Mott‐hopping processes in neodymium oxide thin films prepared on Si(100) substrates

Thin Nd oxide films were prepared on Si (P) substrates to form MOS structure. The oxide films were annealed at different conditions and their crystal structures were determined by X‐ray diffraction (XRD). The dc electrical transport properties of the devices with amorphous and crystalline Nd oxide were investigated. The current‐temperature J(T) characteristics suggest that the carrier transport through the insulator follows Mott's variable‐range hopping (VRH) mechanism and its results were compared with the results obtained from X‐ray diffraction. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Poole‐Frenkel electrical conduction in europium oxide films deposited on Si(100)

Thin Eu₂O₃ films were prepared on Si (P) substrates to form MOS devices. The oxide crystal structure was determined by X‐ray diffraction (XRD). The electrical transport properties of the devices with amorphous and crystalline Eu oxide were investigated. The current‐voltage and current‐temperature characteristics suggest a Poole‐Frenkel (PF) type mechanism of carrier transport through the device when the applied field is more than 105 V/cm. A deviation from PF leakage current course was found and attributed to the current carrier trapping. We have also observed that, the dielectric spectra of MOS structure are different when the insulator is an amorphous or crystalline thin film. From which we calculate the relaxation time (τ) of the interface (insulator/semiconductor) dipoles. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

High temperature x‐ray diffraction studies of zirconia thin films prepared by reactive pulsed laser deposition

Zirconium oxide thin films have been deposited on Si (100) substrates at room temperature at an optimized oxygen partial pressure of 3x10^‐2 mbar by reactive pulsed laser deposition. High temperature x‐ray diffraction (HTXRD) studies of the film in the temperature range room temperature‐1473 K revealed that the film contained only monoclinic phase at temperatures ≤ 673 K and both monoclinic and tetragonal phases were present at temperatures ≥ 773 K. The tetragonal phase content was significantly dominating over monoclinic phase with the increase of temperature. The phase evolution was accompanied with the increase in the crystallite size from 20 to 40 nm for the tetragonal phase. The mean thermal expansion coefficients for the tetragonal phase have been found to be 10.58x10^‐6 K^‐1 and 20.92x10^‐6K^‐1 along a and c‐axes, respectively. The mean volume thermal expansion coefficient is 42.34x10^‐6 K^‐1 in the temperature range 773‐1473 K. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation of undoped and indium doped ZnO thin films by pulsed laser deposition method

An original modification of the standard Pulse Laser Deposition (PLD) method for preparing both undoped and indium doped zinc oxide (ZnO:In) thin films at low substrate temperature is proposed. This preparation method does not demand any further post‐deposition annealing treatment of the grown films. The developed method allows to grow thin films at low substrate temperature that prevents them from the considerable loss of their intrinsic electrical and optical properties. The influence of deposition parameters on the electrical and optical parameters of the undoped and the indium doped ZnO thin films is also analysed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical and structural characterisation of zinc oxide thin films prepared by sol‐gel process

Zinc oxide thin films have been prepared on different substrates by the sol‐gel method using 2‐methoxyethanol solution of zinc acetate dihydrate stabilized by monoethanolamine. The photoluminescence spectra of the films show the band‐edge and sub‐band transitions. The intensity of the band edge emission peak increases, while the intensity of the deep level emission peak decreases in the films coated on sapphire substrate. Transmittance spectra show that the films are transparent beyond 400 nm. The structural property of the films has been evaluated using X‐ray diffraction. The X‐ray peak intensity of the film (002) grown on sapphire substrate is higher than the films grown on glass and quartz substrates. The AFM images show improvement in the surface of the annealed films as compared to the as‐grown ZnO films coated on sapphire substrates. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure and morphological stability of (Lu1–xEux)2O3 thin films

(Lu_1–xEu_x)₂O₃ smooth, crack‐free, transparent films were prepared by the Pechini sol–gel method and a spin‐coating technique. Thermogravimetric analysis, differential thermal analysis and FITR spectroscopy were used to study the chemical processes during annealing of the films. Film structure, morphology and optical properties were investigated. X‐ray diffraction (XRD) analysis reveals the cubic phase of (Lu_1–xEu_x)₂O₃ films annealed in the 600–1000 °C temperature range. Smooth and crack‐free films with thicknesses of 250–1000 nm were obtained in the 600–800 °C temperature range. The thickness upper limit (1000 nm) of morphological stability of films (Lu_1–xEu_x)₂O₃ on sapphire substrates has been studied.     

Growth,structure and optical characterization of Al‐doped ZnO nanoparticle thin films

Al‐doped ZnO nanoparticle thin films were prepared on glass substrate at the optimum temperature of (410±10) °C by spray pyrolysis technique using zinc nitrate as a precursor solution and aluminium chloride as a dopant. The dopant concentration (Al/Zn at%) was varied from 0 to 2 at%. Structural analysis of the films shows that all the films are of polycrystalline zinc oxide in nature, possessing hexagonal wurtzite structure. The films exhibit variation in peak intensities corresponding to (100), (002) and (101) reflection planes on Al‐doping. The crystallite size calculated by Scherrer formula has been found to be in the range of 35‐65 nm. The optical absorption study shows that the optical band gap in the Al‐doped films varies in the range of 3.11 – 3.22 eV. The width of localized states in the band gap estimated by the Urbach tail analysis has been found to be minimum in case of the 1 at% Al‐doped zinc oxide thin film. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of manganese sulphide thin films deposited by spray pyrolysis

Manganese sulphide (MnS) thin films have been deposited onto glass substrate by a low cost spray‐pyrolysis technique at 220 °C. The as‐deposited MnS thin films have been characterized using scanning electron microscopy (SEM), energy dispersive X‐ray (EDX) spectroscopy, atomic force microscopy (AFM), X‐ray diffraction, UV visible spectroscopy and photo electrochemical (PEC) measurement. The SEM and AFM images showed that the MnS thin films were well covered onto the substrate surface. The as‐deposited raw thin film was found to be amorphous in nature and perfectly crystalline phase after annealing the sample. Optical band gap of the MnS thin films was found to vary from 3.1 to 3.21 eV and the band gap decreases with the increase in film thickness. Optical constants such as refractive index, extinction coefficient have been evaluated using reflectance and absorbance data. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical characterization of thermally evaporated thin CdO films

Cadmium Oxide films have been prepared by vacuum evaporation method on a glass substrate at room temperature. Detailed structural, optical, and electrical properties of the films are presented at different annealing temperatures. The crystal structure of the samples was studied by X‐ ray diffraction. The spectral absorption coefficient of the CdO film at the fundamental absorption region (450‐650nm) was determined using the spectral data of transmittance. The direct and indirect band gap energies were determined and found to be 2.33 eV and 1.95 eV respectively. The third order optical nonlinearities χ(3) of CdO films has been measured used the z‐can technique. The real and imaginary parts of χ(3) have been measured at 514 nm and found to be 1.7x10^‐3 esu and 3.0x10^‐3 esu, respectively. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical and electrical studies on spray deposited ZnO thin films

ZnO thin films were prepared by spray pyrolytic decomposition of zinc acetate onto a glass substrate. These films were analyzed for the optical and electrical properties. Optical studies show that in these films the electronic transition is of the direct transition type. The optical energy gap for the films of different thicknesses is estimated to be in the range 2.98 – 3.09 eV. Electrical studies indicate that the films exhibit thermally activated electronic conduction and the activation energies are found to be dependent on the film thickness. The complex impedance measurements were carried out over a wide range of frequencies at room temperature (300 K). All the impedance spectra contain only a single arc, but the arc has a non‐zero intersection with the real axis in the high frequency region. Also, the arc has its centre lying below with the real axis which indicates the multirelaxation behavior of the films. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of highly c‐axis textured SrTiO3 thin films directly grown on Si(001) substrates by ion beam sputter deposition

Highly c‐axis textured SrTiO₃ (STO) thin films have been directly grown on Si(001) substrates using ion beam sputter deposition technique without any buffer layer. The substrate temperature was varied, while other parameters were fixed in order to study effect of substrate temperature on morphology and texture evolution of STO films. X‐ray diffraction, pole figure analysis, atomic force microscope, and high‐resolution electron microscopy were used to characterize and confirm quality and texture of the STO films. The experimental results show that optimum substrate temperature to achieve highly c‐axis textured films is at 700 °C. The full width at half maximum (FWHM) of 002_STO was found to be 2° and fraction of (011) orientation was as low as 1%. The surface morphology was Volmer‐Weber growth mode with a small roughness ∼1 nm. The lowest leakage current density (5.8 μA/cm² at 2 V) and the highest dielectric constant (ε_STO ∼ 98) were found for highly c‐axis textured films grown at 700 °C. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spray deposition and characterization of undoped and In‐doped tin disulphide thin films

Undoped and Indium doped tin disulphide (SnS₂) thin films had been deposited onto glass substrates at T_s = 300 °C using spray pyrolysis technique under atmospheric pressure with stannous chloride, indium chloride and thiourea as precursors. The structural, optical and electrical properties of the deposited films were characterized. The XRD pattern revealed that the undoped and doped films had preferred orientation along (002) plane with hexagonal structure. FESEM micrographs had shown that morphologies of the films changed with indium doping. Optical constant such as refractive index (n), extinction coefficient (k), real and imaginary parts of dielectric constants were evaluated from transmittance and reflectance spectra in UV‐Visible spectroscopy. The optical absorption data were used to determine the band gap energy and it was found to be 2.75 eV for undoped and 2.50 eV for indium doped films respectively. The room temperature dark resistivity was found to be 4.545 × 10³ Ω‐cm and 5.406 × 10³ Ω‐cm for undoped and In‐doped films respectively.     

Electrical properties of PbxSn1‐xS thin films prepared by hot wall deposition method

The Pb_xSn_1‐xS (x = 0 – 0.25) thin films were prepared on glass substrates by hot wall vacuum deposition. The films were polycrystalline monophase in nature and had orthorhombic crystal structure. The thickness of the films was about 2‐3 μm. The temperature dependences of the conductivity were measured in the temperature range from 150 to 420 K. The films revealed p‐type of conductivity. The Seebeck coefficient and conductivity values of the films was in the range of α = 6 – 360 μV/K and σ = 4.8×10^‐5 – 1.5×10^‐2 Ω^‐1·cm^‐1, respectively, at room temperature depending on concentration of the lead in the films. The lead atoms created the substitution defects Pb_Sn in the crystal lattice of the Pb_xSn_1‐xS. These defects formed the donor energy levels in the band gap. The activation energy of the films increased in the range ΔE_a = 0.121 – 0.283 eV with increasing of the lead concentration. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effects of annealing on the lattice parameter of polycrystalline CdS thin films

Cubic CdS (β‐CdS) polycrystalline thin films were prepared on glass substrates by chemical synthesis at 80 °C. Samples were subjected to thermal treatments (TT) in the range of temperatures (T) 180 – 500 °C during 30 hours in different ambients. Annealing in air and in H₂ produces in CdS larger lattice parameter enlargements (≤2.5 %) when T of TT increases up to T ≤ 500 °C. Whereas, annealing in Ar + S₂ and vacuum provokes intermediate (≤1.2 %) and smaller (≤0.9 %) maxima values of the lattice parameter increments, respectively. Energy band gap (E_g) as a function of T of TT and as a function of the lattice parameter has been also studied where it was observed that E_g behaves in very different manners depending on the ambient chosen for annealing. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure and electrical conduction of Sb2O3 thin films

Antimony trioxide (Sb₂O₃) thin films have been deposited onto glass substrates using thermal evaporation technique at room temperature. The structural feature and surface morphology were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Sandwich‐type structures were deposited with films thickness d = 0.55 μm using evaporated electrodes of silver. Current‐voltage (J‐U) characteristics have been measured at various fixed temperatures in the range 293‐473 K. In all cases, at low electric field (E <10⁴ V/cm), ohmic behavior is observed. However, at high electric field (E >10⁴ V/cm), non‐ohmic behavior is observed. An analysis of the experimental data indicates that in the range of high‐applied electric field, the dominant conduction mechanism is space charge limited currents (SCLC). Using the relevant SCLC theory, the carrier concentration, total trap concentration and the ratio of free charge to trapped charge have been calculated and correlated with changes in the structures of antimony trioxide thin films. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

(1-x)ZnO-xMgO-TiO_2-SnO_2(x=0.1~0.2)高频介电陶瓷的制备、结构与介电性能

采用氧化物固相烧结法制备了不同摩尔比的(Zn_(1-x)Mg_x)(Ti_(0.8)Sn_(0.2))O_3(x=0.1~0.2)高频介电陶瓷,研究了陶瓷的微观结构和介电性能。结果表明:烧结温度超过1000℃时,陶瓷中均形成了立方尖晶石结构的固溶相(Zn,Mg)2(Ti,Sn)O4。当烧结温度为1100℃时的陶瓷致密程度最高;当烧结温度为1200℃且x=0.15时,在10 MHz测试频率下获得了陶瓷的最佳介电性能,其介电常数ε=28.65,介电损耗tanδ=1.02×10-3,满足高频介电陶瓷的使用要求。     

Effects of CdCl2 treatment on properties of CdTe thin films grown by evaporation at low substrate temperatures

The structural, morphological and optical properties of vacuum‐evaporated CdTe thin films were investigated as a function of substrate temperature and post‐deposition annealing without and with CdCl₂/treatment at 400°C for 30 min. Diffraction patterns are almost the same exhibiting higher preferential orientation corresponding to (111) plane of the cubic phase. The intensity of the (111) peak increased with the CdCl₂/annealing treatment. The microstructure observed for all films following the CdCl₂/annealing treatment are granular, regardless of the as‐deposited microstructure. The grain sizes are increased after the CdCl₂/annealing treatment but now contain voids around the grain boundaries. The optical band gaps, E_g, were found to be 1.50, 1.50 and 1.48 eV for films deposited at 200 K and annealed without and with CdCl₂/treatment at 400°C for 30 min respectively. A progressive sharpening of the absorption edge upon heat treatment particularly for the CdCl₂/treated was observed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Morphology,composition, structure and optical properties of thermally annealed Cu2O thin films prepared by reactive DC sputtering method

Abstract

Thin films copper oxides are perspective materials for many optoelectronic applications, including photovoltaics. The samples were deposited on glass and silicon substrates by magnetron sputtering method using Modular Platform PREVAC. After deposition the samples were thermally treated by annealing in oxygen atmosphere for 60?min at 450?°C. Morphology confirms that all the films have crystalline structure. Optical measurements show that the films have wide band gap within the range 2.20÷2.48?eV before and 2.03÷2.40?eV after annealing. The article presents the discussion about the influence of annealing on Cu₂O thin film parameters.     

Optical properties of thermally evaporated CdS thin films

CdS thin films of varying thicknesses were deposited on cleaned glass substrates at room temperature by thermal evaporation technique in a vacuum of about 2 x 10^‐5 torr. UV‐VIS spectra of the films were studied using the optical transmittance measurements which were taken in the spectral region from 300 nm to 1100 nm. The absorbance and reflectance spectra of the films in the UV‐VIS region were also studied. Optical constants such as optical band gap, extinction coefficient, refractive index, optical conductivity and complex dielectric constant were evaluated from these spectra. All the films were found to exhibit high transmittance (∼ 60 ‐ 93 %), low absorbance and low reflectance in the visible/near infrared region from ∼ 500 nm to 1100 nm. The optical band gap energy was found to be in the range 2.28 – 2.53 eV. All the films annealed at 300°C for 4 hours in vacuum (∼ 10^‐2 torr) showed a decrease in the optical transmittance with its absorption edge shifted towards the longer wavelength, leading to the result that the optical band gap decreases on annealing the films. Also, on annealing crystallinity of the films improves, resulting in decrease in the optical transmittance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)