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Abstract Zirconium dioxide (ZrO 2) thin films were deposited onto glass substrates, indium tin oxide (ITO) coated glass substrates and nickel oxide (NiO) / ITO / glass structures by reactive radio frequency (RF) magnetron sputtering using a zirconium target at room temperature. The deposition power was held at 75 W and the influence of deposition pressure and film thickness on the properties of the ZrO 2 films were investigated. Optical, electrochemical and electrochemical impedance spectroscopy measurements of the ZrO 2 films were performed and the electrochromic behavior of a half-cell structure of ZrO 2 / NiO / ITO / glass was investigated in a wide spectral range. The amount of inserted/extracted charges into/from each film during bleaching/coloring process were investigated in detail. The highest coloration efficiency (24.3 cm2/C) and optical modulation (42.8%) at a wavelength of 550 nm were found for a ZrO 2 / NiO / ITO / glass structure having a ZrO 2 film with a thickness of 100 nm, deposited at 4.00 Pa. Finally, a unique design of an all solid-state electrochromic device with a configuration of ITO / NiO / wet lithiated ZrO 2 / dry lithiated tungsten oxide (WO 3) / ITO / glass was fabricated. The optical modulation of the device was 53% at 550 nm for the applied potentials of ±3 V. Highlights • Optical and electrochromic (EC) behavior of ZrO 2 were studied. • The EC behavior of a half-cell structure of ZrO 2 /NiO/ITO/glass was investigated. • An uniquely designed all-solid-state EC device was fabricated. • The large optical modulation was found to be 53% with the applied voltages of ±3 V. • The ZrO 2 film was used as Li+ ion conducting layer in the EC device. [ABSTRACT FROM AUTHOR]

Abstract Ellipsometry is an optical technique for determining properties of laminar reflecting (or transmitting) structures from the measurement of light polarization state change resulting from the light-sample interaction. In all but the simplest of cases, the measurements must be followed by data processing in which the measured data is compared to an appropriate mathematical model of the sample derived from Maxwell's equations and measurement conditions. Thus a key common problem is determining how many and which measurements to make. A single measurement in standard ellipsometry consists of one complex data point and in generalized ellipsometry, three complex data points and therefore usually more than one measurement is required. Previously we have addressed these problems using Complex Analysis in the n-k plane for homogeneous isotropic films. One of the key findings was that certain angles and wavelengths are useful and others are not. The purpose of the work here is to extend that analysis to anisotropic films. These films have a greater number of unknowns and consequently may require more measurements. The central question remains, how many measurements are needed and which specific measurements will provide sufficiently independent equations considering the unknowns. It can be that additional measurements vary to such a small degree that they are not useful considering measurement error tolerance. The work to be presented will show how to identify useful measurements based upon the anticipated, non-depolarizing sample configuration. The approach avoids making unnecessary measurements which can actually reduce the solution accuracy. Highlights • Ellipsometry solutions for anisotropic media. • High sensitivity angle-wavelength combinations. • A Priori selection of ellipsometer measurements. • Ellipsometer data analysis methods. [ABSTRACT FROM AUTHOR]

We report on the effect of added silver on the solid state dewetting behavior of copper thin films, grown by thermal evaporation. The films were annealed under different conditions, conventional furnace annealing in air and argon and rapid thermal annealing in nitrogen. Our results show that for all annealing conditions, addition of silver to copper films suppresses the dewetting when compared to pure copper films. Fully dewet silver–copper films produce roughly spherical nanoparticles, with the amount of silver controlling the particle areal density and size distribution. This provides an additional parameter for controlled synthesis of nanoparticles by a bottom–up approach. [ABSTRACT FROM AUTHOR]

In this paper, we report graphene on Ge(111) by using an electron beam evaporation under appropriate conditions in ultra high vacuum. Surface morphology, structural and electronic properties of graphene on Ge(111) substrate are investigated in detail by low energy electron diffraction, Auger electron spectroscopy, X-ray photoemission spectroscopy, Raman spectroscopy, optical microscopy, scanning electron microscopy, atomic force microscopy and scanning tunneling microscopy. We found that the crystalline quality of graphene reduces with increasing the amount of deposited carbon atoms during graphene formation at near melting temperature of the Ge substrate. [ABSTRACT FROM AUTHOR]

Structure, morphology, and optical properties of Gd implanted GaN epitaxial layers were studied for (0001), (11 − 20), and (11 − 22) orientations. The GaN layers grown by MOVPE on sapphire were subsequently implanted with 200 keV Gd + ions using fluences of 5 × 10 15 and 5 × 10 16 cm − 2 . Dopant depth profiling was accomplished by Rutherford Back-Scattering spectrometry (RBS). Structural and optical changes during subsequent annealing were characterized by RBS, Raman spectroscopy, and photoluminescence measurements. Post-implantation annealing induced a structural reorganization of GaN structure in the buried layer depending on the introduced disorder level, i.e. depending on the implantation fluence and on crystallographic orientation. The defect density depth distribution was evaluated by RBS. The surface morphology and optical properties depend on particular crystallographic orientation. [ABSTRACT FROM AUTHOR]

A simple system of epitaxial film electrodes with no additives is desirable for investigation surface reactions and anisotropic electrochemical properties of battery's active materials. In this work we demonstrate the possibility of growing epitaxially by pulsed laser deposition single orientation thin films of two phases, orthorhombic o-LiMnO 2 and monoclinic m-Li 2 MnO 3 ; the phases were and still are of great interest for developing high capacity intercalation cathodes for Li-ion batteries. Orientation of the films was controlled by selecting orientation of SrTiO 3 substrate covered coherently with a layer of SrRuO 3 to provide electrical contact for future electrochemical measurements. Different phases were formed by adjusting temperature of a substrate during deposition, 600 °C for forming m-Li 2 MnO 3 , and 700–800 °C – for o-LiMnO 2 . Detailed high-resolution scanning transmission electron microscopy of cross-sections has determined the unique orientation relationship for both phases, which can be seen as cube-on-cube of cubic and pseudo-cubic oxygen sub-lattices of SRO and Li-Mn-O phases, respectively. Lower symmetry of the Li-Mn-O phases results in formation of structural domains, which are analyzed in detail. [ABSTRACT FROM AUTHOR]

Abstract: There is currently a great interest to design and fabricate novel flexible devices for solar cell, solid-state lighting, biomedical and energy harvesting applications. Such devices require the use of electrode components. Desired electrodes must exhibit structural integrity, low electrical resistivity and, in most cases, high optical transparency in the visible range. Despite growing efforts to replace them, transparent conducting oxide layers deposited on polymer substrates are still enjoying a dominant role as the electrode component. This is because of their excellent combination of electrical and optical properties. However, their performance when they are subjected to externally-applied mechanical stresses is limited. Such performance has been extensively investigated for the case of continuous brittle oxide films on polymer substrates. However, there is relatively little work reported to date on the mechanical behavior of patterned conducting layers on compliant substrates. In this study we report on the mechanical behavior of various patterned indium tin oxide shapes and sizes on polyethylene terephthalate. Micron-sized shapes include squares, circles, and zigzag-based structures. Controlled buckling experiments are performed in-situ using an optical microscope in order to monitor critical strains and potential failure mechanisms. In addition, ITO electrical resistance changes are continuously monitored during deformation. Furthermore, ex-situ characterization of the tested surfaces using scanning electron microscopy is conducted. Higher crack onset values are observed for the smaller size patterns. Also, square-shaped patterns are found to exhibit the lowest crack onset values. SEM observations suggest cracking-driven and buckling-driven delamination during ITO tensile and compressive buckling mode respectively. In both cases, failure is observed to initiate from the pattern edges. [Copyright &y& Elsevier]

Abstract: The effect of high-energy ball milling on calcium fluoride was studied by X-ray Diffraction (XRD) Line Profile Analysis (LPA) and Solid State Nuclear Magnetic Resonance (NMR) spin–lattice relaxation. The latter technique is especially useful not only to detect the nonhomogeneous effects of the early stages of mechanical grinding, but is also sensitive to the defect structure of the ball milled powders. When supported by Solid State NMR, XRD LPA unveils fine details of the milling effects on fluorite, in terms of increasing dislocation density and progressive refinement of the crystalline size down to the nanoscale. [Copyright &y& Elsevier]

Abstract: Porous thin films deposited by glancing-angle deposition (GLAD) have found application as sensor, micro-electrical mechanical systems and microfluidic devices. However, conventional micro-fabrication techniques can damage the very properties which make GLAD films attractive for these applications. To facilitate integration of GLAD films with these processes, a capping layer may be used. Such capping layers must be as free of defects as possible to ensure that the GLAD film is well protected. Here, the cracking properties of evaporated TiO2 caps deposited on GLAD films have been investigated as a function of substrate temperature. Our films are a porous vertical post layer 2.7μm thick capped with a solid 400nm layer. This material system experiences tensile stress from two sources: thermal mismatch between the film and substrate, and intrinsic stress in the cap from Volmer–Weber coalescence. Crack properties such as crack length distribution, crack density and branch number were quantified. In general, higher substrate temperatures reduced crack density, branch number and preferentially eliminated longer cracks. The onset of crystallinity at substrate temperatures around 300°C briefly increases crack area and branch number, but a further reduction can be achieved by depositing above this temperature. Applications of films grown by GLAD requiring high-quality capping layers will benefit from this study. [ABSTRACT FROM AUTHOR]

Abstract: Electric and electro-optical properties of a smectic liquid crystal (LC) compound formed by rod-like molecules have been investigated in the thin film sandwich geometry typically used in solid-state technology. Thin (~10–30 nm) Langmuir–Blodgett (LB) films of the compound (tetradecyl homologue (n =14) of the series p-oxybenzylidene-p′-amino-2-methylbutyl(α-cyano)cinnamate) were transferred onto glasses covered with a transparent electrode and supplied with a top electrode evaporated in vacuum. In contrast to the LC bulk, thin films of the compound manifest only a solid crystalline phase throughout the whole temperature range (20–110 °C) investigated. Ferroelectric properties of the films (covering linear electro-optic effect, pyroeffect and polarization switching) have been observed in the whole temperature range studied. [Copyright &y& Elsevier]

Abstract: The synthesis of materials from Fisher''s carbene ferrocenyl of the elements chromium, molybdenum and tungsten was carried out. The Fisher''s compounds that were synthesized included the following combinations of two different metallic atoms: iron with chromium, iron with molybdenum and iron with tungsten. The molecular solids'' preparation was done in electro-synthesis cells with platinum electrodes. Thin films were prepared by vacuum thermal evaporation on quartz substrates and crystalline silicon wafers. Pellets and thin films from these compounds were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy, atomic force microscopy and ellipsometry. The powder and thin films synthesized from these materials show the same intra-molecular bonds shown by infrared spectroscopy results, suggesting that thermal evaporation does not alter these bonds in spite of the thin films being amorphous, in contrast with other bimetallic complexes where material decomposition occurs. The differences in the conductivity values of the prepared films are very small, so they may be attributed to the different metallic ions employed in each case. The tungsten complex exhibits a higher conductivity than the molybdenum and chromium complexes at room temperature. Electrical conductivity values found for thin films are higher than for pellets made of the same molecular materials. [Copyright &y& Elsevier]

Abstract: Tantalum nitride thin films were deposited by radio frequency (RF) reactive sputtering at various N2/Ar gas flow ratios and working pressures to examine the change of their electrical resistivity. From the X-ray diffraction (XRD) and four-point probe sheet resistance measurements of the TaN x films, it was found that the change of the crystalline structures of the TaN x films as a function of the N2 partial pressure caused an abrupt change of the electrical resistivity. When the hexagonal structure TaN thin films changed to an f.c.c. structure, the sheet resistance increased from 16 Ω/sq to 1396 Ω/sq. However, we were able to control the electrical resistivity of the TaN thin film in the range from 69 Ω/sq to 875 Ω/sq, with no change in crystalline structure, within a certain range of working pressures. The size of the grains in the scanning electron microscopy (SEM) images seemed to decrease with the increase of working pressure. [Copyright &y& Elsevier]

Abstract: Hybrid thin films have been deposited on silicon substrates under several conditions such as different annealing temperatures and RF power by plasma enhanced chemical vapor deposition method using single molecular precursors. The result of the FT-IR measurement showed that the plasma polymerized thin films have highly cross-linked density with increasing RF power and annealing temperature. An impedance analyzer was utilized for the measurements of I–V and C–V curves. From the electrical properties measurements, the lowest dielectric constant and best leakage constant were obtained to be 2.26 and 10−9 A/cm2 at 1 MV/cm, respectively. Also, the mechanical properties of the films were determined with nano-indentation. [Copyright &y& Elsevier]

Abstract: A new photochromic ZrO2 precursor solution was prepared using zirconium tetra-n-butoxide, 4-(phenylazo)benzoic acid and ethyleneglycol monomethylether. The density functional theory (DFT) calculation has identified that the structure of the synthesized precursor molecule changed by UV irradiation. Four types of thin films were prepared using the ZrO2 precursor solution with and without UV irradiation and applying an electric field. It was found that the surface morphology of thin films changed by applying UV irradiation to the precursor solution and an electric field. [Copyright &y& Elsevier]

Abstract: The temperature dependences of electrical conductivity, σ, and Seebeck coefficient, S, for some new pyridium monoquaternary salts derivatives, 1-(p-R-phenacyl)-4-{[(1′-ethylcarboxylate)-(3′-p-R′-phenacyl)]-7′-indolizinyl}pyridinium bromides have been studied. The film samples (d =0.08–0.28 μm) have been deposited onto glass by an immersion technique (dimethylformamide was used as a solvent). The investigated compounds behave as typical p-type polycrystalline semiconductors. The activation energy of electrical conduction ranged between 0.65 and 1.72 eV, while the ratio of charge carrier mobilities laid in the range (0.60–0.83). The model based on band gap representation is suitable in explaining the electronic transport in present compounds in the higher temperature range (385–500 K). [Copyright &y& Elsevier]

Abstract: ZnO thin films were prepared on fused silica from a single spin-coating deposition of a sol–gel prepared with anhydrous zinc acetate [Zn(C2H3O2)2], monoethanolamine [H2NC2H4OH ] and isopropanol. Crystallization annealing was performed over the range 500 to 650 °C. X-ray analysis showed that thin films were preferentially orientated along the [002] c-axis direction of the crystal. The films had a transparency of greater than 85% in the visible region for sol–gels with a zinc content of up to 0.7 M and exhibited absorption edges at ∼378 nm. The optical band-gap energy was evaluated to be 3.298–3.306 eV. Photoluminescence showed a strong emission centered at ca. 380 nm along with a broad yellow-orange emission centered at ca. 610 nm. Single step sol–gel thin film deposition in the film thickness range from 80 nm to 350 nm was demonstrated. The effect of sol–gel zinc concentration, film thickness and crystallization temperature on film microstructure, morphology and optical transparency is detailed. A process window for single spin coating deposition of c-axis oriented ZnO discussed. [Copyright &y& Elsevier]

Abstract: Transparent wide band gap indium molybdenum oxide (IMO) thin films were rf sputtered on glass substrates at room temperature. The films were studied as a function of sputtering power (ranging 40–180 W) and sputtering time (ranging 2.5–20 min). The film thickness was varied in the range 50–400 nm. The as-deposited films were characterized by their structural (XRD), morphological (AFM), electrical (Hall Effect measurements) and optical (visible-NIR spectroscopy) properties. XRD studies revealed that the films are amorphous for the sputtering power ≤100 W and the deposition time ≤5 min, and the rest are polycrystalline with a strong reflection from (222) plane showing a preferential orientation. A minimum bulk resistivity of 2.65×10−3 Ω cm and a maximum carrier concentration of 4.16×1020 cm−3 are obtained for the crystalline films sputtered at 180 W (10 min). Whereas a maximum mobility (19.5  cm2 V−1 s−1) and average visible transmittance (∼85%) are obtained for the amorphous films sputtered at 80 W and 100 W respectively for 10 min. A minimum transmittance (∼18%) was obtained for the crystalline films sputtered at 180 W (∼305 nm thick). The optical band gap was found varying between 3.75 and 3.90 eV for various sputtering parameters. The obtained results are analyzed and corroborated with the structure of the films. [Copyright &y& Elsevier]

Abstract: We report on the basic properties of amorphous/crystalline hetero-junctions (a-Si:H/c-Si), their effects on the recombination of excess carriers and its influence on the a-Si:H/c-Si hetero-junction solar cells. For that purpose we measured the gap state density distribution of thin a-Si:H layers and determined its dependence on deposition temperature and doping by an improved version of near-UV-photoelectron spectroscopy. Furthermore, the Fermi level position in the a-Si:H and the valence band offset were directly measured. In combination with interface sensitive methods such as surface photovoltage analysis and our numerical simulation program AFORS-HET, we found an optimum in wafer pretreatment, doping and deposition temperature for efficient a-Si:H/c-Si solar cells without an i-type a-Si:H buffer layer. We reached at maximum 19.8% certified efficiency by a deposition at 210 °C with an emitter doping of 2000 ppm of B2H6 on a well cleaned pyramidally structured c-Si(n) wafer. [Copyright &y& Elsevier]

Abstract: We present a method for the determination of orientation-dependent mobilities Γ eff(φ) based upon analyses of the detachment-limited coarsening/decay kinetics of equilibrium-shaped two-dimensional islands. An exact analytical expression relating the orientation-dependence of Γ eff(φ) to that of the anisotropic step energies β(φ) is derived. This provides relative values of Γ eff(φ) to within an orientation-independent scale factor that is proportional to the decay rate of the island area. Using in situ high temperature (T =1550–1700 K) low-energy electron microscopy measurements of two-dimensional TiN island coarsening/decay kinetics on TiN(111) terraces for which β(φ) values are known [Phys. Rev. B 67 (2003) 35409], we demonstrate the applicability of our analytic formulation for the determination of absolute Γ eff(φ) values. [Copyright &y& Elsevier]

Abstract: We report the low temperature noncollinear magnetic behavior of direct current (DC) sputtered FePt thin films investigated by performing DC magnetization, thermoremanence, magnetic relaxation, and electrical transport measurements down to 1.8 K. The obtained results, interestingly, indicate a transition from ferromagnetic state to a low temperature disordered state where a collective frozen magnetic state with grain moments oriented randomly occurs. The magnetic relaxation and electrical resistivity measurements at low temperature support the spin-glass like phase, which diminishes and finally disappears with an applied field of moderate strength. We interpret the observed low temperature noncollinear magnetic behavior to be due to random freezing of grain moments. [Copyright &y& Elsevier]

Abstract: Continuous fluorinated amorphous carbon (a-C:F) films doped with nitrogen (a-C:F:N) were deposited by plasma enhanced chemical vapor deposition using CF4 and C2H2 gases as precursors with the addition of N2 gas. The surface morphologies, chemical compositions, deposition rates, thermal stability and mechanical properties of these films varied with the deposition parameters, including CF4 and N2 feed gas concentrations, processing pressure, plasma power and substrate temperature. With increasing N2 feed gas concentration, the nitrogen content of the a-C:F:N films increased to about 6 at.% and contributed to higher mechanical properties. After thermal annealing, the a-C:F films with higher fluorine contents exhibited more obvious fluorine release and extensive film thickness shrinkage, whereas the a-C:F:N films with higher contents of nitrogen doping yielded less composition variations, smaller thickness shrinkages, higher mechanical properties, and conclusively better thermal stability. [Copyright &y& Elsevier]

Abstract: This paper reports the effect of niobium on the structure of titanium dioxide (TiO2) thin films deposited on glass. The results obtained indicated that the direct current (DC) co-sputtering of Ti and Nb onto glass substrates in the presence of oxygen results in the formation of Nb-doped anatase thin films with strong preferential orientation. In the concentration range between 0 and 40 at.% Nb, niobium is incorporated into the TiO2 lattice according to a substitution mechanism, entering Ti sites in the cation sub-lattice. No evidence exists for a solubility limit <40 at.% of Nb under the applied deposition conditions, however, it is not believed that an equilibrium situation prevails. Lattice charge compensation was concluded to occur by the formation of cation vacancies for samples with up to 10 at.% Nb, and by Ti3+ or Nb4+ ions for the samples with ≥15 at.% Nb, the latter in conjunction with cation vacancy compensation. [Copyright &y& Elsevier]

Abstract: The microwave dielectric properties of Ba0.6Sr0.4TiO3 1 mol% W-doped thin films deposited using pulsed laser deposition, are improved by a novel oxygen deposition profile. The thin films were deposited onto (001) MgO substrates at a temperature of 720 °C. A comparison is made between three different oxygen ambient growth conditions. These include growth at a single oxygen pressure (6.7 Pa) and growth at two oxygen pressures, one low (6.7 Pa) and one high (46.7 Pa). Films were deposited in a sequence that includes both a low to high and a high to low transition in the oxygen deposition pressure. Following deposition, all films were post-annealed in 1 atm of oxygen at 1000 °C for 6 h. The dielectric Q (defined as 1/tanδ) and the dielectric constant, ε r, were measured at room temperature, at 2 GHz, using gap capacitors fabricated on top of the dielectric films. The percent dielectric tuning (defined as (ε r(0 V)− ε r(40 V))/ ε r(0 V)×100) and figure of merit (FOM) (defined as percent dielectric tuning× Q(0 V)) were calculated. The film deposited using the two-stage growth conditions, 6.7/46.7 Pa oxygen, showed a maximum Q(0 V) value with high percent dielectric tuning and gave rise to a microwave FOM twice as large as the single stage growth condition. The improved dielectric properties are due to initial formation of a film with reduced interfacial strain, due to the formation of defects at the film/ substrate interface resulting in a high Q(0 V) value, followed by the reduction of oxygen vacancies which increases the dielectric constant and tuning. [Copyright &y& Elsevier]

Abstract: Antimony-doped tin oxide (SnO2:Sb) thin films were fabricated by an ultrasonic spray pyrolysis method. The effect of antimony doping on the structural, electrical and optical properties of tin oxide thin films were investigated. Tin(II) chloride dehydrate (SnCl2·2H2O) and antimony(III) chloride (SbCl3) were used as a host and a dopant precursor. X-ray diffraction analysis showed that the non-doped SnO2 thin film had a preferred (211) orientation, but as the Sb-doping concentration increased, a preferred (200) orientation was observed. Scanning electron microscopy studies indicated that the polyhedron-like grains observed for the non-doped SnO2 thin films became rounder and decreased in size with the Sb-doping concentration. The lowest resistivity (about 8.4×10−4 Ω·cm) was obtained for the 3 at.% Sb-doped films. Antimony-doping led to an increase in the carrier concentration and a decrease in Hall mobility. The transmittance level in the near infrared region was lowered with the Sb-doping concentration. [Copyright &y& Elsevier]

Abstract: Ion-beam assisted deposition of polycrystalline Y2O3 films using e-beam evaporation was investigated. For growth on non-crystalline substrates, low temperature growth yields randomly oriented polycrystalline material. At elevated temperature, surface energy anisotropy yields a (111) uniaxial texture. For film deposition with irradiation from an Ar ion beam, the out-of-plane texture remained (111) in orientation. The incident Ar ion beam induces an in-plane alignment of the Y2O3 films that is relatively broad. A six-fold symmetry in the out-of-plane X-ray diffraction phi-scans was observed for the (111) textured Y2O3 films, indicating a multi-variant in-plane texture and suggesting anisotropic damage along both the (110) and (100) projections. The lack of a sharp, single variant in-plane texture with ion beam irradiation is consistent with the relatively weak bond strength in Y2O3. [Copyright &y& Elsevier]

Abstract: A simple sol–gel route has been developed for the preparation of nanocrystalline photocatalytic TiO2 thin films and particles at 500 °C. The synthesis involved a novel chemistry method employing nonionic surfactant molecules as a pore directing agent along with acetic acid-based sol–gel route without direct addition of water molecules. This study investigated the effect of surfactant type and concentration on the homogeneity, morphology, light absorption, dye adsorption and degradation, and hydrophilicity of TiO2 films as well as on the structural properties of the corresponding TiO2 particles. The method resulted in the synthesis of mesoporous TiO2 material with enhanced structural and catalytic properties including high surface area, large pore volume, pore size controllability, small crystallite size, enhanced crystallinity, and active anatase crystal phase. The prepared TiO2 thin films were super-hydrophilic and possessed thermally stable spherical bicontinuous mesopore structure with highly interconnected network. Highly porous TiO2 films prepared with polyethylene glycol sorbitan monooleate surfactant exhibited four times higher photocatalytic activity for the decoloration of methylene blue dye than the nonporous control TiO2 films prepared without the surfactant. This sol–gel method modified with surfactant templates is useful in the preparation of nanostructured anatase TiO2 thin films with high photocatalytic activity and desired pore structure. [Copyright &y& Elsevier]

Abstract: Samarium-doped ceria (SDC) thin films were prepared from Sm(DPM)3 (DPM=2,2,6,6-tetramethyl-3,5-heptanedionato) and Ce(DPM)4 using the aerosol-assisted metal–organic chemical vapor deposition method. α-Al2O3 and NiO-YSZ (YSZ=Y2O3-stabilized ZrO2) disks were chosen as substrates in order to investigate the difference in the growth process on the two substrates. Single cubic structure could be obtained on either α-Al2O3 or NiO-YSZ substrates at deposition temperatures above 450 °C; the similar structure between YSZ and SDC results in matching growth compared with the deposition on α-Al2O3 substrate. A typical columnar structure could be obtained at 650 °C on α-Al2O3 substrate and a more uniform surface was produced on NiO-YSZ substrate at 500 °C. The composition of SDC film deposited at 450 °C is close to that of precursor solution (Sm:Ce=1:4), higher or lower deposition temperature will both lead to sharp deviation from this elemental ratio. The different thermal properties of Sm(DPM)3 and Ce(DPM)4 may be the key reason for the variation in composition with the increase of deposition temperature. [Copyright &y& Elsevier]

Abstract: The refractive indices of textured indium tin oxide (ITO) and zinc oxide (ZnO) thin films were measured and compared. The ITO thin film grown on glass and ZnO buffered glass substrates by sputtering showed distinct differences; the refractive index of ITO on glass was about 0.05 higher than that of ITO on ZnO buffered glass in the whole visible spectrum. The ZnO thin film grown on glass and ITO buffered glass substrates by filtered vacuum arc also showed distinct differences; the refractive index of ZnO on glass was higher than that of ZnO on ITO buffered glass in the red and green region, but lower in the blue region. The largest refractive index difference of ZnO on glass and ITO buffered glass was about 0.1 in the visible spectrum. The refractive index variation was correlated with the crystal quality, surface morphology and conductivity of the thin films. [Copyright &y& Elsevier]

Abstract: RuO2 thin films were grown on (001) LaAlO3 utilizing the pulsed laser deposition technique. Atomic force microscopy was used to check the topography of films at different growth stages. The in situ resistivity measurement was used to monitor the resistance change during and post film growth with changes of resistivity associated with the change of film growth mode. Transmission electron microscopy was used to reveal film quality and crystalline information. The layer-plus-island Stranski–Krastanov growth mode is proposed according to above results. The ambient O2 filled during growth is found to be the main oxygen source for the formed RuO2. [Copyright &y& Elsevier]

Abstract: Highly preferred oriented lead barium titanate (Pb1−x ,Ba x )TiO3 thin film, with particular emphasis on (Pb0.5,Ba0.5)TiO3, can be obtained by spin-coating on MgO (100) substrate by using the precursor sol, which was synthesized from acetylacetone chelating with titanium isopropoxide and ethylene glycol as a solvent, in the sol-gel process. Film thickness, pyrolysis temperature and heating rate were studied systemically to investigate their influences on the formation of preferred oriented thin films. The highly preferred (001)/(100) oriented thin film could be obtained by the pyrolysis of wet film at 500 °C and annealing at 600 °C at a slow heating rate of 5 °C/min. It is confirmed that the tetragonal perovskite structure of the titanate ceramic decreases with an increase of Ba content in (Pb1−x ,Ba x )TiO3. The (001)/(100) oriented films were synthesized from all compositions between x =0.2 and x =0.8, at a crystallization temperature of 600 °C. In particular, for the Ba content in the range of x =0.5∼0.6, highly preferred (001)/(100) planes were observed. [Copyright &y& Elsevier]

Abstract: TiO2 films were grown by atomic layer deposition on Mo electrodes in order to elucidate the dominating conductance mechanism and its dependence on the growth chemistry. TiCl4 and Ti(OC2H5)4 served as titanium precursors, and H2O or H2O2 as oxygen precursors. The films grown at lower temperatures were amorphous. With increasing growth temperatures the crystallization first started in the TiCl4–H2O process. The films grown in this process were clearly leakier compared to the films grown from Ti(OC2H5)4 and H2O and from Ti(OC2H5)4 and H2O2. In the Ti(OC2H5)4-based processes, the application of H2O2 instead of H2O resulted in the films with considerably lowered conductivity, although structural differences in these films were insignificant. Space–charge-limited currents were prevailing in all our amorphous Mo–TiO2–Al packages. Measurements at different temperatures suggested quite high trap densities likely due to the presence of impurities and structural disorder, while the strong differences in conductivity seemed to be due to different densities of gap states. [Copyright &y& Elsevier]

Abstract: Spectroscopic ellipsometry was used to extract the optical constants of zinc oxide (ZnO) thin films deposited on (100) silicon substrate by filtered cathodic vacuum arc technique. Three dispersion models, namely, Sellmeier dispersion model, Cauchy model and Forouhi–Bloomer model, were evaluated for determining the optical constants of ZnO thin films below the energy band gap. The study shows that the Cauchy model provides the best spectral fittings among these three models. Above the energy band gap, two ellipsometric models, namely, two-phase model and three-phase point-by-point fit, were used. This study reveals that the initial values used in the point-by-point fitting play a critical role. It also shows that the refractive index and the extinction coefficient calculated with the two-phase model can be used as the initial values for the point-by-point fitting. The spectral dependence of the refractive index and extinction coefficient obtained in this work is comparable with the data reported in the literature. In sum, a reliable methodology for determining the optical constants of ZnO thin films in the ultraviolet-visible-near infrared range (250∼1100nm) has been developed. [Copyright &y& Elsevier]

Abstract: Optoelectronic properties of Cu(In1–x Ga x )Se2 (CIGSe) have been studied by confocal microscopic photoluminescence (PL) with lateral submicron resolution. The lateral patterns of PL-yields, varying by factors of up to 10 between regimes with low and high emission, exhibit structures in the length scale of some micrometers (3–10 μm) whereas geometrical sizes of individual grains are in the 1-μm range or below. In addition to the local PL-variation, we observe that the geometrical extension of PL-patterns depend on excitation flux, that spectral PL-shapes are varying with respect to different onset energies of the low-energy wings, signalizing different local band gaps, and that low-energy PL-wings get steeper with rise in excitation flux pointing towards potential fluctuations and their respective screening by photoexcited excess carriers. [Copyright &y& Elsevier]

In this report, we propose Al2O3 and AlN films as passivation for high-voltage SiC Schottky barrier diodes. A reactive pulse plasma enhanced chemical vapour deposition method is used to form the layers. The comparison between the Schottky barrier diodes with and without passivation shows the effectiveness of Al2O3 layer on the reverse current decrease as a result of the surface states reduction. [Copyright &y& Elsevier]

The TaSiO6 films, ∼6 A˚ thick, were formed by sputter deposition of Ta onto ultrathin SiO2 substrates at 300 K, followed by annealing to 600 K in 2 Torr O2. X-ray photoelectron spectroscopy (XPS) measurements of the films yielded a Si(2p) binding energy at 102.1 eV and Ta(4f7/2) binding energy at 26.2 eV, indicative of Ta silicate formation. O(1s) spectra indicate that the film is substantially hydroxylated. Annealing the film to >900 K in ultra-high vacuum resulted in silicate decomposition to SiO2 and Ta2O5. The Ta silicate film is stable in air at 300 K. XPS data show that sputter-deposited Cu (300 K) displays conformal growth on Ta silicate surface (TaSiO6) but 3D growth on the annealed and decomposed silicate surface. Initial Cu/silicate interaction involves Cu charge donation to Ta surface sites, with Cu(I) formation and Ta reduction. The results are similar to those previously reported for air-exposed TaSiN, and indicate that Si-modified Ta barriers should maintain Cu wettability under oxidizing conditions for Cu interconnect applications. [Copyright &y& Elsevier]

Using (Poly(phenylene vinylene) (PPV)/Poly(styrene sulfonate) (PSS)) and (PPV/Poly(methacrylic acid) (PMA)) self-assembled bilayers exhibiting different hole transport properties, we investigated the competing effect on quantum efficiency of the variation of relative thicknesses of (PPV/PSS) and (PPV/PMA) bilayers in indium tin oxide (ITO)/(PPV/PSS)n/(PPV/PMA)m/Al devices with fixed 20 bilayers (i.e. n+m=20). The (PPV/PSS) bilayer is known to be better as a hole transport layer due to higher leakage current and lower quantum efficiency in comparison with the (PPV/PMA) emitting bilayers. With increasing the number of (PPV/PSS) bilayers from 0 to 20 bilayers, the quantum efficiency of the multilayer self-assembled device was at maximum with 3 bilayers of (PPV/PSS) in contact with the ITO anode and the efficiency montonically decreased upon further increase of the (PPV/PSS) bilayer above 3. In the case of the increase of (PPV/PSS) bilayer thickness by the addition of NaCl salt to the PSS solution during the layer deposition process, the quantum efficiency of the device was significantly improved and also maximized with the 3 (PPV/PSS) bilayers. The significant change on the quantum efficiency by a simple control of relative bilayer numbers is mainly attributed to the competing effects caused by the increase of hole transport (PPV/PSS) bilayer at the expense of reduced emitting (PPV/PMA) bilayer. It was also found that the enhancement of the quantum efficiency by the addition of NaCl salt to the PSS solution is mainly caused by sufficient surface coverage of the (PPV/PSS) hole transport bilayers on the ITO electrode. [Copyright &y& Elsevier]

Surface germanium oxide is often ignored in the ex situ characterization of Ge coherent islands grown on Si substrates. Therefore, the effects of the native oxide have to be justified. We thus intentionally oxidize the Ge coherent islands in air and ozone, strip the oxide layer by water, and assess the effects of native GeOx oxide layer on ex situ shape and strain measurements. We estimate that the thickness of Ge consumed due to its oxidation in air is ∼0.4 nm in domes and less than 0.4 nm in pyramids. This native oxide on the Ge islands has negligible effect on the island shape and strain measurements. Upon etching in water, domes continuously change their shape to lower aspect ratio. Thus, island aspect ratio can be tailored in a controllable fashion by water etching due to the different oxidation rate between the base and top of the island. The dependence of strain relaxation in a coherent island on aspect ratio is compared with the theoretical calculations. [Copyright &y& Elsevier]

In the present work, the catalyst Pt was evaporated onto the sol–gel WO3, WO3–SiO2 films. These films were annealed at different temperatures and their structures were characterized by infrared, visible near infrared spectroscopy and X-ray diffraction. The coloring kinetics of the films was evaluated. The results revealed that the 0.75WO3–0.25SiO2 composite films had faster coloring rates than the WO3 films. This improved behavior is attributed to the faster diffusion of atomic H resulting from the existence of more absorbed water, more pores, more phase boundaries, and more grain boundaries in the composite films. [Copyright &y& Elsevier]

AlN films, grown by nitrogen or argon ion beam-assisted pulsed laser deposition, exhibit very high stresses at a certain ion energy. These stresses are mainly caused by ion beam-induced defects. The magnitude of stress is found to depend not only on the ion energy, but also on the deposition temperature and the ion incidence angle. To explain the relation of the observed film stresses and the appropriate deposition parameters, a simple model was developed. The model takes into account the annealing of a certain fraction of the ion beam-induced point defects by thermal diffusion towards the film surface, which acts like a sink of the defect concentration. This model allows us to predict the ion energy where the point defect concentration in a film reaches a maximum in agreement with the experimental observation of the stress maximum. [Copyright &y& Elsevier]

In this paper, an extensive study of the photocurrent amplification mechanism of silicon bulk-barrier diodes (BBDs) is presented, based on simulation and experimental results. As a result of this study an analytical model is proposed. The proposed model extends previously published models and includes analytical expressions for all significant quantities of the device optoelectronic behaviour. Such quantities are barrier lowering, photocurrent, quantum efficiency and response speed as functions of the applied voltage, incident light power, light wavelength and modulation frequency, as well as a function of technological parameters. Simulation and experimental results verify the validity of the proposed analytical model, and they show that BBDs are majority carrier photodetectors with high internal photocurrent gain. Compared with common photodetectors, BBDs exhibit a very high sensitivity in the blue region of the visible spectrum. [Copyright &y& Elsevier]

Room-temperature epitaxy of indium tin oxide (ITO) thin films was achieved on Si(111) substrates with an epitaxial CeO2 ultrathin buffer using a pulsed laser deposition technique. The epitaxial CeO2 buffer layer was also grown at room temperature. Reflection high-energy electron diffraction and pole figure X-ray diffraction analyses confirmed the formation of a double heteroepitaxial structure of ITO(111)/CeO2(111)/Si(111) with the epitaxial relationship of [−110]ITO//[−110]CeO2//[1–10]Si. The junction of [ITO: 100 nm thick/CeO2: 3 nm thick/p-Si(111)] fabricated at room temperature exhibited solar cell properties. [Copyright &y& Elsevier]

The pyroelectric effect arises as a result of the change of the polarisation with temperature. Pyroelectric materials, which must have a non-centrosymmetric structure, exhibit an inherent electrical polarisation that changes when their temperature is changed. A heterogeneous monolayer system containing linear copolysiloxanes has been shown to produce a non-centrosymmetric structure in this work. Alternate layer Langmuir–Blodgett (LB) films have been fabricated using LB film deposition technique. The pyroelectric and dielectric properties of these alternate layer LB film assemblies have been measured and used to determine the pyroelectric figure of merit in the context of thermal imaging devices. [Copyright &y& Elsevier]

Different approaches to the multi-source evaporation of Cu(In,Ga)S2 for thin film solar cells have been studied. Indirect synthesis via a copper-free precursor film leads to superior transport properties but also to an inherent grading of the [Ga]/([In]+[Ga]) ratio. Solar cells prepared from these absorbers show confirmed total area conversion efficiencies up to 12.3%, exceeding the previous record for selenium-free chalcopyrite based cells. A more homogeneous gallium depth distribution and a higher absorber band gap have been achieved by modifying the preparation sequence. An efficiency of more than 10% is demonstrated for the first time with high gap chalcopyrite absorbers as required for tandem configurations. [Copyright &y& Elsevier]

Polymer mono- and multilayer films containing 5,10,15,20-tetraphenylporphyrin (TPP) moieties in various amounts were prepared by the conventional Langmuir–Blodgett (LB) technique using amphiphilic copolymers based on poly(isobutyl methacrylate). The copolymers showed similar surface pressure (π)–area (A) isotherms even for the high TPP contents, indicating that the TPP moieties are located out-of-plane of the monolayer on the air/water interface. The deposition onto solid substrates allowed one to fabricate multilayer films, in which the TPP moieties were incorporated into the polymer ultrathin films of only approximately 1 nm in thickness. The absorption dichroism revealed that the TPP moieties took a parallel orientation with a uniform distribution in the two-dimensional plane structure. [Copyright &y& Elsevier]

We have investigated the role of aluminum oxide films as barriers to thermal oxidation of Co, Ni, Fe, Ni80Fe20, Mn, Ta, Cu and Cr in air. The oxidation of the film is monitored by measuring the electrical resistance following a brief anneal in air. We find that 0.3 and 1 nm Al protect the underlying metal film against thermal oxidation in air at temperatures of a few hundred degrees above the temperature at which the unprotected metal oxidizes. These results suggest that magnetic tunnel junction samples could be annealed in air after the oxidation of Al. The expected benefits of the annealing in air would include the oxidation of any remaining metallic Al, a more uniform Al2O3 thickness, and a sharper metal/Al2O3 interface. [Copyright &y& Elsevier]

The influence of implanted Si, Mo and Ce vs. the as-received austenitic AISI 304 stainless steel has been studied after isothermal oxidation in air at 900 °C for 32 h. The oxide layer formed was characterised by means of conventional X-ray diffraction, scanning electron microscopy/energy-dispersion spectroscopy and X-ray absorption spectroscopy (XAS) techniques. The projected ranges of the implantation were calculated using the trim code. The results obtained by the most sensitive technique, XAS, show slight differences in the chemical composition of the oxide layer of the different ion-implanted samples. However, these chemical differences could determine a threshold between acceptable and non-acceptable oxidation behaviour. The evolution of the chemical composition from the oxide–metal interface to the oxide surface has also been studied. XAS spectra show that Cu diffusion is favoured in the oxide layer for the non-implanted sample, which does not occur for implanted samples. Both Si and Ce ion implantation promotes active diffusion of Cr and Mn from the parent steel to form a protective oxide layer, whereas Mo implantation induces major participation of Fe in the oxide scale. This may have been caused because of volatilisation of molybdenum oxides. [Copyright &y& Elsevier]

Effects of oxygen ion irradiation followed by thermal annealing of single phase (00l) oriented Bi2Sr2Ca1Cu2Ox (Bi-2212) films on SrTiO3(001) synthesized by pulsed laser deposition were studied. Differently from as-deposited films, ion irradiated and thermally annealed ones show a leaf-like grain morphology and a significantly improved electric resistivity behavior. The results suggest that the process, that is, amorphization by ion irradiation followed by recrystallization by thermal annealing, may be a new method to enhance superconducting properties of Bi-2212 films. [Copyright &y& Elsevier]

Luminescent thin films of heteropolytungstate complexes containing lanthanide (europium or samarium) were successfully fabricated by the Langmuir–Blodgett (LB) technique. The pressure–area isotherm of the monolayer of dimethyldioctadecylammonium bromide (DODA) is modified rather markedly when the subphase contains the complex of Na9EuW10O36 or Na9SmW10O36. The above results indicate that the monolayer of DODA has a strong interaction with the polyanions of EuW10O369− (or SmW10O369−). X-ray photoelectron spectra and fluorescent spectra verify that europium and tungsten atoms are incorporated into the LB films. Ultraviolet (UV), fluorescent spectra and low-angle X-ray diffraction experiments demonstrate that these LB films have a well-defined lamellar structure. The LB film containing EuW10O369− can give off strong fluorescence on UV irradiation. The characteristic emission behaviors of europium ions in LB films and in the powder of Na9EuW10O36 are discussed. It is found that the intensity ratio of the 5D0→7F2 transition to the 5D0→7F1 transition in LB film is quite different from that in the powder of Na9EuW10O36. The difference of the ratio indicates that the site symmetry of europium is distorted in LB film, which is probably due to the strong electrostatic interactions between DODA and polyanions. [Copyright &y& Elsevier]

The sol–gel technique has been used to produce titania thin films doped with amino groups on the surfaces. Both propylamine and aminopropyl-triethoxysilane were tested as sources of amino groups and the influence of varying molar concentrations was analysed. The high sol–gel activity of tetraisopropyl-orthotitanate precursors was the driving force for the fixation of amino groups. Fourier transform infrared spectroscopy and X-ray diffraction techniques were used for the physico-chemical characterisation of the thin doped films. The thermal evolution of the amino bonds as well as the formation of a Ti–Si poly-oxide network was analysed at different temperatures. These results open the possibility of producing coatings with a high surface density of amino groups, which are increasingly used in bio-engineering processes. [Copyright &y& Elsevier]

A carbazole-containing amphiphilic Schiff base has been synthesized and was found to form a stable monolayer at the air/water interface. The monolayer can be fabricated into regular Langmuir–Blodgett (LB) film. The LB film shows acidichromism, i.e. when the LB film was exposed to HCl gas a color change was observed and consecutive exposing to NH3 gas the color was recovered. It has been confirmed by the UV-Vis spectra, fluorescence spectra and Fourier transform infrared spectra that such color change was due to the protonation of the imine group in the compound. In a mixed LB film of the compound with a copolymer (polyvinylidene chloride-co-polymethyl methacrylate), similar color change was observed upon photoirradiation. It was found that the acidichromism of the film was alternatively controlled by photoirradiation. [Copyright &y& Elsevier]