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CdGa₂S₄ was prepared in powder form by reacting CdS and Ga₂S₃. The powder had a tetragonal crystal structure with lattice parameters, a = 0.559 ± 0.005 nm, c = 1.008 ± 0.009 nm and c/a = 1.803. CdGa₂S₄ films deposited by thermal evaporation of the powder were noncrystalline. After annealing, the CdGa₂S₄ thin films contain crystals with the tetragonal crystal structure. The optical constants (the refractive index n, the absorption index k and the absorption coefficient α) were determined for CdGa₂S₄ thin films in the thickness range 170–452 nm. It was found that both n and k are independent of the film thickness and both are slightly different as deposited and annealed films. The refractive index shows anomalous dispersion in the spectral range 300–700 nm. The high frequency dielectric constant ε_∞ was determined for the as-deposited and after being annealed films. It was found that ε_∞ = 5.12 and 5.52 for the as-deposited and after being annealed films respectively. Graphical representations of (αhν)^r = f(hν) yield three linear parts, indicating the existence of two indirect and one direct allowed transitions. The values of , and for CdGa₂S₄ for the as-deposited and annealed films are presented.

There has been recent renewed interest in electrocapillary and electrowetting phenomena given its potential for microfluidic actuation and manipulation. Different approaches, in which a variety of electrode configurations have been adopted, however, have dominated the developments in this field. These different approaches have given rise to rich and varied behavior, which has often led to some overlap and confusion in the literature. In this article, we delineate the different observations and elucidate the relationship between these phenomena by re-stressing classical concepts and examining their limitations. Particular emphasis is placed on the distinction between static and spontaneous electrowetting. In the former, a static change in the liquid–solid macroscopic contact angle results when a dielectric film-coated planar plate electrode is employed. In the latter, a spontaneous thin fron-t-running electrowetting film is pulled out ahead of the macroscopic drop with the use of planar parallel line electrodes. This dynamically evolving electrowetting film advances much faster than the macroscopic drop itself and behaves in a self-similar manner analogous to gravity spreading films.

In this paper, we study the transmission properties of light through the Family A of Generalized Thue–Morse [FAGTM(n)] aperiodic multilayers and find that for the normal incidence of light there exist three kinds of cases for propagation matrices and corresponding transmission coefficients: (1) when n is even, the former are two-circular and the latter are constant; (2) when n = 1, the former and the latter are all constant; (3) when n is odd but does not equal to 1, the former are all diagonal except the 1st-generation system. The two nonzero elements are countdowns for each other and decrease or improve rapidly with the increase of both the generation number l and the parameter n. The latter are constant when l≤2 and tend to be zero when l≥3. The analytic results are confirmed by numerical simulations.

A heteroepitaxial growth model of the ZnO film on sapphire(0001) is calculated by using a plane wave ultrasoft pseudo-potential method based on the density functional theory. A strong chemical adsorption on the sapphire(0001) is observed. It is found that interfacial atoms have different diffusivity at 400°C, 600°C and 800°C. The temperature has a decisive effect on the surface and interface structures of ZnO/α-Al₂O₃(0001) and on the growth mode of ZnO thin films. In the whole process of the adsorption and growth of ZnO, the diffusivity of O atoms is higher than that of Zn, and the interlayer diffusion has an important impact on growth of the thin films. There are two growth modes of ZnO on sapphire(0001), which is further demonstrated by theoretical calculation. It can be observed from the calculation that the vacancies of Zn where the atomic layer is near to the α-Al₂O₃(0001) surface is more than that of O atoms.

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This letter deals with the experimental observation of oscillations in the infrared reflectance from Nb ultra-thin films deposited on α-type SiO₂ substrates. P-polarized reflectance (R_p) measurements are made using a tunable p-polarized CO₂ waveguide laser using wavelengths between 9.2 and 10.4 μm. Several Nb/SiO₂ quantum wells were specially made by the RF sputtering technique. Tailored thicknesses run between 5.5 and 55 Å. Because of the strong influence from the chosen substrate, IR reflectivity was fitted to the optical response of our metal-substrate system by using the three-oscillator model and numerical calculations on the basis of the local field calculation for a single metallic quantum well. Although quantum size effects are well studied in semiconductor compounds, there are only a few studies of this effect in metallic films where the present investigation has its most important contribution.

We provide an overview of the background and recent developments in the study of the morphology evolution of thin film growth. In particular, complex non-local growth effects, including the shadowing effect and the re-emission effect, have been recently shown to significantly alter an evolving growth front. The physical principles behind these non-local effects are discussed, along with techniques used by researchers in the field to model such growth.

Oscillations in the infrared reflectance from metallic ultrathin films are described as consequence of quantum size effects. In this contribution, we present experimental evidence of such oscillations for Nb ultrathin films deposited on α-type SiO₂ substrates. Also, it is shown how substrates influence the size effects and the amplitude but not the period of oscillations. Because of the strong influence from the chosen substrate due to absorption, IR reflectivity was fitted to the optical response of our metal-substrate and bare-substrate system by using the three-oscillator model and numerical calculations on the basis of the local field calculation for a single metallic quantum well. Although quantum size effects are well studied in semiconductor compounds, there are few studies of this effect in metallic films where the present investigation has its most important contribution. Measurements for p-polarized reflectance (R_p) are made using a tunable p-polarized CO₂ waveguide laser using wavelengths from the p-branch (9.4 to 9.7 μm) and R-branch (10.0 to 10.4 μm). Nb/SiO₂ ultrathin films were assembled by a conventional RF sputtering technique and tailored thicknesses were deposited from 5.5 to 55 Å.

Two series models were developed in order to investigate the gas sensitivity of 3d transition metal-doped zinc oxide (ZnO) materials. Software based on a discrete variation method (DVM) within the framework of density functional theory was used to calculate the electronic structures of the models. It was possible to determine gas sensitivity using the calculated results, from which a relationship between electronic properties and gas sensitivity was formed. The results showed that doping the transition metals greatly affected the gas sensitivity of ZnO-based materials. The main effect was attributed to the change in carrier concentration. On the contrary, the doping of transition metals had a negligible effect on the mobility of ZnO-based materials. Titanium or iron doped-ZnO is thus expected to have the best gas sensitivity of all of the 3d transition metal-doped ZnO materials.

In this paper, we propose a deviation model and consider the transmission property of Thue–Morse (TM) multilayers with deviations. It is found that at the central wavelength for very simple systems, the transmission coefficients (TCs) have nothing to do with the deviation of a machine, but when a multilayer system becomes more complex, one should use the most precise machine in order to make the system possess the designed value of TC. However, if superlattices become more complicated, one may choose a machine with a suitable relative error, but not the most accurate machine, to manufacture a perfect system. Additionally, after the number of layers exceeds some critical value, the very sophisticated optical superlattices could only be manufactured by very precise machines. The results would be useful for designing and manufacturing thin films of optical superlattices.

The temperature dependence of photoinduced anisotropy in the photoconductivity of As₂Se₃ and Sb₂S₃ thin films was investigated, in the interval between -50 and 70°C. Our results demonstrate that for both As₂Se₃ and Sb₂S₃ thin films, the anisotropy percentage falls with increasing temperature. We surmise that the aligning effect of the linearly polarized light was diluted with increasing temperature, because the latter induces similar mechanisms to those induced by polarized light, but in an isotropic fashion.

Recent research of physical properties of materials have shown that low-dimensional systems have more emphasized characteristics than bulk ones, due to quantum size effects. Superconductive films with higher critical parameters than the bulk ones are especially interesting. The basic characteristic of dispersion law of electrons in superconductive films is the presence of energy gaps. The gap size depends strongly on film thickness. Thermodynamic behavior of this system is strongly influenced by gap presence. Electron contribution in specific heat and entropy of superconductive thin film were analyzed on the basis of electron dispersion law in long-wave approximation, as well as their behavior in low temperature (T<T_C). It has been shown that both of them linearly depend on temperature, similarly as in bulk structures, but with different slope coefficient (film heat capacity is lower and entropy is higher than in the bulk at the same temperature). Due to poor heat (as well as electric) conducting properties, films are better superconductors (which is experimentally proved). Films are also less ordered systems and closer to the equilibrium state. The explanation of high temperature superconductivity can be found by studying spatially-bounded systems.

Molecular electronics is a new, exciting and interdisciplinary field of research. The main concern of the subject is to exploit the organic materials in electronic and optoelectronic devices. On the other hand, the Langmuir–Blodgett (LB) film deposition technique is one of the best among few methods used to manipulate materials at the molecular level. In this article, the LB film preparation technique is discussed briefly with an emphasis on its application towards molecular electronics.

TiO₂ thin films have been deposited on glass and indium tin oxide (ITO) coated glass substrates by sol–gel technique. The influence of annealing temperature on the structural, morphological and optical properties has been examined. X-ray diffraction (XRD) results reveal the amorphous nature of the as-deposited film whereas the annealed films are found to be in the crystalline anatase phase. The surface morphology of the films at different annealing temperatures has been examined by atomic force microscopy (AFM). The in situ surface morphology of the as-deposited and annealed TiO₂ films has also been examined by optical polaromicrograph (OPM). TiO₂ films infatuated different structural and surface features with variation of annealing temperature. The optical studies on these films suggest their possible usage in sun-shielding applications.

Vanadium oxide thin films were grown on glass substrates using spray pyrolysis technique. The effects of substrate temperature, vanadium concentration in the initial solution and the solution spray rate on the nanostructural and the electrochromic properties of deposited films are investigated. Characterization and the electrochromic measurements were carried out using X-ray diffraction, scanning electron microscopy and cyclic voltammogram. XRD patterns showed that the prepared films have polycrystalline structure and are mostly mixed phases of orthorhombic α-V₂O₅ along with minor β-V₂O₅ and V₄O₉ tetragonal structures. The preferred orientation of the deposited films was found to be along [101] plane. The cyclic voltammogram results obtained for different samples showed that only the films with 0.2 M solution concentration, 5 ml/min solution spray rate and 450°C substrate temperature exhibit two-step electrochromic properties. The results show a correlation between cycle voltammogram, morphology and resistance of the films.

Electron subsystem of ultrathin films was analyzed using Green's function method including quantum size effect and effect of boundaries on Hamiltonian parameters. We have calculated basic physical properties of electrons in crystalline films: energy spectra, possible states, space distribution of electrons and the position of Fermi level, which enabled the complete insight into the thermodynamic or conducting characteristics of observed film-structure. The comparison with crystal bulk have shown that electronic properties of the materials are strongly influenced by both the sample dimensions and boundary conditions. The numerical calculations performed for very thin crystalline metallic-like films show that localized states and spatial distribution of the (quasi)free electrons might be manipulated by varying the surface parameters which is significant for operation of devices based on thin films.

In this paper, structural and optical properties of Ga–In–Se (GIS) thin films deposited by thermal evaporation technique have been investigated. The effect of annealing was also studied for samples annealed at temperatures between 300°C and 500°C. X-ray diffraction, energy dispersive X-ray analysis and scanning electron microscopy have been used for structural characterization. It was reported that increase of annealing temperature results with better crystallization and chemical composition of the films were almost same. Optical properties of the films were studied by transmission measurements in the wavelength range of 320–1100 nm. The direct bandgap transitions with energies in the range of 1.52 eV and 1.65 eV were revealed for the investigated GIS films. Photon energy dependence of absorption coefficient showed that there exist three distinct transition regions for films annealed at 400°C and 500°C. The quasicubic model was applied for these transitions to calculate crystal-field splitting and spin-orbit splitting energy values.

In this paper, α-Mn₂O₃ thin films were fabricated by plasma-assisted molecular beam epitaxy on SrTiO₃ and Nb:SrTiO₃, respectively. The grown samples showed room temperature ferromagnetism (RFM) properties. All the experimental results manifested that the RFM properties in undoped thin films were induced by oxygen vacancies formed during the growth process. Even more, the ferromagnetism of thin films grown on Nb:SrTiO₃ were enhanced, and these results confirmed the fact that oxygen vacancies induced ferromagnetism. That is to say, more oxygen vacancies result the more unpaired electrons induced prominent abnormal spin causing ferromagnetism.

The technique of X-ray photoelectron spectroscopy has been used to investigate the chemical reactivity at the metal/CuO interfaces. Thin films of the metallic overlayer (0.5 nm, 1.0 nm and 2.0 nm thickness) were deposited on copper oxide substrates at room temperature. In situ characterization of the interfaces has been performed. The 2p core level regions of the metals have been investigated. The spectral features show considerable reactivity at the interfaces. The core level peaks of the metal are observed to be shifted to the high BE energy side with the appearance of satellites. The spectral data confirm the formation of the metallic oxide at the interface. The satellite structure in the copper region is observed to disappear and the spectral features are found to approach those of elemental copper. The room temperature deposition of the metal on copper oxide therefore results in the reduction of copper oxide to elemental copper followed by the oxidation of the metal. The interface is found to consist of a mixture of metal oxide and elemental copper. The 2.0 nm samples were annealed. These samples show the diffusion of copper oxide through the overlayer. The metal reacts with this diffusing oxide to form metallic oxide. The interface is found to consist of a mixture of unreacted metal, the metal oxide, and elemental copper. The amount of the unreacted metal varied between 0% and 40% and can be controlled by the processing conditions. The investigation shows room temperature chemical reactivity at the metal/CuO interface and provides a new method of preparing sub-nano-oxide films.

Present communication reports the LPG and NH₃ sensing properties of Co₃O₄ films prepared on throughly cleaned stainless steel (SS) and copper (CU) substrates by using DC electrochemical deposition method followed by air annealing at 350°C/2 h. The resultant films are characterized by using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The LPG and NH₃ gas sensing properties of these films are measured at room temperature (RT) by using static gas sensing system at different concentrations of test gas ranging from ~ 25 ppm to 350 ppm. The XRD and Raman spectroscopy studies clearly indicated the formation of pure cubic spinel Co₃O₄ in all films. The LPG and NH₃ gas sensing properties of films showed (i) the increase in sensitivity factor (S.F.) with gas concentrations and (ii) more sensibility to LPG as compared to NH₃ gas. In case of NH₃ gas (conc. ~ 150 ppm) and LPG gas (conc. ~ 60 ppm) sensing, the maximum S.F. = 270 and 258 are found for the films deposited on CU substrates, respectively. For all films, the response time (3–5 min.) is found to be much higher than the recovery time (30–50 sec). For all films, the response and recovery time are found to be higher for LPG as compared to NH₃ gas. Further, repeatability–reproducibility in gas sensing properties is clearly noted by analysis of data for number of cycles recorded for all films from different set of depositions.