Characteristics of brush plated ZnTe thin films

Zinc telluride thin films were deposited by the brush plating technique at a potential of −0.90 V (SCE) on conducting glass and titanium substrates at different temperatures in the range 30–90°C. The films were polycrystalline in nature with peaks corresponding to the cubic phase. Direct band gap of 2.30 eV was observed. XPS studiers indicated the formation of ZnTe. Depth profiling studies indicated a uniform distribution of Zn and Te throughout the entire thickness. EDAX measurements were made on the films and it was found that there was a slight excess of Te.     

Study of polycrystalline ZnTe (ZnTe:Cu) thin films for photovoltaic cells

In our work, polycrystalline ZnTe and ZnTe:Cu thin films were deposited by vacuum co-evaporation technology. The conductivity–temperature relationship was measured. And the properties of films were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and differential scanning calorimety (DSC). The results show that the as-deposited films are cubic and that the films annealed at 185°C are cubic and hexagonal. Cu _x Te are observed by XRD and XPS. DSC shows ZnTe:Cu film has a peak of decalescence at 170°C, which means that there can be a change. Therefore we assume ZnTe:Cu thin films have structure changes at 185°C and the existence of Cu _x Te leads to the abnormal conductivity–temperature relationship. During annealing, copper diffuse from grain boundary to lattices. 1/C ²-V curves show that Cu _x Te can form tunneling junction with CdTe, which can improve the back contact.     

Structural,optical, electrical and morphological properties of ZnTe films deposited by electron beam evaporation

ZnTe films were deposited on glass substrates at different substrate temperatures in the range 30–300 °C. The thickness of the films was about 200 nm. The films exhibited cubic structure with preferential orientation in the (111) direction. Band gap values in the range 2.34–2.26 eV are observed with increase of the substrate temperature. The refractive index values are in the range of 2.55–2.92 for the films deposited at different substrate temperatures. It is observed that the conductivity increases continuously with temperature. Laser Raman studies indicated the presence of peaks at 206.9 and 412.2 cm⁻¹corresponding to the first order and second order LO phonon.     

Preparation of nanocomposite for optical application using ZnTe nanoparticles and a zero-birefringence polymer

Surface-modified ZnTe nanoparticles were mixed in a zero-birefringence polymer matrix. Transmission electron microscopy images revealed that aggregates of ZnTe nanoparticles with a diameter of ∼20 nm were uniformly dispersed in the polymer. The transmittance of ZnTe nanocomposites rapidly decreased at wavelengths shorter than the critical wavelength corresponding to the band gap of ZnTe nanoparticles, an effect which became significant as the volume fraction of particles increased. In this way, the optical characteristic of ZnTe nanoparticles was added to the polymer. The intrinsic zero-birefringence was confirmed in the heat-drawn ZnTe nanocomposites. As the ZnTe nanocomposites were left in air, a lowering of transmittance was observed. This was due to the oxidation of Zn and the resultant deposition of Te in the ZnTe nanocomposite, as the light absorption of Te is significant. The formation of oxygen non-permeable SiO₂ films onto the ZnTe nanocomposite by the sol-gel method was useful in preventing oxidation so that the decrement of transmittance decreased from 47.2% to 14.9% at 530 nm near the ZnTe band gap.     

Photoelectrochemical properties of brush plated Cd x Zn1−x Se films

Cd _x Zn_1−x Se films(0 ≤ x ≤ 1) were deposited for the first time by the brushplating technique at room temperature from an aqueous bath containing zincsulphate, cadmium sulphate and selenium oxide. The deposition current densitywas varied in the range of 50–250 mA cm⁻². The as deposited films exhibitedcubic structure. Composition of the films was estimated by EDAX studies. XPSstudies indicated the binding energies corresponding to Zn(2p_3/2), Cd(3d_5/2 and 3d_3/2) and Se(3d_5/2 and 3d_3/2). Optical band gap of the films varied from 1.72 to 2.70 eV as the composition varied from CdSe to ZnSe side. Atomic forcestudies indicated grain size in the range of 20–150 nm. Photoelectrochemical cells were made with polysulphide as the redox electrolyte. The output was maximum for the photoelectrodes of composition Cd_0.9Zn_0.1Se.     

Structural,morphological and optical properties of SnS<Subscript>2</Subscript> thin films by nebulized spray pyrolysis technique

The thin films of Nano crystalline tin disulfide (SnS₂) have been prepared by nebulized spray pyrolysis technique (NSP) with different molar concentrations (0.3, 0.4 and 0.5 M). Cleaned glass substrates were used and the substrate temperature was maintained at 300?°C. The films were deposited using tin tetrachloride monohydrate (SnCl₄·H₂O) and thiourea in de-ionized water and Isopropyl alcohol (1:3 ratio). The prepared films structural, morphological and optical properties were studied using X-ray diffraction (XRD), scanning electron microscope (SEM), UV–Vis spectrophotometer. The structure of the films were found to be face centered cubic with preferential orientation along (002) plane. X-ray line profile analysis was used to evaluate the micro structural parameters such as crystallite size, micro strain, dislocation density and texture coefficient. The average crystallite size values are 60 nm. Morphological results of the SnS₂ thin films are small needle shaped particles and the average grain size was 400 nm. The optical studies revealed that the band gap between 2.65 and 2.72 eV and high optical transmittance 98%. EDAX spectrum of tin disulfide result showed some amount of excess tin was present in the sample. This is the method with very low cost of producing tin disulfide (SnS₂) thin films, which is very important for many applications in industry.     

Effect of Mn doping on the structural,morphological, optical and magnetic properties of indium tin oxide films

We report on the preparation and characterization of high purity manganese (3–9 wt.%) doped indium tin oxide (ITO, In:Sn = 90:10) films deposited by sol–gel mediated dip coating. X-ray diffraction and selected area electron diffraction showed high phase purity cubic In₂O₃ and indicated a contraction of the lattice with Mn doping. High-resolution transmission electron microscopy depicted a uniform distribution of ∼20 nm sized independent particles and particle induced x-ray emission studies confirmed the actual Mn ion concentration. UV-Vis diffuse reflectance measurements showed band gap energy of 3.75 eV and a high degree of optical transparency (90%) in the 100–500 nm thick ITO films. X-ray photoelectron spectroscopy core level binding energies for In 3d_5/2 (443.6 eV), Sn 3d_5/2 (485.6 eV) and Mn 2p_3/2 (640.2 eV) indicated the In³⁺, Sn⁴⁺ and Mn²⁺ oxidation states. Magnetic hysteresis loops recorded at 300 K yield a coercivity H_c ∼ 80 Oe and saturation magnetization M_s ∼ 0.39 μ_B/Mn²⁺ ion. High-temperature magnetometry showed a Curie temperature T _c > 600 K for the 3.2% Mn doped ITO film.     

Synthesis, elaboration and characterization of the new material CuIn3S5 thin films

CuIn₃S₅ compound was prepared by direct reaction of high-purity elemental copper, indium and sulphur. CuIn₃S₅ thin films were prepared from powder by thermal evaporation under vacuum (10⁻⁶ mbar) onto glass substrates. The glass substrates were heated from 30 to 200 °C. The powder was characterized for their structural and compositional properties by using X-ray diffraction (XRD) and energy dispersive X-ray (EDAX). The XRD studies revealed that the powder exhibiting P-chalcopyrite structure. From the XRD data, we calculated the lattice parameters a and c. Then, the cation–anion bond lengths l _AC and l _BC are deduced. The films were characterized for their structural, compositional, morphological and optical properties by using XRD, EDAX, atomic force microscopy and optical measurement techniques (transmittance and reflectance). XRD analysis revealed that the films deposited at a room temperature (30 °C) are amorphous in nature, whereas those deposited on heated substrates (≥75 °C) were polycrystalline with a preferred orientation along (112) of the chalcopyrite phase. The surface morphological analysis revealed that the films grown at different substrate temperature had an average roughness between 1.1 and 4.8 nm. From the analysis of the transmission and reflection data, the values of direct and indirect band gap of the films were determined. We found that the optical band gap decreases when the substrate temperature increases.     

Pulse plated zinc sulphide films and their characteristics

Zinc sulphide thin films were deposited by the pulse plating technique using AR grade Zinc sulphate and sodium thiosulphate precursors. The pH of the deposition bath was adjusted to 2. The duty cycle was varied in the range of 20–60%. Total deposition time was kept constant as 60 min in all the cases. X-ray diffraction studies indicated the formation of single phase cubic zinc sulphide films. After heat treatment the crystal structure transformed to hexagonal structure. Optical absorption measurements indicated a band gap values in the range of 3.6–4.0 eV as the duty cycle decreased. EDAX studies yielded a composition of the films deposited at 50% duty cycle is Zn = 48%, S = 52%. XPS studies indicated the formation of ZnS. The Zn 2p and S 3p peaks are observed. AFM studies indicated a rms value of surface roughness of 55 nm for the films deposited at a duty cycle of 60%.     

Structure and optical properties of polycrystalline Cd1−xZnxTe thin films prepared by simultaneous evaporation

Cd_1–xZn_xTe films were deposited by simultaneous evaporation of CdTe and ZnTe. These Cd_1–xZn_xTe films were of cubic phase, and strongly (1 1 1) oriented as deposited. Predominant direct optical transitions were observed and the band gap varied with zinc content in a non-linear way. A structure development of CdS/CdTe/ZnTe : Cu solar cells with a Cd_1–xZn_xTe buffer layer was proposed.     

Structural,optical and electrical properties of ZnTe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Se<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> thin films

ZnTe_1−x Se _x films were deposited on glass substrates kept at 200 °C by the electron beam evaporation technique. These films exhibited cubic structure and the lattice parameter increased with increase of Tellurium concentration in the films which confirmed the solid solution formation. The grain size is found to increase with Te content. The dislocation density and lattice strain show a decreasing trend with increasing of Te content. Band gap values of 2.73 eV, 2.63 eV, 2.52 eV and 2.41 eV have been calculated for the films of composition ‘x’ = 0.2, 0.4, 0.6 and 0.8, respectively, which confirmed the formation of solid solution between ZnSe and ZnTe. Refractive index of the films increased from 2.535 to 2.826 as the concentration of Te increased. All the films showed high resistivity values. Laser Raman spectral studies of ZnTe_1−x Se _x revealed LO phonon frequencies whose values are located in between the LO phonon frequencies of ZnSe and ZnTe.     

Nanocrystalline TiO2 thin films for NH3 monitoring: microstructural and physical characterization

Nanocrystalline titanium oxide thin films have been deposited by spin coating technique and then have been analyzed to test their application in NH₃ gas-sensing technology. In particular, spectrophotometric and conductivity measurements have been performed in order to determine the optical and electrical properties of titanium oxide thin films. The structure and the morphology of such material have been investigated by X ray diffraction, Scanning microscopy, high resolution electron microscopy and selected area electron diffraction. The X-ray diffraction measurements confirmed that the films grown by this technique have good crystalline tetragonal mixed anatase and rutile phase structure. The HRTEM image of TiO₂ thin film showed grains of about 50–60 nm in size with aggregation of 10–15 nm crystallites. Selected area electron diffraction pattern shows that the TiO₂ films exhibited tetragonal structure. The surface morphology (SEM) of the TiO₂ film showed that the nanoparticles are fine with an average grain size of about 50–60 nm. The optical band gap of TiO₂ film is 3.26 eV. Gas sensing properties showed that TiO₂ films were sensitive as well as fast in responding to NH₃. A high sensitivity for ammonia indicates that the TiO₂ films are selective for this gas.     

Sol–gel derived Co<Subscript>3</Subscript>O<Subscript>4</Subscript> thin films: effect of annealing on structural,morphological and optoelectronic properties

Nanocrystalline Co₃O₄ thin films were prepared on glass substrates by using sol–gel spin coating technique. The effect of annealing temperature (400–700 °C) on structural, morphological, electrical and optical properties of Co₃O₄ thin films were studied by X-ray diffraction (XRD), Scanning Electron Microscopy, Electrical conductivity and UV–visible Spectroscopy. XRD measurements show that all the films are nanocrystallized in the cubic spinel structure and present a random orientation. The crystallite size increases with increasing annealing temperature (53–69 nm). These modifications influence the optical properties. The morphology of the sol–gel derived Co₃O₄ shows nanocrystalline grains with some overgrown clusters and it varies with annealing temperature. The optical band gap has been determined from the absorption coefficient. We found that the optical band gap energy decreases from 2.58 to 2.07 eV with increasing annealing temperature between 400 and 700 °C. These mean that the optical quality of Co₃O₄ films is improved by annealing. The dc electrical conductivity of Co₃O₄ thin films were increased from 10⁻⁴ to 10⁻² (Ω cm)⁻¹ with increase in annealing temperature. The electron carrier concentration (n) and mobility (μ) of Co₃O₄ films annealed at 400–700 °C were estimated to be of the order of 2.4–4.5 × 10¹⁹ cm⁻³ and 5.2–7.0 × 10⁻⁵ cm² V⁻¹ s⁻¹ respectively. It is observed that Co₃O₄ thin film annealing at 700 °C after deposition provide a smooth and flat texture suited for optoelectronic applications.     

Effects of post-deposition annealing temperature and ambient on RF magnetron sputtered Sm<Subscript>2</Subscript>O<Subscript>3</Subscript> gate on n-type silicon substrate

Samarium oxide (Sm₂O₃) thin films with thicknesses in the range of 15–30 nm are deposited on n-type silicon (100) substrate via radio frequency magnetron sputtering. Effects of post-deposition annealing ambient [argon and forming gas (FG) (90% N₂ + 10% H₂)] and temperatures (500, 600, 700, and 800 °C) on the structural and electrical properties of deposited films are investigated and reported. X-ray diffraction revealed that all of the annealed samples possessed polycrystalline structure with C-type cubic phase. Atomic force microscope results indicated root-mean-square surface roughness of the oxide film being annealed in argon ambient are lower than that of FG annealed samples, but they are comparable at the annealing temperature of 700 °C (Argon—0.378 nm, FG—0.395 nm). High frequency capacitance–voltage measurements are carried out to determine effective oxide charge, dielectric constant and semiconductor-oxide interface trap density of the annealed oxide films. Sm₂O₃ thin films annealed in FG have smaller amount of effective oxide charge and semiconductor-oxide interface trap density than those oxide films annealed in argon. Current–voltage measurements are conducted to obtain barrier heights of the annealed oxide films during Fowler–Nordheim tunneling.     

Heat treatment effect on the structural and optical properties of Ga2Se3-Ga2S3 thin films

The structural properties of the 50 mol% Ga₂Se₃-50 mol% Ga₂S₃ system in thin-film form were studied using an X-ray diffraction technique. As-deposited films had an amorphous nature, whereas films heat treated for 2 h at 400 °C in a vacuum of 10^–2 Pa had a single-phase (cubic) polycrystalline nature with lattice constanta=0.532 nm. The optical properties of Ga₂Se₃-Ga₂S₃ thin films as-deposited and as-heat treated were also studied. It was found that heat treatment strongly affects the optical constants as well as the energy gap, which can be attributed to compositional as well as structural changes.     

2-Methoxycycloocta-1,5-dienyl platinum complexes as precursors for platinum nanoparticles

Thermolysis of [Pt₂(μ-OR)₂(C₈H1₂OMe)₂] (R = Me or Ac) in hexadecylamine (HDA) at 210°C under argon atmosphere gave platinum nanoparticles which were characterized by XRD, EDAX and TEM analysis. Both spherical (∼ 10 nm) and rod-like (∼ 19 nm length with aspect ratio of 2·3) face centred cubic (fcc) platinum metal nanoparticles could be isolated. The thermogravimetric analyses of these complexes revealed that they undergo a single step decomposition leading to the formation of platinum metal powder.     

Optical properties of nanocrystalline SnS2 thin films

Thin films of nanocrystalline SnS₂ on glass substrates were prepared from solution by dip coating and then sulfurized in H₂S (H₂S:Ar = 1:10) atmosphere. The films had an average thickness of 60 nm and were characterized by X-ray diffraction studies, scanning electron microscopy, EDAX, transmission electron microscopy, UV-vis spectroscopy, and Raman spectroscopy. The influence of annealing temperature (150-300 °C) on the crystallinity and particle size was studied. The effect of CTAB as a capping agent has been tested. X-ray diffraction analysis revealed the polycrystalline nature of the films with a preferential orientation along the c-axis. Optical transmission spectra indicated a marked blue shift of the absorption edge due to quantum confinement and optical band gap was found to vary from 3.5 to 3.0 eV with annealing temperature. Raman studies indicated a prominent broad peak at ∼314 cm⁻¹, which confirmed the presence of nanocrystalline SnS₂ phase.     

Properties of GaAs films deposited by pulse periodic technique

GaAs is a III-V compound possessing high mobility and a direct band gap of 1.43 eV , making it a very suitable candidate for photovoltaic applications. Thin GaAs films were prepared at room temperature by plating an aqueous solution containing GaCl₃ and As₂O₃ at a pH of 2. The current density was kept as 50 mA cm⁻² and the duty cycle was varied in the range 10–50%. The films were deposited on titanium and tin oxide coated glass substrates. Films exhibited polycrystalline nature with peaks corresponding to single phase GaAs. Optical absorption measurements indicated a direct band gap of 1.40 eV. The surface roughness of the films varied from 3 nm to 6 nm as the duty cycle increased. Raman spectra indicated both the LO and TO phonons for the films deposited at duty cycles above 25%. Photoelectrochemical studies indicated that the current and voltage output are higher than earlier reports on thin film electrodes.     

Effect of Thickness on the Properties of Ga-doped Nano-ZnO Thin Films Prepared by RF Magnetron Sputtering

Nano transparent conductive oxide (TCO) Ga-doped ZnO (GZO) thin films with thickness from 260 nm to 620 nm were prepared on glass substrates by RF magnetron sputtering from a powder target with 3 at.% Ga₂O₃. The substrate temperature was kept at 300 °C. The effect of thickness on the structural, electrical, and optical properties of GZO thin films was investigated. It shows that the nano-GZO films are dense and flat, and have polycrystalline structure with preferentially in the (002) orientation. With the increase of thickness, the crystallinity and the grain sizes of the films are improved, meanwhile the carrier concentration increases and the lowest resistivity of 3.685×10⁻³ Ω cm occurs in the 620 nm thick GZO film. The average optical transmittance of all the films is over 80% in the visible range. Decreasing the thickness, the optical transmission of the films increase, and the absorption edge shifts to shorter wavelength, which means the optical band gap is broadened.     

Synthesis and characterization of thermally evaporated Cu2SnSe3 ternary semiconductor

Copper Tin Selenide (CuSnSe) powder was mechanically alloyed by high energy planetary ball milling, starting from elemental powders. Synthesis time and velocity have been optimized to produce Cu₂SnSe₃ materials. Thin films were prepared by thermal evaporation on Corning glass substrate at T_s = 300 °C. The structural, compositional, morphological and optical properties of the synthesized semiconductor have been analyzed by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM) and transmission electron microscopy. The analyzed powder exhibited a cubic crystal structure, with the presence of Cu₂Se as a secondary phase. On the other hand, the deposited films showed a cubic Cu₂SnSe₃ ternary phase and extra peaks belonging to some binary compounds. Furthermore, optical measurements showed that the deposited layers have a relatively high absorption coefficient of 10⁵ cm⁻¹ and present a band gap of 0.94 eV.