Characterization of Cd1−x Zn x Se thin films deposited at low temperature by chemical route

Optoelectronic technologically important pseudo-binary Cd_1−x Zn _x Se thin films with a variable composition (0 < x < 1) has been developed by chemical bath deposition method. The objective to study growth kinetics, physical, microscopic, compositional, optical, electrical and structural changes. Cd_1−x Zn _x Se have been deposited on non-conducting glass substrate in tartarate bath containing Cd⁺² and Zn⁺² ions with sodium selenosulphate with an aqueous alkaline medium at 278 K. The quality and the thickness of the films are depends upon deposition temperature, deposition time and pH, etc. X-ray diffraction (XRD), atomic absorption spectroscopy, optical absorption, scanning electron microscopy and thermoelectric technique characterized the films. The XRD study indicates the polycrystalline nature in single cubic phase over whole range of composition. Analysis of absorption spectra gave direct type band gap, the magnitude of which increases non-linearly as zinc content in the film is increased and dc electrical conductivity at room temperature was found to decreases from 10⁻⁷ to 10⁻⁸ (Ω cm)⁻¹. All the films show n-type conductivity. The promising features observed are the formation of continuous solid solutions in a single cubic phase.     

Preparation and structural characterization of Zn1?xMnxSe thin films

Undoped and Mn doped ZnSe nanoparticles thin films of thickness ranging from 20 to 120 nm have been successfully synthesized via inert gas condensation (IGC) technique with constant Argon gas flow rate and deposition temperature 300 K. The energy dispersive X-ray analysis (EDX) for freshly deposited Zn_1−xMn_xSe thin films were carried out and revealed that Mn contents (x) were 0, 0.05, 0.16 and 0.25. The as-prepared deposited thin films of different thickness were examined using transmission electron microscope (TEM) and showed that all films were nanocrystalline with particle size ranging from 4.1 to 6.6 nm. The grazing incident in-plane X-ray diffraction (GIIXD) patterns verified nanocrystalline single phase zinc blende structure for 80 nm film thickness for all examined Zn_1−xMn_xSe compound films. A broadening of main characteristic lines (111), (220) and (311) of cubic phase was observed and was attributed to the lower particle size in nanocrystalline examined Zn_1−xMn_xSe compound films.     

Structural and electrical studies of Cd<Subscript>1−x</Subscript>Zn<Subscript>x</Subscript> Te thin film by vacuum evaporation technique

Cd_1−xZn_xTe (where x = 0.02, 0.04, 0.06, 0.08) thin film have been deposited on glass substrate at room temperature by thermal evaporation technique in a vacuum at 2 × 10⁻⁵ torr. The structural analysis of the films has been investigated using X-ray diffraction technique. The scanning electron microscopy has been employed to know the morphology behaviour of the thin films. The temperature dependence of DC electrical conductivity has been studied. In low temperature range the thermal activation energy corresponding to the grain boundary—limited conduction are found to be in the range of 38–48 μeV, but in the high temperature range the activation energy varies between 86 and 1.01 meV. The built in voltage, the width of the depletion region and the operating conduction mechanism have been determined from dark current voltage (I–V) and capacitor-voltage (C–V) characteristics of Cd_1−xZn_xTe thin films.     

Structural and chemical properties of nanocrystalline La<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>CoO<Subscript>3−δ</Subscript> layers on yttria-stabilized zirconia analyzed by transmission electron microscopy

Nanocrystalline La_1−x Sr _x CoO_3−δ (LSC) thin films with a nominal Sr content x = 0.5 were deposited on 3.5 mol% yttria-stabilized zirconia (YSZ) substrates by a low-temperature sol–gel process followed by a rapid thermal annealing procedure at temperatures up to 900 °C. The structural and chemical stability of the as-prepared nanocrystalline LSC and demixing effects within the thin film or at the LSC/YSZ interface were studied after long-time exposure at temperatures between 700 °C and 1,000 °C. The grain size and surface topography were analyzed by scanning electron microscopy. Transmission electron microscopy combined with selected-area electron diffraction, energy-dispersive X-ray spectrometry, and electron-spectroscopic imaging was applied for the investigation of the microstructure and the analysis of the local chemical composition and element distribution on the nanoscale. Chemical potential calculations, which were performed to assess the decomposition of LSC/YSZ as a function of temperature, show good agreement with the experimental results.     

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.     

Structure and magnetic properties of NixZn1?xFe2O4 thin films prepared through electrodeposition method

Nanocrystalline nickel–zinc ferrites Ni _x Zn_1−x Fe₂O₄ thin films have been studied and synthesized via electrodeposition–anodization process. Electrodeposited (NiZn)Fe₂ alloys were obtained from non-aqueous ethylene glycol sulphate bath. The formed alloys were electrochemically oxidized (anodized) in aqueous (1 M KOH) solution, at room temperature, to the corresponding hydroxides. The parameters controlling the current efficiency of the electrodeposition of (NiZn)Fe₂ alloys such as the bath composition and the current density were studied and optimized. The anodized (NiZn)Fe₂ alloy films were annealed in air at different temperatures ranging from 850 to 1000 °C for different times from 1 to 4 h. The change in the crystal structure, crystallite size, microstructure, and magnetic properties of the produced ferrites were investigated using X-ray diffraction patterns (XRD), scanning electron microscope (SEM) and vibrating sample magnetometer (VSM). The results revealed the formation of Ni–Zn ferrites thin films were formed. The crystallite sizes of the produced films were in the range between 32 and 81 nm. High saturation magnetization of 48.81 emu/g was achieved for Ni_0.5Zn_0.5Fe₂O₄ thin film produced after annealing the alloy at 850 °C for 4 h. The annealing process of the oxidized alloy anodization process was found to be first order reaction. The activation energy of the crystallization of Ni–Zn ferrite was found to be 62 KJ/mol.     

Effect of deposition ambient on structural and optical properties of Mg<Subscript>x</Subscript>Zn<Subscript>1−x</Subscript>O alloy thin films grown by RF sputtering

Mg_xZn_1−xO thin films were deposited on Corning eagle 2,000 glass substrates by a RF magnetron sputtering using a ceramic target. The effect of Ar/O₂ ratios on structural and optical properties was investigated. The XRD results showed that the film demonstrated the best structural properties when the Ar/O₂ ratio equal 7:3. Sputtering ambient seemed to have minor effect on the optical properties of Mg_xZn_1−xO thin films.     

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.     

Effect of Mg content on structure and properties of Mg<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>O:Al UV transparent conducting films

Mg _x Zn_1−x O:Al (0 ≤ x ≤ 0.6) UV transparent conducting films were deposited on quartz glass by radio frequency magnetron sputtering. Effect of Mg content on structure, optical and electrical properties of Mg _x Zn_1−x O:Al films was investigated. There is a single phase of basic wurtzite structure of ZnO in Mg _x Zn_1−x O:Al films at x ≤ 0.4, and of a basic structure of cubic structure of MgO at x ≥ 0.6. The band gap can be varied from 3.27 to 5.90 eV by controlling Mg contents. The resistivity of Mg _x Zn_1−x O:Al films increase with increasing Mg content x due to the decrease of Al-doping efficiency. The electrical conduction of Mg _x Zn_1−x O:Al films can be markedly improved by increasing the Al-doping level appropriately and annealing in argon atmosphere at over 500 °C. The maximum band gap of Mg _x Zn_1−x O:Al films with wurtzite structure was found to be 5.35 eV when Mg content x is 0.4, and the minimum resistivity of 5.4 × 10⁻⁴ Ω cm was obtained when the Al/(Zn + Mg + Al) is 0.03 and the annealing temperature is over 500 °C. The average transmittance of Mg _x Zn_1−x O:Al films was higher than 86% in the wavelength region from 300 (x ≥ 0.4) to 800 nm.     

Effect of Zn doping on structure and ferroelectric properties of PST thin films prepared by sol–gel method

(Pb _y Sr_1−y )Zn _x Ti_1−x O_3−x thin films were prepared on ITO/glass substrate by sol–gel process using dip-coating method. The phase structure, morphology and ferroelectric property of the thin film were studied. All the thin films show the typical perovskite phase structure. Both the crystallinity and c/a ratio of the perovskite phase increases initially and then decreases gradually with doping Zn in the thin film. Ferroelectric properties of the Zn-doped PST thin films, including ferroelectric hysteresis-loop, remnant polarization and coercive force, decrease gradually with increasing Zn. And the effect of Zn on ferroelectric properties is more obvious in PST thin film with high content of Pb than that with low Pb although the high lead thin film exhibits high intrinsic ferroelectric properties.     

A Double Energy Transition of Nanocrystalline CdxZn1-xS Films Deposited by Chemical Bath

Ternary films of Cd_xZn_1-xS were deposited on Corning glass substrates by the chemical bath deposition technique at 80°C. A process for depositing thin films of the ternary Cd_xZn_1-xS is proposed. Different induction times in the methodology for films deposition were included. The chemical bath was composed of zinc chloride, thiourea, and cadmium chloride as source of the main ions, ammonium nitrate as complexing agent, and potassium hydroxide for pH control. Groups of samples with different conditions were deposited to obtain the ternary material. The manufacturing processes as well as the chemical reactions that take place during preparation are discussed. The morphology, the crystalline structure, and the optical properties of the deposited films were obtained. X-ray diffraction results revealed hexagonal structures of the Cd_xZn_1-xS material in all the deposited samples and structures of ZnO in some cases. Energy dispersive spectroscopy results show the presence of Cd, Zn, and S as main components of the material. A double transition on the absorption measurements were obtained on the produced ternary films which is associated with a double bandgap energy.     

Chemical solution deposition of CaCu<Subscript>3</Subscript>Ti<Subscript>4</Subscript>O<Subscript>12</Subscript> thin film

CaCu₃Ti₄O₁₂ (CCTO) thin film was successfully deposited on boron doped silica substrate by chemical solution deposition and rapid thermal processing. The phase and microstructure of the deposited films were studied as a function of sintering temperature, employing X-ray diffractometry and scanning electron microscopy. Dielectric properties of the films were measured at room temperature using impedance spectroscopy. Polycrystalline pure phase CCTO thin films with (220) preferential orientation was obtained at a sintering temperature of 750°C. There was a bimodal size distribution of grains. The dielectric constant and loss factor at 1 kHz obtained for a film sintered at 750°C was k ∼ 2000 and tan δ ∼ 0.05.     

Preparation of highly transparent conductive Al-doped ZnO thin films and annealing effects on properties

Aluminum-doped ZnO (ZAO) thin films were deposited on fused quartz substrates by radio frequency sputtering in pure argon ambient at 450 °C. Effects of in situ annealing temperature and annealing atmosphere on microstructure, electrical and optical properties of ZAO films have been investigated. Results showed that as-grown film without annealing treatments attained lowest resistivity of 1.1 × 10⁻⁴Ω cm. And all films performed high average transmittance greater than 90% in visible region. X-Ray diffraction (XRD), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) were utilized to characterize the microstructure properties of films. XRD results indicated that as-grown film had higher crystalline quality and larger grain size than annealed films. Al atoms replaced Zn efficiently to provide electrons stable in all samples. PL spectra revealed that high annealing temperature and oxygen atmosphere would generate more Zn vacancy (V_Zn) and oxide antisite defect (O_Zn), respectively and composition content results from XPS provided supports to this.     

Structural disorder and solid state transformations in single crystals of Zn x Cd1−x S and Zn x Mn1−x S

Single crystals of Zn _x Cd_1−x S and Zn _x Mn_1−x S were grown from the vapour phase at 1100°C in the rangex=0·9 to 1. X-ray characterization shows that polytypes and disordered structures occur in Zn _x Cd_1−x S forx ≥ 0·94, whereas Zn _x Mn_1−x S displays disordered and polytype structures in the entire rangex=0·9 to 1. It is observed that Zn _x Cd_1−x S and Zn _x Mn_1−x S undergo a 2H-6H solid state transformation on annealing in vacuum around 600°C. Experimental analysis of the intensity distribution along the 10·L reciprocal lattice row as recorded on a single crystal diffractometer from partially transformed crystals shows that the mechanism of the transformation cannot be explained in terms of the one-parameter models of non-random faulting reported earlier. A two-parameter theoretical model with α representing the probability of random insertion of a fault in the 2H structure and β representing the probability of the growth of the 6H nucleus, is developed both for a deformation mechanism and a layer displacement mechanism. It is found that the theoretical model of non-random deformation faulting with β ≫ α approximates the actual mechanism of transformation in these crystals.     

Growth of highly orientated strontium barium niobate thin films on Si substrates through the sol–gel process using a K: SBN template layer

We report the growth of highly C-axis orientation of Sr _x Ba_1−x Nb₂O₆ (SBN) thin films on p-type (100) Si substrates by using a potassium-substituted SBN template layer with the sol–gel method. The crystallization of SBN thin films was found closely related to the potassium ion doping concentration and the postannealing temperature of the K-SBN template layer. Secondary ion mass spectrometry analysis showed that potassium elements were accumulated at the interface of the template layer and silicon substrate. SBN films postannealed at 750 °C with K-SBN template layer has a smaller full width at half maximum of X-ray rocking curve of 2.45° than that of 5.40° for the pure SBN films. By introducing a template layer, the surface morphologies of SBN films fabricated on silicon substrate were greatly improved.     

Solution-sol-gel processing of superconductors

Bulk materials and thin films of pure and homogeneous YBa₂Cu₃O_7−x and Bi₂Sr₂CaCu₂O_8+x compounds were prepared by a nanocomposite solution-sol-gel (SSG) method. The superconducting oxides of YBa₂Cu₃O_7−x and Bi₂Sr₂CaCu₂O_8+x were prepared at very low temperatures i.e. 750°C and 850°C, respectively by SSG method. Pellets sintered from these nanophasic sol powders showed sharp resistivity drops atT _c ∼ 90°K for YBa₂Cu₃O_7−x andT _c∼67°K for Bi₂Sr₂CaCu₂O_8+x . Thin films were prepared using triphasic sol of Y, Ba, Cu and tetraphasic sol of Bi, Sr, Ca and Cu on MgO and SrTiO₃ substrates. The triphasic sol coated on SrTiO₃ substrates and calcined at 800°C for 12h showed the formation of superconducting phase, YBa₂Cu₃O_7−x with preferred orientation along theC-axis. X-ray diffraction patterns of the Bi₂Sr₂CaCu₂O_8+x films on MgO substrate showed the formation of the superconducting phase with preferential orientation along the C-axis and the microwave absorption data as a function of temperature of this film revealed the onset temperature to be 90°K.     

Optical,structural and electrical investigations on PbTe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> alloys

The fabrication of devices with lead salts and their alloys with detecting and lasing capabilities has been an important technological development. The high quality polycrystalline thin films of PbTe_1−x S _x with variable composition (0 ≤ x ≤ 1) have been deposited onto ultra clean glass substrates by vacuum evaporation technique. Optical, structural and electrical properties of PbTe_1−x S _x thin films have been examined. Absorption coefficient and band gap of the films were determined by absorbance measurements in wavelength range 2,500–5,000 nm using FTIR spectrophotometer. Sample nature, crystal structure and lattice parameter of the films were determined from X-ray diffraction patterns. DC conductivity and activation energy of the films were measured in temperature range 300–380 K through I–V measurements.     

Growth and characterization of laser-deposited Ag-doped YBa2Cu3O7−x thin films on bare sapphire

Microstructural and superconducting properties of YBa₂Cu₃O_7−x thin films grownin situ on bare sapphire by pulsed laser deposition using YBa₂Cu₃O_7−x targets doped with 7 and 10 wt% Ag have been studied. Ag-doped films grown at 730°C on sapphire have shown very significant improvement over the undoped YBa₂Cu₃O_7−x films grown under identical condition. A zero resistance temperature of 90 K and a critical current density of 1·2×10⁶ A/cm² at 77 K have been achieved on bare sapphire for the first time. Improved connectivity among grains and reduced reaction rate between the substrate and the film caused due to Ag in the film are suggested to be responsible for this greatly improved transport properties.     

Synthesis and temperature dependent photoluminescence of Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Mg<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O films grown by ultrasonic spray pyrolysis

Zn_1−x Mg _x O films were deposited on single crystal Si (100) substrates using ultrasonic spray pyrolysis under ambient atmosphere. A strong ultraviolet near-band-edge (NBE) emission was observed in the room temperature photoluminescence (PL) measurement for all the as-grown Zn_1−x Mg _x O films, while the deep-level emission was almost undetectable, suggesting that the obtained Zn_1−x Mg _x O-based films are well close to stoichiometry and of optically high quality. A distinct blue-shift of NBE emission peak from 386 nm to 358 nm was observed as the Mg concentration increases from 0% to 25 %. The photoluminescence spectra as a function of temperature were also investigated to examine the emission mechanism of Zn_1−x Mg _x O films.     

Preparation of ferroelectric PZT films by thermal decomposition of organometallic compounds

Transparent PZT thin films with perovskite structure were successfully obtained by thermal decomposition of organometallic compounds at the temperatures of 500 to 700° C. The films deposited on platinum substrates were smooth and uniform, but microcrackings were observed in the films deposited on fused silica substrates. The ratio of metal composition in the PZT film agreed with that in the mixture of starting materials. Films obtained at 700° C on platinum substrate showed a hysteresis loop. A spontaneous polarization was 35.65μC cm⁻², a saturation remanent polarization was 30.56μC cm⁻² and a coercive field was 45 kV cm⁻¹. Dielectric constant and dielectric loss angle were about 300 and 0.05, respectively.