Anodic oxide film growth on thin magnetron sputter-deposited titanium layer

A ~ 100 nm thick sputter-deposited titanium layer on electropolished aluminium is used for the investigation of anodic film growth in 1 M H₃PO₄. It is found that the thin titanium layer could not provide sufficient current efficiency for titanium anodic film growth when anodized to the voltage over 80 V due to the occurrence of oxygen evolution. The ruptures of titanium anodic film and the sputtering layer are induced by the development of oxygen bubbles. The penetrated phosphoric acid electrolyte in the ruptured regions of sputtering titanium layer contacts with the aluminium substrate, which is leading to the anodic oxide growth of aluminium. The thickness of the titanium anodic film increases from 10 to 100 V, however, it is reduced from 100 to 150 V due to the thinning of titanium layer. Over 80 V, the sputtering layer at some regions where it is completely ruptured, the anodic film growth of titanium could not be created. A thicker aluminium anodic film is formed on such regions due to the direct connection with the electrolyte.     

Preparation of ZnO:Al thin film on transparent TPT substrate at room temperature by RF magnetron sputtering technique

Aluminum doped ZnO thin films (ZnO:Al) deposited on flexible substrates are suitable to be used as transparent conductive oxide (TCO) thin films in solar cells because of the excellent optical and electrical properties. TPT films are a kind of composite materials and are usually used as encapsulation material of solar panels. In this paper, ZnO:Al film was firstly deposited on transparent TPT substrate by RF magnetron sputtering. The structural, optical, and electrical properties of the film were investigated by X-ray diffractometry (XRD), scanning electron microscope (SEM), UV–visible spectrophotometer, as well as Hall Effect Measurement System. Results revealed that the obtained film had a hexagonal structure and a highly preferred orientation with the c-axis perpendicular to the substrate. Also, the film showed a high optical transmittance over 80% in the visible region and a resistivity of about 3.03 × 10^? 1 Ω·cm.     

Laser-induced surface acoustic waves: An alternative method to nanoindentation for the mechanical characterization of porous nanostructured thin film electrode media

The mechanical characterization of electrode materials in thin film lithium ion batteries is currently a sparse area. However, mechanical studies could offer valuable insight since the performance and breakdown of active materials is electromechanically coupled. In this paper, a porous nanostructured V₂O₅ cathode thin film with demonstrated high electrochemical performance was investigated by a laser-induced surface acoustic wave technique (LiSAW) that mitigates some of the challenges associated with the popular nanoindentation technique. The intent was to explore the capability of LiSAW in measuring the elastic modulus of the nanostructured film such that a reliable methodology could be produced to mechanically characterize challenging electrode materials. LiSAW measured a modulus of 53 ± 4 GPa for the porous V₂O₅ film and had no problems coping with the 40 nm roughness and delicate structure. On the other hand, nanoindentation produced a modulus of 50 ± 10 GPa, which is comparable to LiSAW, but with considerably higher uncertainty from roughness. For porous nanostructured electrodes, and other challenging films, that are too soft, thin, or delicate for traditional nanoindentation measurements, LiSAW is a potentially excellent alternative. LiSAW testing on many other electrode materials would be instrumental in developing a better understanding between the mechanical and electrochemical properties of thin film battery materials.     

Spectroscopic ellipsometry study of thin film thermo-optical properties

Spectroscopic ellipsometry (SE) was employed to realize in-situ monitoring and the determination of thermo-optic coefficients (TOC) of thin films by integrating a temperature controlled hot stage to the ellipsometer and applying the empirical relationship of Cauchy between the refractive index and wavelength in the data analysis. Magnetron sputtered titanium oxide thin films of 350 nm thick both as-deposited and post-deposition annealed were prepared on silicon wafers for this investigation. Results of ellipsometric analysis show that as-deposited TiO₂ films have a negative TOC of ? 1.21 × 10^? 4 K^? 1 at 630 nm over the test temperature range 304–378 K. The post-deposition annealing at 923 K for 2 hours leads an increase in film refractive index to 2.29 from 2.17 for as-deposited TiO₂ films, and an enhancement in TOC up to ? 2.14 × 10^? 4 K^? 1. X-ray diffraction (XRD) and scanning electron microscopy (SEM) cross-sectional analysis were performed for film structure characterization.     

Preparation and characterization of tin diselenide thin film by spray pyrolysis technique

Tin diselenide (SnSe₂) thin film is deposited on to non-conducting glass substrate by spray pyrolysis technique at an optimized substrate temperature of 523 K. Hot probe method is used to identify the type of conductivity of the film to be an n-type semiconductor. X-ray diffraction study reveals the polycrystalline nature of the film with a preferential orientation growth. Spherical shaped grains with an average diameter of 233 nm are observed from the SEM photograph. The elemental composition on the surface of the film is analyzed with EDAX spectrum and formed almost in stoichiometric in composition. Room temperature resistivity of 1.27 × 10⁴ Ω cm is determined using the linear four-probe method. Activation energy of 0.058 eV is determined by studying the variation of resistivity of the film with temperature. Optical absorption spectrum of this sprayed SnSe₂ thin film is analyzed and found to have a direct allowed transition with a band gap of 1.48 eV.     

Synthesis of TiO2 thin films using single molecular precursors by MOCVD method for dye-sensitized solar cells application and study on film growth mechanism

For dye-sensitized solar cells application, in this study, we have synthesized TiO₂ thin films at deposition temperature in the range of 300–750 °C by metalorganic chemical vapor deposition (MOCVD) method. Titanium(IV) isopropoxide, {TIP, Ti(OⁱPr)₄} and Bis(dimethylamido)titanium diisopropoxide, {BTDIP, (Me₂N)₂Ti(OⁱPr)₂} were used as single source precursors that contain Ti and O atoms in the same molecule, respectively. Crack-free, highly oriented TiO₂ polycrystalline thin films with anatase phase were deposited on Si(1 0 0) with TIP at temperature as low as 450 °C. XRD and TED data showed that below 500 °C, the TiO₂ thin films were dominantly grown in the [2 1 1] direction on Si(1 0 0), whereas with increasing the deposition temperature to 700 °C, the main film growth direction was changed to [2 0 0]. Above 700 °C, however, rutile phase TiO₂ thin films have only been obtained. In the case of BTDIP, on the other hand, only amorphous film was grown on Si(1 0 0) below 450 °C while a highly oriented anatase TiO₂ film in the [2 0 0] direction was obtained at 500 °C. With further increasing deposition temperatures over 600 °C, the main film growth direction shows a sequential change from rutile [1 0 1] to rutile [4 0 0], indicating a possibility of getting single crystalline TiO₂ film with rutile phase. This means that the precursor together with deposition temperature can be one of important parameters to influence film growth direction, crystallinity as well as crystal structure. To investigate the CVD mechanism of both precursors in detail, temperature dependence of growth rate was also carried out, and we then obtained different activation energy of deposition to be 77.9 and 55.4 kJ/mol for TIP and BTDIP, respectively. Also, we are tested some TiO₂ film synthesized with BTDIP precursor to apply dye-sensitized solar cell.     

New natively textured surface Al-doped ZnO-TCOs for thin film solar cells via magnetron sputtering

Natively textured surface aluminum doped zinc oxide (ZnO:Al) thin films were directly deposited via pulsed direct current (DC) reactive magnetron sputtering on glass substrates. During the reactive sputtering process, the oxygen gas flow rate was varied from 8.5 sccm to 11.0 sccm. The influences of oxygen flow rate on the structural, electrical and optical properties of naturally textured ZnO:Al TCO thin films with milky surface were investigated in detail. Gradual oxygen growth (GOG) technique was developed in the reactive sputtering process for textured ZnO:Al thin films. The light-scattering ability and optical transmittance of the natively textured ZnO:Al TCO thin films can be improved through gradual oxygen growth method while maintaining a low sheet resistance. Typical natively textured ZnO:Al TCO thin film with crater-like surface exhibits low sheet resistance (R_s ～ 4 Ω), high transmittance (T_a > 85%) in visible optical region and high haze value (12.1%).     

Cobalt sulphide thin films: Chemical bath deposition,growth and properties

In the present report synthesis of CoS thin films was carried out by a modified liquid phase chemical growth process. Dark green coloured CoS thin films with hexagonal wurtzite polycrystalline structure and average grain size of ≈ 15 nm were deposited. Surface morphology reveals a randomly oriented network of elongated thread like grains. The absorption coefficient of the CoS thin film is high (α ≈ 10⁴–10⁵ cm^? 1) and a direct band gap of 1.13 eV has been observed. n-type conduction is found in the deposited films which can be attributed to the lack of stoichiometry.     

Effect of annealing on conversion efficiency of nanostructured CdS/CuInSe2 heterojunction thin film solar cell prepared by chemical ion exchange route at room temperature

We report, the effect of air annealing on solar conversion efficiency of chemically grown nanostructured heterojunction thin films of CdS/CuInSe₂, such 100, 200 and 300 °C air annealed thin films characterized for physicochemical and optoelectronic properties. XRD pattern obtained from annealed thin films confirms tetragonal crystal geometry of CuInSe₂ and an increase in average crystallite size from 16 to 32 nm. An EDAX spectrum confirms expected and observed elemental composition in thin films. AFM represents high energy induced grain growth and agglomeration due to polygonization process. Increase in optical absorbance strength and decrease in energy band gap from 1.36 to 1.25 eV is observed. Increase in charge carrier concentration from 2 × 10¹⁶ to 8 × 10¹⁷ cm^?3 is observed as calculated from Hall effect measurements and an enhancement in solar conversion efficiency from 0.26 to 0.47% is observed upon annealing.     

Issue and challenges facing rechargeable thin film lithium batteries

New materials hold the key to fundamental advances in energy conversion and storage, both of which are vital in order to meet the challenge of global warming and the finite nature of fossil fuels. Nanomaterials in particular offer unique properties or combinations of properties as electrodes and electrolytes in a range of energy devices. Technological improvements in rechargeable solid-state batteries are being driven by an ever-increasing demand for portable electronic devices. Lithium batteries are the systems of choice, offering high energy density, flexible, lightweight design and longer lifespan than comparable battery technologies. We present a brief historical review of the development of lithium-based thin film rechargeable batteries highlight ongoing research strategies and discuss the challenges that remain regarding the discovery of nanomaterials as electrolytes and electrodes for lithium batteries also this article describes the possible evolution of lithium technology and evaluates the expected improvements, arising from new materials to cell technology. New active materials under investigation and electrode process improvements may allow an ultimate final energy density of more than 500 Wh/L and 200 Wh/kg, in the next 5–6 years, while maintaining sufficient power densities. A new rechargeable battery technology cannot be foreseen today that surpasses this. This report will provide key performance results for thin film batteries and highlight recent advances in their development.     

Optical characterization of vacuum evaporated CdZnTe thin films deposited by a multilayer method

CdZnTe thin films of thickness 450–1400 nm have been evaporated under vacuum onto unheated glass substrates, using a multilayer method. During film deposition, the two evaporation sources, separated by two glass cylinders, were maintained at temperatures of 720 K for Zn and at 925–1200 K for CdTe, respectively. After deposition, the samples were annealed in air up to 775 K. The structural and optical properties of both as-deposited and heat-treated samples were investigated. Depending on the preparation conditions and the annealing temperature, the value of the optical band gap, E_g, of respective films varied between 1.16 and 1.63 eV. The obtained results are discussed in correlation with the structure of the films and the role of Zn atoms in CdTe films.     

Transparent with wide band gap InZnO nano thin film: Preparation and characterizations

Novel indium zinc oxide (InZnO) thin film of 100 nm thickness was prepared onto pre-cleaned glass plate by thermal evaporation technique from InZnO nanoparticles. The metal oxide (In–O and Zn–O) bond and In, Zn and O elements present in the films were confirmed by Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy. The X-ray diffraction patterns revealed the mixed phase of cubic In₂O₃ and wurzite-hexagonal ZnO structure. SEM images showed smooth surface with uniform distribution of grains (201–240 nm) over the entire film surface. High transparency and low absorption obtained from optical study. The band gap energy was evaluated to be about 3.46–3.55 eV by Tauc’s plot. The structure, smooth surface and high transparency with wide band gap energy lead the thermally evaporated InZnO nano thin film to be used for transparent layer in optoelectronic devices in the future.     

Thermally driven sign switch of static dielectric constant of VO2 thin film

Smart multifunctional materials exhibiting phase transition and tunable optical and/electrical properties provide a new direction towards engineering switchable devices. Specifically, the reversible, tunable and sign switch dielectric constants via external temperature stimuli observed in vanadium dioxide (VO₂) make it a candidate of choice for tunable and switchable technologies devices. Here we report new aspect of the metal-insulator transition (MIT) through the sign switch of the static dielectric constant ε_S of pure VO₂. As it is shown, the static dielectric constant showed an abrupt change from positive at T < 70 °C to negative at T > 70 °C. ε_S > 0 confirms the insulating phase where charges are localized while ε_S < 0 confirms the metallic phase of VO₂ where charges are delocalized. We report for the first time the tunability of the dielectric constant from a negative sign for the static dielectric constant of VO₂ thin film rarely found in real physical systems. We also demonstrate the tunability and switchability of the real and imaginary part of the dielectric constant (ε) via external temperature stimuli. More specifically, the real (ε) and Imaginary (ε) showed an abrupt thermal hysteresis which clearly confirms the phase transition.     

A new approach towards the growth of cadmium sulphide thin film by CBD method and its characterization

Cadmium sulphide thin films were deposited by the chemical bath deposition method using tartaric acid as a complexing agent and annealed at different temperature in nitrogen atmosphere and characterized. The crystallographic structure and the crystallite size were studied by the X-ray diffraction (XRD) pattern. Transmittance of the deposited film is significantly higher in the visible region. The optical band-gap of deposited film is 2.4 eV and it decreases with increase in annealing temperature. Temperature dependence of resistivity confirmed the semiconducting behaviour of the film. Scanning electron micrographs (SEM) showed the presence of grain particles of size < 1 μm. X-ray photoelectron spectroscopy (XPS) studies supported the composition of cadmium sulphide thin film determined by EMPA and also indicated the presence of carbon and oxygen as impurity in the film.     

Ultrafast excitation relaxation in titanylphthalocyanine thin film

Ultrafast excitation relaxation in the whole Q band of titanylphthalocyanine amorphous thin film fabricated by physical jet deposition was investigated by femtosecond time-resolved pump–probe technique. The measured relaxation dynamics was found to be strongly dependent on the wavelength of the laser beam and consists of three quite different processes: an ultrafast process with a lifetime of 0.5–5 ps, a fast and a long-lived processes with lifetimes of about 5–10 ps and longer than 100 ps, respectively. The initial ultrafast decay appearing to be excitation intensity dependent is suggested to represent a bimolecular exciton–exciton annihilation process with a t^−1/2 time dependence of the excited-state population, assigned to a one-dimensional exciton diffusion. The exciton–exciton annihilation is observed in the pump intensity as low as 0.27 GW/cm².     

Comparison of optical properties of Si and ZnO/CdTe core/shell nanowire arrays

The systematic computations of the short-circuit current density have been performed for Si and ZnO/CdTe core shell nanowire arrays of 1 μm height in order to optimize the structural morphology in terms of nanowire diameter and period. It is found that the best structural configuration for Si leading to the ideal short-circuit current density of 19.6 mA/cm² is achieved for a nanowire diameter and period of 315 nm and 350 nm, respectively. In case of ZnO/CdTe, the ideal short circuit current density is of 24.0 mA/cm², the nanowire diameter and period is of 210 nm and 350 nm, respectively. It is shown that the optimal configuration is more compact in the case of Si nanowire arrays than in the case of ZnO/CdTe nanowire arrays. Since Si has a smaller absorption coefficient than CdTe, a larger amount of material is needed and thus more compact nanowire arrays are required. It is also revealed that core–shell nanowire arrays made of ZnO/CdTe more efficiently absorb light than that of Si, making this device a good candidate for the next generation of nanostructured solar cells.     

New possibility on InZnO nano thin film for green emissive optoelectronic devices

Indium zinc oxide (InZnO) nano thin film was prepared from InZnO nanoparticles (NPs) by thermal evaporation technique. Fourier transform infrared spectroscopy showed the presence of metal-oxide bond. X-ray diffraction pattern revealed the mixed phase structure. The presence of elements In, Zn and O were identified from energy dispersive X-ray analysis. Size of the NPs was found to be 171 and 263 nm by transmission electron microscopy. Scanning electron microscopy image showed the spherical shape uniform morphology with uniform distribution grains. Photoluminescence spectrum exhibited a broad green emission for InZnO nano thin film. The acquired results of structure, smooth morphology and photoluminescence property suggested that the InZnO nano thin film to be a promising material for room temperature green emissive optoelectronic, laser diodes, solar cells and other optical devices.     

Preparation and properties of antiperovskite Mn3NiN thin film

The magnetic and electronic transport properties of the antiperovskite Mn₃NiN thin film deposited on quartz substrate using magnetron sputtering were investigated. The film shows a (100) preferred orientation. It is worthwhile noting that a positive magnetoresistance (MR) effect was found in the whole measured temperature region and the maximum MR value by 31% was obtained at about 300 K under 2 T. On the other hand, when cooling from room temperature, a spin-glass behavior was also observed in the Mn₃NiN film and the Tb shifted to lower temperature with increasing external magnetic field. In contrast to the bulk counterpart, the temperature dependent resistivity of the film shows a semiconductor-like behavior.     

Combined theoretical studies of the optical characteristics of II-IV-V2 semiconductor thin films

The optical absorbance of four ternary thin films, i.e. MgSiP₂, MgGeP₂, MgSiAs₂, MgGeAs₂ have been theoretically examined over a wide range of wavelength from 300 nm to 800 nm. The combination of first-principle electronic structure calculations and the optical matrix approach for modeling the multilayer assembly have been employed for theoretical studies. The analysis of the calculated absorbance spectra at room temperature with unpolarized light and normal incidence, revealed that MgGeAs₂ with a direct energy band gap of 1.6 eV exhibit a considerable high optical absorption, where a thickness of 3.2 μm of this thin film is sufficient to absorb 90% of the incident light and generates a maximum photocurrent of ∼23 mA/cm².     

Effects of substrate parameters on structure and optical properties of ZnO thin films fabricated by pulsed laser deposition

Highly oriented zinc oxide thin films have been grown on quartz, Si (1 1 1) and sapphire substrates by pulsed laser deposition (PLD). The effect of temperature and substrate parameter on structural and optical properties of ZnO thin films has been characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), optical transmission spectra and PL spectra. The experimental results show that the best crystalline thin films grown on different substrate with hexagonal wurtzite structure were achieved at growth temperature 400–500 °C. The growth temperature of ZnO thin film deposited on Si (1 1 1) substrate is lower than that of sapphire and quartz. The band gaps are increasing from 3.2 to 3.31 eV for ZnO thin film fabricated on quartz substrate at growth temperature from 100 to 600 °C. The crystalline quality and UV emission of ZnO thin film grown on sapphire substrate are significantly higher than those of other ZnO thin films grown on different substrates.