The effect of oxygen partial pressure on physical properties of nano‐crystalline silver oxide thin films deposited by RF magnetron sputtering

Nano‐crystalline silver oxide films were deposited on glass and silicon substrates held at room temperature by RF magnetron sputtering of silver target under different oxygen partial pressures. The influence of oxygen partial pressure on the structural, morphological, electrical and optical properties of deposited films was investigated. Varying oxygen partial pressure during the sputter deposition leads to changes of mixed phase of Ag₂O and Ag to a single phase of Ag₂O and to AgO. The X‐ray diffraction and X‐ray photoelectron spectroscopy results showed the formation of single phase Ag₂O with cubic structure at oxygen partial pressures of 2x10^‐2 Pa while the films deposited at higher oxygen partial pressure of 9x10^‐2 Pa showed the formation of single phase of AgO with monoclinic structure. Raman spectroscopic studies on the single phase Ag₂O showed the stretching vibration of Ag‐O bonds. Single‐phase Ag₂O films obtained at oxygen partial pressure of 2x10^‐2 Pa were nano‐crystalline with crystallite size of 20 nm and possessed an electrical resistivity of 5.2x10^‐3 Ωcm and optical band gap of 2.05 eV. The films deposited at higher oxygen partial pressure of 9x10^‐2 Pa were of AgO with electrical resistivity of 1.8x10^‐2 Ωcm and optical band gap of 2.13 eV. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of PbO and Ta2O5 on Some Physical Properties of MgCuZn Ferrites

Two series of MgCuZn ferrites are prepared by addition of Ta⁵⁺ and Pb²⁺ ions, separately. The variations of the sintered density, initial permeability, saturation magnetization, Curie temperature and electrical resistivity with the dopant concentration have been studied. The sintered density was found to increase when PbO content is 0.6 wt% or larger. Samples doped with PbO exhibit an appreciable higher resistivity compared to Ta‐doped and undoped samples as a result of the insulating layers on the grain boundaries. The temperature dependence of the electrical resistivity shows a change in slope in the neighbourhood of Curie temperature for all samples and this has been attributed to the influence of the magnetic ordering on the conduction mechanism. Also PbO addition improves the temperature dependence of the initial permeability. The origin of the beneficial effect of PbO compared to Ta₂O₅ is believed to be attributed to the melting of PbO and formation of liquid phase at grain boundaries.     

Effect of annealing on the properties of chemical bath deposited nanorods of CdSe thin films

Cadmium selenide (CdSe) thin films have been deposited by chemical bath deposition (CBD) on a glass substrate and they are annealed at 450 °C for 1 h. Scanning electron microscopic (SEM) image of as‐deposited CdSe shows the spherical shaped grains distributed over entire glass substrate. When it is annealed at 450 °C, clusters of nano‐rods with star shaped grains are formed. The X‐ray diffraction (XRD) study of the as‐deposited films exhibits a polycrystalline nature and it undergoes a structural phase transition from the metastable cubic to the stable hexagonal phase when annealed at 450 °C. Optical band gap of as‐deposited films (2.0 eV) has a blue shift with respect to the bulk value (1.7 eV) due to quantum confinement. The band gap energies of the films are decreased from 2.0 eV to 1.9 eV due to annealing at the temperature of 450 °C. The electrical resistivity, Hall mobility and carrier concentration of as‐deposited and annealed films are determined.     

Structural Characteristics of Er Doped LiNbO3 Thin Films Grown by the Liquid Phase Epitaxy Method

Erbium (Er³⁺) doped LiNbO₃ single crystal thin films have been grown LiNbO₃ (001) substrate by the liquid phase epitaxy method. The crystallinity was determined by high‐resolution X‐ray diffraction. The lattice mismatch between Er³⁺ doped LiNbO₃ films and LiNbO₃ (001) substrate was investigated by X‐ray rocking curve analysis. Also we studied the structural characteristics of Er³⁺ doped LiNbO₃ films and surface morphology dependent on the film thickness.     

Growth and properties of (Pb0.90La0.10)TiO3 thick films prepared by RF magnetron sputtering with a PbO buffer layer

The (Pb_0.90La_0.10)TiO₃ [PLT] thick films (3.0 μm) with a PbO buffer layer were deposited on the Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrates by RF magnetron sputtering method. The PLT thick films comprise five periodicities, the layer thicknesses of (Pb_0.90La_0.10)TiO₃ and PbO in one periodicity are fixed. The PbO buffer layer improves the phase purity and electrical properties of the PLT thick films. The microstructure and electrical properties of the PLT thick films with a PbO buffer layer were studied. The PLT thick films with a PbO buffer layer possess good electrical properties with the remnant polarization (P_r=2.40 μC cm⁻²), coercive field (E_c=18.2 kV cm⁻¹), dielectric constant (ε_r=139) and dielectric loss (tan δ=0.0206) at 1 kHz, and pyroelectric coefficient (9.20×10⁻⁹ C cm⁻² K⁻¹). The result shows the PLT thick film with a PbO buffer layer is a good candidate for pyroelectric detector.     

Effect of annealing temperature on the structural and optical properties of amorphous Sb2Te2Se thin films

Thin films of Sb₂Te₂Se were prepared by conventional thermal evaporation of the presynthesized material on Corning glass substrates. The chemical composition of the samples was determined by means of energy‐dispersive X‐ray spectrometry. X‐ray diffraction studies on the as‐deposited and annealed films revealed an amorphous‐to‐crystalline phase transition. The as‐deposited and annealed films at T _a = 323 and 373 K are amorphous, while those annealed at T _a= 423 and 473 K are crystalline with a single‐phase of a rhombohedral crystalline structure as that of the source material. The unit‐cell lattice parameters were determined and compared with the reported data. The optical constants (n , k ) of the investigated films were determined from the transmittance and reflectance data at normal incidence in the spectral range 400–2500 nm. The analysis of the absorption spectra revealed non‐direct energy gaps, characterizing the amorphous films, while the crystalline films exhibited direct energy gaps. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Characteristics of GaP Window Layer Grown by Indium‐added Liquid Phase Epitaxy

The effects of added Indium on the growth characteristics of GaP were systematically studied using conventional liquid phase epitaxy technique with Ga‐rich GaP source melt. The GaP growth rate uniformly increase with the source melt of increasing Indium addition against Gallium solvent. These epilayers have mirror‐like surface morphology examined by optical microscope except several grown films with large amount of Indium addition meet a terrible interface. The surface morphologies examined by AFM showed the ripples in samples of R_0.05 and R_0.4 and distinct islands with elliptical base shape in the sample of R_0.7 (R‐In ratio). The epitaxial layer with incorporation of Indium addition during growth had good performance on the carrier concentrations and resistivity. The composition of compound semiconductor become to InGaP at higher amount of In addition to Ga was examined by double‐crystal X‐ray diffraction and the distribution of Indium examined by SIMS also provided the evidences in sample of R_0.7.     

Spray pyrolysis deposition and characterization of highly (100) oriented magnesium oxide thin films

Transparent dielectric thin films of MgO has been deposited on quartz substrates at different temperatures between 400 and 600°C by a pneumatic spray pyrolysis technique using Mg(CH₃COO)₂·4H₂O as a single molecular precursor. The thermal behavior of the precursor magnesium acetate is described in the results of thermogravimetry analysis (TGA) and differential thermal analysis (DTA). The prepared films are reproducible, adherent to the substrate, pinhole free and uniform. Amongst the different spray process parameters, the substrate temperature effect has been optimized for obtaining single crystalline and transparent MgO thin films. The films crystallize in a cubic structure and X‐ray diffraction measurements have shown that the polycrystalline MgO films prepared at 500°C with (100) and (110) orientations are changed to (100) preferred orientation at 600°C. The MgO phase formation was also confirmed with the recorded Fourier Transform Infrared (FTIR) results. The films deposited at 600°C exhibited highest optical transmittivity (>80%) and the direct band gap energy was found to vary from 4.50 to 5.25 eV with a rise in substrate temperature from 500 to 600°C. The measured sheet resistance and the resistivity of the film prepared at 600°C were respectively 10¹³Ω/□ and 2.06x10⁷Ω cm. The surface morphology of the prepared MgO thin films was examined by atomic force microscopy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural and optoelectrical properties of Ga‐doped ZnO semiconductor thin films grown by magnetron sputtering

Transparent conductive gallium‐doped zinc oxide (Ga‐doped ZnO) films were prepared on glass substrate by magnetron sputtering. The influence of substrate temperature on structural, optoelectrical and surface properties of the films were investigated by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), spectrophotometer, four‐point probe and goniometry, respectively. Experimental results show that all the films are found to be oriented along the c‐axis. The grain size and optical transmittance of the films increase with increasing substrate temperature. The average transmittance in the visible wavelength range is above 83% for all the samples. It is observed that the optoelectrical property is correlated with the film structure. The Ga‐doped ZnO film grown at the substrate temperature of 400 °C has the highest figure of merit of 1.25 × 10⁻² Ω⁻¹, the lowest resistivity of 1.56 × 10⁻³ Ω·cm and the highest surface energy of 32.3 mJ/m².     

Microstructural and optoelectrical properties of transparent conducting ZnO:Al thin films for organic solar cells

The Al‐doped zinc oxide (ZnO:Al) thin films were grown on glass substrates by the magnetron sputtering technique. The films were characterized with X‐ray diffractometer, four‐point probe and optical transmission spectroscopy, respectively. The dependence of microstructural, electrical and optical properties on deposition temperature was investigated. The results show that all the films have hexagonal wurtzite structure with highly c‐axis orientation. And the microstrural and optoelectrical properties of the films are observed to be subjected to the deposition temperature. The ZnO:Al film prepared at the deposition temperature of 650 K possesses the best optoelectrical properties, with the lowest electrical resistivity (6.1×10⁻⁴ Ω·cm), the highest average visible transmittance (85.3%) and the maximum figure of merit (0.41 Ω⁻¹). The optical energy gap of the films was estimated from Tauc's law and observed to be an increasing tendency with the increment of the deposition temperature. Furthermore, the refractive index of the films was determined by the optical characterization methods and the dispersion behavior was studied by the single electronic oscillator model.     

Stoichiometric single crystal growth of AgGaS2 by iodine transport method and characterization

High quality single crystals of ternary AgGaS₂ (AGS) semiconductor with chalcopyrite structure have been grown by chemical vapor transport (CVT) technique using iodine as a transporting agent at different growth zone temperatures. The powder X‐ray diffraction and single crystal X‐ray diffraction studies indicate that the as‐grown AGS crystals belong to the tetragonal (chalcopyrite) system with (112) plane as the dominant peak. The full width at half maximum (FWHM) of the X‐ray rocking curve for the as‐grown AGS single crystal is 5 arcsec. The energy dispersive X‐ray analysis (EDAX) and optical transmission spectra of as‐grown AGS single crystals grown at different conditions show the almost same composition and band gap (2.65 eV). Photoluminescence (PL) spectra of as‐grown AGS single crystals show prominent band edge emission at 2.61 eV. The resistivity of the as‐grown AGS single crystal has been measured. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

反应磁控溅射制备AZO薄膜相结构的演化及机理研究

在室温下,利用直流反应磁控溅射技术在不同的氧气流量下沉积ZnO∶ Al (AZO)薄膜.采用XRD、SEM和TEM技术分析薄膜相成分、表面截面形貌及微观结构.结果表明:氧气流量为2.5 sccm时,沉积形成的薄膜为不透明具有金属导电性能的AZO/Zn( AZO)双层复合膜结构;氧气流量为3.5 sccm时,沉积形成了透明导电的AZO薄膜;氧气流量为5.0 sccm时,形成了透明不导电且含有纳米Al2O3颗粒的AZO薄膜;此外,AZO薄膜在400℃退火后,薄膜晶粒长大和(002)晶面方向择优生长更加明显以及高氧气流量沉积的AZO薄膜中的纳米Al2O3颗粒消失.     

BaMoO4 thin films prepared by electrochemical method at room temperature

Highly crystallized BaMoO₄ films were prepared on molybdenum substrates in Ba(OH)₂ solutions by electrochemical method at room temperature. The deposition conditions (reaction temperature and current density) during electrochemical formation were researched. The films were characterized by using the X‐ray Diffraction (XRD), Scanning Electronic Microscopy (SEM) and X‐ray Photoelectron Spectroscopy (XPS) analyses. The XRD analyses show that the films are good crystalline with single scheelite‐type tetragonal structure; the SEM photographs show that the films are densely deposited with double tetragonal tapers in shape; and the XPS analyses reveal that the composition of the BaMoO₄ films (embodied Ba²⁺, Mo⁶⁺ and O^2‐) is in agreement with stoichiometry. The optimum electrochemical conditions for BaMoO₄ films formation are the lower reacting temperature (near room temperature) and the feasible current density (about 1mA/cm²)     

Comparison of tin‐doped indium oxide films fabricated by spray pyrolysis and magnetron sputtering

A comparison of the properties between Tin‐doped Indium Oxide (ITO) films fabricated by sputtering and spray pyrolysis is presented. This analysis shows that the ITO films fabricated by DC magnetron sputtering in pure argon gas requires of a subsequent annealing for the improvement of their structural, electrical and optical properties, when they are compared to films fabricated by single‐stage spray pyrolysis process that includes a new approach. The optimum annealing temperature for ITO films sputtered at room temperature lies in the 300‐350 °C range. Under such conditions, the ITO sputtered films are slightly more resistive than the resistivity (2 × 10^‐4 Ω‐cm) shown by films sprayed at 480 °C using a solution with a 5 % of tin to indium ratio, and almost four times the worst value of the combination of transparency and conductivity determined by the value of the figure of merit (FOM). The sprayed films have a high value of the FOM, 2.9×10^‐2 Ω^‐1, which is comparable with the best published results.     

Properties of Co‐doped ZnO films prepared by electrochemical deposition

We prepared Co‐doped ZnO films by the electrochemical deposition. X‐ray diffraction (XRD), high resolution transmission microscopy (HRTEM), x‐ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), x‐ray absorption near‐edge structure (XANES), vibrating sample magnetometer (VSM), optical absorption, and photoluminescence (PL) measurements were carried out on the samples. The results showed Co atoms substituted Zn atoms in the ZnO lattice without the formation of the impurity phase. VSM measurements showed the ferromagnetic properties for the Co‐doped ZnO samples. When the Co doping concentration increased, the band gaps were widened and the PL peak positions shifted towards the short wavelength direction. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of annealing on the structural,electrical and optical properties of nanostructured TiO2 thin films

Nanostructured titanium dioxide thin films were prepared using reactive pulsed laser ablation technique. Effects of annealing on the structural, morphological, electrical and optical properties are discussed. The structural, electrical and optical properties of TiO₂ films are found to be sensitive to annealing temperature and are described with GIXRD, SEM, AFM, UV‐Visible spectroscopy and electrical studies. X‐ray diffraction studies showed that the as‐deposited films were amorphous and at first changed to anatase and then to rutile phase with increase of annealing temperature. Optical constants of these films were derived from the transmission spectra and the refractive index dispersion of the films, subjected to annealing at different temperatures, is discussed in terms of the single oscillator‐Wemple and Didomenico model. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of the substrate temperature on the structural,optical, and electrical properties of tin selenide thin films deposited by thermal evaporation method

Thin films of tin selenide (SnSe) were deposited on sodalime glass substrates, which were held at different temperatures in the range of 350‐550 K, from the pulverized compound material using thermal evaporation method. The effect of substrate temperature (T_s) on the structural, morphological, optical, and electrical properties of the films were investigated using x‐ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission measurements, and Hall‐effect characterization techniques. The temperature dependence of the resistance of the films was also studied in the temperature range of 80‐330 K. The XRD spectra and the SEM image analyses suggest that the polycrystalline thin films having uniform distribution of grains along the (111) diffraction plane was obtained at all T_s. With the increase of T_s the intensity of the diffraction peaks increased and well‐resolved peaks at 550 K, substrate temperature, were obtained. The analysis of the data of the optical transmission spectra suggests that the films had energy band gap in the range of 1.38‐1.18 eV. Hall‐effect measurements revealed the resistivity of films in the range 112‐20 Ω cm for films deposited at different T_s. The activation energy for films deposited at different T_s was in the range of 0.14 eV‐0.28 eV as derived from the analysis of the data of low‐temperature resistivity measurements. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigation of DTS effect on r.f. magnetron sputtered ZnO thin films

The aim of this study depends on understanding the effect of target‐to‐substrate distance (D_TS) on ZnO thin films deposited by r.f. magnetron sputtering on to glass substrates at room temperature conditions. The D_TS was changed from 35 mm to 65 mm with steps of 5 mm at 165 W and 0.2 Pa. The deposition rate of the films were ranged from 76 Ǻ / min to 146 Ǻ / min, while 10^‐3 Ω.cm was obtained as the resistivity value with the help of four point probe technique. The structural investigations were carried out by using both the x‐ray diffraction (XRD) and high resolution transmission electron microscopy. According to XRD observations, the films were (002) oriented. Surface behaviour of the ZnO films was examined with atomic force microscopy and scanning electron microscopy. The root mean square (RMS) values were varied from 4.6 nm to 22.8 nm. Also, optical properties were obtained from UV–visible spectrophotometer and the transmittances as around 80 %. At 45 mm D_TS value, the minimum resistivity measured as 9 × 10^{− 4} Ω.cm with 76 Ǻ / min deposition rate. The RMS was obtained as 4.9 nm and transmission was measured as 85.30 %, while band gap was 3.45 eV.     

Crystal Data,Photoconductivity and Carrier Scattering Mechanisms in CuIn5S8 Single Crystals

The X‐ray diffraction has revealed that CuIn₅S₈ is a single phase crystal of cubic spinel structure. The value of the unit cell parameter for this crystal is 1.06736 nm. The crystal is assigned to the conventional space group Fd3m. The photocurrent is found to have the characteristic of monomolecular and bimolecular recombination at low and high illumination intensities, respectively. The electrical resistivity and Hall effect of CuIn₅S₈ crystals are measured in the temperature range of 50‐400 K. The crystals are found to be intrinsic and extrinsic above and below 300 K, respectively. An energy band gap of ∼1.35 eV at 0 K, a carrier effective mass of 0.2 m₀ , an acceptor to donor concentration ratio of 0.9, an acoustic phonon deformation potential of 10 eV and a nonpolar optical phonon deformation potential of 15 eV are identified from the resistivity and Hall measurements. The Hall mobility data are analyzed assuming the carrier scattering by polar optical phonons, acoustic combined with nonpolar optical phonons, and ionized impurities.     

Characterization of reactive DC magnetron sputtered TiAlN thin films

Thin films of about 1μm Titanium Aluminum Nitride (TiAlN) were deposited onto mild steel substrates by reactive direct current (DC) magnetron sputtering using a target consisting of equal segments of titanium and aluminum. X‐ray diffraction (XRD) analysis showed that the TiAlN phase had preferred orientations along 111 and 200 with the face‐centered cubic structure. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) analyses indicated that the films were uniform and compact. Photoluminescence (PL) spectra reveal that TiAlN thin films are of good optical quality. Laser Raman studies revealed the presence of characteristic peaks of TiAlN at 312.5, 675, and 1187.5 cm^–1. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)