stresses. When measured for the small apparent area of contact and very small loads used in microscale measurements, the indentation hardness and modulus of elasticity on a microscale are higher than that at the macroscale. This reduces the degree of wear at the microscale. In addition, small apparent areas of contact in microscale measurements reduces the number of particles trapped at the interface and thus minimizes the ploughing contribution to the friction force. Based on this study, it is concluded that measured values of the coefficient of friction on a microscale are a strong function of normal load and the apparent area of contact. Ultralow values of the coefficient of friction and near-zero wear can be achieved with microscale components at very light loads in the absence of significant ploughing.

Monolayer thickness in atomic layer deposition

Abstract: The growth rate in atomic layer deposition (ALD) or epitaxy (ALE) is usually saturated to a constant level when appropriate operation conditions are attained. The layer thickness deposited in one cycle is limited by adsorption. A simple molecular description for chemisorption and surface reactions is suggested and shows that both reaction steps have an effect on the growth rate. A model is developed for the calculation of the growth rate from the geometry of the reactant molecules and the density of the adsorption sites on the surface. The results are compared with experimental values of binary oxide, sulphide and fluoride thin films. In most cases, a surface configuration is found that gives the observed growth rate.

A novel capacitor technology based on porous silicon

Abstract: A capacitor based on an electrochemically etched macroporous silicon substrate and a layered dielectric (ONO) is presented. This solid-state technology allows us to realize values of specific capacitance which so far could only be reached by electrolytic capacitors. The dependence of the capacitance on temperature, frequency, applied bias and time of operation is found to be negligible. Due to a low series resistance and a operating temperature of at least 200 °C the device withstands high a.c. currents. Being a silicon chip, the capacitor is fully compatible with today's surface mounted device and multi-chip module technologies.

Chemical vapour deposition and characterization of gallium oxide thin films

Abstract: Gallium oxide thin films were deposited on alumina and TiO2 substrates by metal organic chemical vapour deposition using gallium trishexafluoroacetylacetonate (Ga(hfac)3) as precursor in the presence of oxygen. The depositions were carried out at 470°C and 2.6 kPa leading to a growth rate of 0.7 μm h−1. As-grown films appeared black, smooth and well adherent to the substrates. X-Ray photoelectron spectroscopy (XPS) analysis revealed stoichiometric Ga2O3 with a low carbon content (less than 5%) and almost undetectable fluorine. As-deposited Ga2O3 films were X-ray amorphous, but the onset of a crystallization process was evident after annealing in dry air at 700 °C. Moreover, after thermal treatment, the films became carbon free and transparent in the visible range. The effect of annealing at different temperatures on the film structure was investigated by X-ray diffraction. A phase modification from amorphous to polycrystalline Ga2O3 was observed after thermal treatment at temperatures from 600 to 1000 °C. As shown by secondary ion mass spectrometry (SIMS) studies, Al diffusion into Ga2O3 films was detected after annealing at 1000 °C when pure Al2O3 was used as substrate; this diffusion was completely inhibited using a TiO2 film as buffer layer with a thickness of at least 4 μm.

Preparation and properties of spin-coated Nb2O5 films by the sol-gel process for electrochromic applications

Abstract: The preparation and properties of Nb2O5 coatings made by the sol-gel process were investigated. The films were deposited by spin coating on In2O3:Sn/glass and quartz substrates from a polymeric solutions of niobia derived from niobium ethoxide. The films were characterized by investigation of the stoichiometry, refractive index, optical transmission, electrochemical behavior, and the microstructure. X-ray diffraction studies showed the films to be amorphous for heat treatments below 450°C. X-ray photoelectron spectroscopy (XPS) measurement revealed the O:Nb atomic stoichiometry to be 5:2. Cyclic voltammetric measurements showed that the Nb2O5/1M LiClO4-propylene carbonate system exhibits electrochemical reversibility beyond 1 200 cycles without change in performance. In situ UV-Vis-NIR spectroelectrochemical measurement revealed that Nb2O5 films exhibit an electrochromic effect in the spectral range 300<λ<2100 nm and remain unchanged in the infrared spectral range. The change in visible transmittance was 40% for a 250 nm thick electrode. XPS spectra indicate that Nb(V) is reduced to a lower valence state Nb(IV) in a colored state with injected Li+. The bronze coloration is due to a simultaneous injection of electrons and Li+ ions into Nb2O5. The sol-gel-deposited Nb2O5 films are useful for cathodically coloring electrochromic electrodes in electrochromic devices.

Apparent interface toughness of substrate and coating couples from indentation tests

Abstract: Determination of adhesive properties of coatings is one of the most important problems for the extension of the use of coated materials. Numerous studies are devoted to the research of new tests which have to face practical as well as scientific problems. In this work, we propose to evaluate adhesion of coatings by means of an apparent interfacial toughness. The interface indentation test provides a relation between the applied load (P) and the length of the crack (a) created at the interface between the coating and the substrate. Representing this relation in bilogarithmic coordinates shows that the relation is linear and may be expressed by the equation a = αPn where the exponent n is a function of the coating thickness. When the residual stresses due to solidification of the coating are removed by an appropriate annealing treatment, the straight lines corresponding to different thicknesses intersect at the same point. We have shown earlier that this point corresponds to the half diagonal of the indent and then to a limit (ac) for which no crack is formed by indentation. Therefore this point (critical point PC) may be considered as a criterion representative of the adhesive properties of the coating on its substrate. In order to give a usable value of these adhesive properties, we suggest to represent adhesion by an apparent interfacial toughness based on the critical load Pc. As the interfacial test is used to create and propagate a crack, some authors have proposed in a recent past to transpose the principle of indentation tests used to determine toughness of brittle materials. In this study, we expressed an apparent interfacial toughness in function of the critical point (Pc, ac), apparent elastic modulus E1 and apparent hardness H1 of the interface: Kca = 0.015Pcac3/2EH1 As the indentation is performed at the interface between the coating and the substrate, hardnesses and elastic properties of both the substrate and the coating are concerned by the indentation process. The (E/H)1 ratio had necessarily to be dependent on these properties. Considering the plastic deformations as well as the indentation diagonals into the substrate and into the coating, we may define the following relation: EH11/2 = EHS1/21 + HSHR1/2 + EHR1/21 + HRHS1/2 The critical load is representative of adhesive properties of the coating, then the apparent interfacial toughness should vary in the same way. We have verified this point on a chromium carbide coating thermally sprayed on various metallic substrates and on a stellite coating on an austenitic steel. The proposed model gives toughness values in good accordance with the critical indentation loads necessary to initiate a crack at the interface between the coating and its substrate. As a consequence, this apparent interfacial toughness may be considered as a criterion to represent adhesion of a coating on a substrate.

Structurally stable composite PdAg alloy membranes: Introduction of a diffusion barrier

Abstract: This work investigates the improvement of the structural stability of PdAg alloy membranes by introduction of a diffusion barrier. Asymmetric PdAg films were deposited on porous stainless steel (SS) substrate by electroless plating. The formation of these alloys was achieved by annealing the as-deposited membranes at temperatures higher than Tamman temperatures of the alloy components in a hydrogen atmosphere. The composite PdAg membranes were characterized using XRD and Auger electron depth profiling. The atomic interdiffusion of silver and palladium resulted in PdAg alloys in an fcc structure. To improve the structural stability of PdAg alloy/SS membranes, an ultrathin intermediate layer of titanium nitride being 0.1 μm thick was introduced as a diffusion barrier between PdAg and the SS substrate. The Auger electron depth profiling analysis indicated that the improved membranes were thermally stable at temperatures as high as 973 K, and practical for the catalytic membrane reactor use. An estimation of diffusion coefficients revealed that the presence of hydrogen in the annealing atmosphere favoured the PdAg interdiffusion and thus the formation of PdAg alloys.

Investigation of the stresses and stress intensity factors responsible for fracture of thin protective films during ultra-micro indentation tests with spherical indenters

Abstract: This paper reports on the mechanical characterization of thin hard films deposited on softer substrates using the micro-indentation technique together with spherically tipped indenters. After a short review of the deformation and fracture behavior the indentation process is simulated using a finite element analysis in order to determine the stresses responsible for the first fracture event of the film. A fracture mechanics analysis is presented that uses the weight function method to calculate the stress intensity factors K 1 and K 11 within the near surface region of the film. A fracture criterion for multiaxial loading conditions is used to calculate the stress intensity factor K Iappl . It will be shown that for films which are thin compared to the radius of the indenter first fracture should occur under a Mode-I loading condition. For the cases where the film was thick compared to the indenter radius mixed mode loading conditions prevail and the resultant fracture path is dependent on the nature of the film microstructure.

Non-destructive characterization and evaluation of thin films by laser-induced ultrasonic surface waves

Abstract: Ultrasonic surface waves induced by a pulsed laser act as high-frequency elastic oscillations propagating along the target materials surface. The velocity of these propagating waves is effected by the elasticity and density of the material. These surface waves have a unique property in that their depth of penetration in the material decreases with an increase in their frequency. At higher frequencies, the velocity of the surface waves are effected if the film or near-surface region composition differs from the substrate material. Generating surface waves using short laser pulses has allowed for non-destructive measurements to be performed over a wide frequency range. This in turn results in a spectrum of velocity frequencies which, when compared to known film and density characteristics using a fit program, can be used to characterize surface composition and thin films. This velocity spectrum can be used to determine Young's modulus, density, and thickness of the film. The ultrasonic thin film analyzer has been developed for use in industrial test laboratories and research institutes.

Fabrication and characterization of ITO thin films deposited by excimer laser evaporation

Abstract: We report the fabrication of tin-doped indium oxide (ITO) thin films by pulsed laser evaporation (PLD) without post-annealing treatment. The electrical, optical and structural properties of these films have been accurately investigated. We show that this growth method gives good quality ITO layers with high transparency (higher than 80% in the visible spectrum) and low electrical resistivity (in the order of 3 × 10−4 Ω cm). Considering the free electrons contribution in the near-infrared region, we determine the plasma frequency, the relaxation time, the high frequency dielectrical constant and the optical effective mass of the electrons in conduction band. Therefore, we establish the variation of the ITO optical complex refractive index in the wavelength range between 0.3 and 1.5 μm. Moreover, in applications on an InP solar cell, Auger profilometry shows that PLD preserves the substrate surface and, therefore, PLD is a technologically simple method providing good ITO ohmic transparent contact.

Characterization of the oxidized indium thin films with thermal oxidation

Abstract: Oxidized indium thin films on several substrates were formed by indium deposition and thermal oxidation. The oxidation was carried out in oxygen ambient at temperatures ranging from 500 to 900°C for 1 h. In the scanning electron microscopy measurements, the oxidized indium films were shown to be composed of grains with sizes of 400 to 600 nm which agglomerate subgrains with diameters of 40–60 nm. From the measurements of X-ray diffraction, X-ray photoelectron spectroscopy and Auger electron spectroscopy, it was confirmed that the oxidized indium are cubic indium oxide (In 2 O 3 ) polycrystallites. In addition, no elements other than In and O atoms were found from secondary ion mass spectroscopy measurements. A strong orange photoluminescence, peaking at 637 nm, was observed at room temperature for these films. It was assumed that a center of orange luminescence in the indium oxide films may be related to oxygen deficiencies or defects.

Crystallization of organic thin films for electroluminescent devices

Abstract: The interfacial change of a vapor-deposited tris(8-hydroxyquinoline) aluminum complex (Alq 3 ) N,N′ - diphenyl -N,N′- bis (3- methyl-phenyl ) - (1,1′- biphenyl ) -4,4′- diamine (TPD) ( Alq 3 TPD) bilayer and the surface morphology of the Alq 3 TPD bilayer and the mixed single layers of co-deposited TPD and Alq3 were characterized by fluorescence microscopy and spectroscopy, and atomic force and friction force microscopy in the range of temperature from room temperature to 80 °C under air. In this study was found enhanced suppression of the crystallization of TPD in a molecularly dispersed system such as the co-deposited Alq3-TPD mixed film in comparison with the single-component TPD film. It was also found that the crystallization of Alq3 in the interface of the bilayer or in the co-deposited single layer proceeded before the crystallization of TPD.

Electrodeposition of CuInS2 from aqueous solution (II) electrodeposition of CuInS2 film

Abstract: As the first stage for thin film preparation of copper indium disulfide (CuInS 2 ), an electrodeposition technique of thin films in the CuS system was investigated from a new viewpoint. Deposition was carried out potentiostatically on a Ti substrate from acidic aqueous solution containing CuSO 4 and Na 2 S 2 O 3 . Tartaric acid was found to be effective as a buffer for stabilizing the hydrogen ion concentration. Thin films of Cu 2 S were obtained at −0.7 V vs. Ag/AgCl with good reproducibility from a solution containing 10 mM CuSO 4 , 400 mM Na 2 S 2 O 3 and 100 mM tartaric acid. Scanning electron microscopy and energy dispersive X-ray analyses revealed that the film deposited had a crack-free surface and uniform stoichiometry of Cu 2 S. Film thickness was estimated to be 0.6−0.8×10 −6 m after 3600 s deposition. The mechanism of Cu 2 S formation was supposed to be that S 2 O 3 2− ion reduces Cu(II) ion to make complex with Cu(I) ion. Probably it is this complex that contributes to the Cu 2 S formation.