Some structural properties of CdO:F films produced by ultrasonic spray pyrolysis method

The fluorine doped cadmium oxide (CdO:F) samples have been deposited at 250 °C by ultrasonic spray pyrolysis method. Cadmiumacetat-dihydrat and ammonium fluoride have been taken as a source of cadmium and fluorine-dopant respectively. The thickness of the CdO:F samples was about 1.4 μm. X-ray diffraction pattern of the CdO:F samples has revealed that the samples are polycrystalline with cubic sodium chloride structure. There are shifts of the d values (interplanar spacing) for CdO:F samples with respect to standard CdO film. The lattice parameters for cubic structure have been calculated using the Bragg equation. The texture coefficients calculated for various planes at different fluorine concentrations indicate that the samples have exhibited (111) and (200) preferential orientations.     

Annealing effect on structural and electrical properties of thermally evaporated Cd1−xMnxS nanocrystalline films

Thin films of Cd_1−xMn_xS (0 ≤ x ≤ 0.5) were deposited on glass substrates by thermal evaporation. All the films were deposited at 300 K and annealed at 573 K. The as-deposited and the annealed films were characterized for composition, structure and microstructure by using energy-dispersive analysis for X-rays, X-ray diffraction, scanning electron microscopy and atomic force microscopy. Electrical conductivity was studied in the temperature range 190-450 K. All the films exhibited wurtzite structure of the host material with the grain size varying in the range between 36 and 82 nm. Resistivity of all the films is strongly dependent on Mn content and annealing temperature and lies in the range 13-160 Ω cm.     

Structural, electrical and optical properties of Bi2Se3 and Bi2Se(3−x)Tex thin films

Thin films of Bi₂Se₃, Bi₂Se_2.9Te_0.1, Bi₂Se_2.7Te_0.3 and Bi₂Se_2.6Te_0.4 are prepared by compound evaporation. Micro structural, optical and electrical measurements are carried out on these films. X-ray diffraction pattern indicates that the as-prepared films are polycrystalline in nature with exact matching of standard pattern. The composition and morphology are determined using energy dispersive X-ray analysis and scanning electron microscopy (SEM). The optical band gap, which is direct allowed, is 0.67 eV for Bi₂Se₃ thin films and the activation energy is 53 meV. Tellurium doped thin films also show strong optical absorption corresponding to a band gap of 0.70-0.78 eV. Absolute value of electrical conductivity in the case of tellurium doped thin film shows a decreasing trend with respect to parent structure.     

Cr1−xAlxN coatings deposited by lateral rotating cathode arc for high speed machining applications

In this work, a series of Cr_1−xAl_xN (0 ≤ x ≤ 0.7) coatings were deposited on high speed steel substrates by a vacuum arc reactive deposition process from two lateral rotating elemental chromium and aluminum cathodes in a flowing pure nitrogen atmosphere. The composition, structural, mechanical, and tribological properties of the as-deposited coatings were systematically characterized by energy dispersive analysis of X-rays, X-ray diffraction, nanoindentation, and ball-on-disc tribometer experiments. All of the as-deposited CrAlN coatings exhibited a higher hardness than CrN, showing a maximum hardness of about 40 GPa (at around X = 0.63) which is twice higher than that of the CrN. The wear performance under ambient conditions of the CrAlN coatings was found much better, with both lower friction coefficient and wear rate, than TiAlN coatings deposited by the same technique. The wear rate of the CrAlN coatings against alumina counterpart was about 2-3 orders in magnitude lower than that of the TiAlN coatings. Selected CrAlN coatings with the highest hardness were also deposited on some WC-based end-mills. An evident better performance of the CrAlN-coated end-mills was observed than the TiAlN-coated ones for cutting a hardened tool steel material under high speed machining conditions.     

Structure and optical properties of AlxZn1−xO alloys by sol-gel technique

Al_xZn_1−xO (x = 0-0.5) thin films were prepared on quartz glass substrates by sol-gel technique. X-ray diffraction (XRD), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) were employed for microstructure characterization of these thin films. In films with up to 20 at.% Al incorporation, compound nano-crystal phase was observed while wurtzite structure disappeared. Zn3d electron binding energy and Zn LMM‘s chemical shift were both increased by more than 0.4 eV. Transmittance spectra revealed that these films possessed high transmittance in the visible region, and the end of UV absorption edge shifted to less than 300 nm when Al content exceeds 20 at.% due to quantum confinement effect.     

MgxZn1−xO (x = 0-1) films fabricated by sol-gel spin coating

Mg_xZn_1−xO films were deposited onto the glass substrate by a sol-gel spin coating method. The drying and annealing temperatures were 300 and 500 °C in air. As x varies from 0 to 1, it was observed that the crystal structure is changed from wurtzite ZnO to cubic MgO. The morphology characterizations of these films were observed by scanning electron microscope. The randomly oriented hexagonal nanorods were gown on the glass surface when x = 0 and 0.25, which became disappeared with increasing Mg contents. The optical properties of these films were investigated by room-temperature photoluminescence (PL) and UV-vis absorption spectra, which show that the optical band gap and photoluminescence in the visible and UV regions can be ideally tuned by varying the Mg contents in the Mg_xZn_1−xO alloy films.     

Optical properties of nanocrystalline Ga1−xInxSb/SiO2 films

Ga_1−xIn_xSb (x=0.19, 0.38, 0.63) nanoparticles embedded in a SiO₂ matrix were grown on the glass substrates by radio-frequency magnetron co-sputtering. X-ray diffraction patterns strongly support the existence of nanocrystalline Ga_1−xIn_xSb in the SiO₂ matrix. The changes in binding energies with Ga_1−xIn_xSb nanocrystals deposition have been directly observed by X-ray photoemission spectroscopy, and these show the existence of Ga_1−xIn_xSb nanocrystals in the SiO₂ matrix. Room-temperature Raman spectra show that the Raman peaks of the Ga_1−xIn_xSb-SiO₂ composite film have a larger red-shift of about 95.3 cm⁻¹ (longitudinal-optical mode) and 120.1 cm⁻¹ (transverse-optical mode) than that of bulk GaSb, suggesting the existence of phonon confinement and tensile stress effects. Additionally, the room-temperature optical transmission data exhibit a large blue-shift with respect to that of the bulk semiconductor due to the strong quantum confinement effect.     

Microstructure and optical properties of MgxZn1−xO thin films grown by means of pulsed laser deposition

The single-phase epitaxial Mg_xZn_1−xO (0.4 < x < 0.9) alloy films with wide band gap have been deposited on cubic LaAlO₃ (LAO) (100) substrates by pulsed laser deposition (PLD). X-ray diffraction measurement and TEM photograph indicate that the cubic phase could be stabilized up to Zn content about 0.6 without any phase separation. Films and substrates have a good heteroepitaxial relationship of (100) _MgxZn1−xO||(100)_LAO (out-of-plane) and (011)_MgxZn1−xO||(010)_LAO (in-plane)_. The lattice parameters a of Mg_xZn_1−xO films increase almost linearly with increasing ZnO composition, while the band gap energy of the materials increases from 5.17 to 5.27 eV by alloying with more MgO. The cross-section morphology reveals layer thickness of about 250-300 nm and AFM scan over a 30 μm × 30 μm area reveals a surface roughness R_a of about 100 nm.     

Band alignment of Cd(1 − x)ZnxS produced by spray pyrolysis method

Cd_(1 − x)Zn_xS thin films have been grown on glass substrates by the spray pyrolysis method using CdCl₂ (0.05 M), ZnCl₂ (0.05 M) and H₂NCSNH₂ (0.05 M) solutions and a substrate temperature of 260 °C. The energy band gap, which depends on the mole fraction × in the spray solution used for preparing the Cd_(1 − x)Zn_xS thin films, was determined. The energy band gaps of CdS and ZnS were determined from absorbance measurements in the visible range as 2.445 eV and 3.75 eV, respectively, using Tauc theory. On the other hand, the values calculated using Elliott-Toyozawa theory were 2.486 eV and 3.87 eV, respectively. The exciton binding energies of Cd_0.8Zn_0.2S and ZnS determined using Elliott-Toyozawa theory were 38 meV and 40 meV, respectively. X-ray diffraction results showed that the Cd_(1 − x)Zn_xS thin films formed were polycrystalline with hexagonal grain structure. Atomic force microscopy studies showed that the surface roughness of the Cd_(1 − x)Zn_xS thin films was about 50 nm. Grain sizes of the Cd_(1 − x)Zn_xS thin films varied between 100 and 760 nm.     

Sputtering deposited ternary Zn1−xCdxO crystal films on Si(111) substrates

Using the d.c. reactive magnetron sputtering method we have successfully deposited completely (002)-oriented ternary Zn_1−xCd_xO (0≤x≤0.6) alloy crystal films without Cd segregation on Si(111) substrates. X-Ray photoelectron spectroscopy measurements show that Cd/Zn ratios in the films are nearly consistent with those in the targets. The Zn and Cd exist only in oxidized states, no evidence of metallic Zn or Cd was observed. The O/(Cd+Zn) atomic ratios of the films are in the range of 0.89-0.98. Transmission electron microscopy measurements show that for the (002)-oriented films the grains are columnar structures with the c-axis perpendicular to the Si substrate. By post-annealing treatments in O₂ ambient, the crystal quality of the Zn_1−xCd_xO films can be improved. For the sample of x=0.2, the optimal annealing temperature is 500 °C.     

On certain properties of CdxHg1−xTe thin solid films (x⩽0.2)

The Hall coefficient R_H, electrical conductivity σ and Hall mobility μ_H have been measured in thinCd_xHg_1?xTe solid films over a range of thickness from 1.0 to 12 μm for x as high as 0.2. The dependences of the electrical properties on temperature and thickness were measured in the temperature range 77–300 K.The temperature and thickness dependences of the mobility are discussed on the basis of the relation $\text{1}\text{μ}{}_{\mathrm{<mtext>H</mtext>}}\text{=}\text{1}\text{μ}{}_{\mathrm{<mtext>b</mtext>}}\text{+F}$ where the first term is due to scattering in the bulk material and F is a term used to account for the (lack of) crystalline structure and the effects of film thickness.     

Electrical properties of ZnO/Au/ZnS/Au films deposited by ultrasonic spray pyrolysis

Polycrystalline ZnS semiconducting films have been prepared by ultrasonic spray pyrolysis technique in the form of planar and sandwich configurations using amorphous and ZnO coated glass substrates. Deposition of ZnS films by the spray pyrolysis has been studied extensively by several investigators and the process parameters have been optimized to obtain films with good characteristics. However we report for the first time the preparation of ZnS films sandwiched between top and bottom electrodes on the transparent conducting ZnO films that have been produced by the spray pyrolysis technique. The produced ZnS films have been crystallized in a wurtzite structure. The electrical properties of the samples having planar and sandwich structures have been measured in dark at room temperature by applying the voltage values between 0.01 and 100 V.     

Structural, magnetic and dielectric properties of Bi1−ySryFe(1−y)(1−x)Sc(1−y)xTiyO3 (x = 0-0.2, y = 0.1-0.3) ceramics

In this study, bulk ceramics with general formula Bi_1−ySr_yFe_{(1−y)(1−x)}Sc_(1−y)xTi_yO₃ (x = 0-0.2, y = 0.1-0.3 mol%) were prepared by traditional solid-state reaction method. As a comparison, bulk BiFeO₃ (BF) was also sintered by rapid sintering method. Their structural, magnetic, dielectric properties were investigated. X-ray diffraction analysis indicated that apart from a small amount of secondary phase detected in BF, all other samples crystallized in pure perovskite structure and maintained original R3c space group. The room temperature M-H curves were obtained. While BF had a coercive magnetic field (H_c) of 150 Oe, Bi_1−ySr_yFe_1−yTi_yO₃ solid solutions had a much larger value (for y = 0.1, 0.2, 0.3, H_c were 4537, 5230 and 3578 Oe, respectively). Sc³⁺ substitution decreased the H_c values of these solid solutions remarkably, and resulted in soft magnetic properties, as well as a decrease of the dielectric loss. At 1 MHz, the tan δ of Bi_0.7Sr_0.3Fe_0.7(1−x)Sc_0.7xTi_0.3O₃ with x = 0.05, 0.1, 0.15, 0.2 were 0.1545, 0.1078, 0.1046 and 0.1701, respectively.     

Growth and electrical properties of ZnO thin films deposited by novel ion plating method

The URT(Uramoto-gun with Tanaka magnetic field)-IP(ion plating) method is a technique for depositing a thin film on a substrate. This method offers the advantage of low-ion damage, low deposition temperatures, large area deposition and high growth rates. Ga-doped ZnO thin films were grown using the URT-IP method, and the material properties were evaluated. The quality of ZnO thin films grown by the URT-IP method was found to be sensitive to oxygen supply during growth. It was observed that the saturation point of the growth rate corresponding to the optimum oxygen supply leads to the best electrical properties. The profiles of the dependence of film properties on oxygen supply revealed a part of growth mechanism of the URT-IP method.     

Decomposition of (Ti2xFe1−xSb1−x)O4 solid solutions below 1673 K

The pseudo-binary TiO₂-FeSbO₄ system was investigated by means of thermogravimetric analysis below 1673 K in O₂. Rutile-type solid solutions were synthesised at 1373 K in O₂ by means of a solid state reaction between the two pure end members TiO₂ (rutile) and FeSbO₄ mixed in stoichiometric amounts. Thermal stability of the (Ti_2xFe_1−xSb_1−x)O₄ solid solution increases with rutile content; equimolar (Ti_1.00Fe_0.50Sb_0.50)O₄ solid solutions decompose at about 1673 K forming a TiO₂-enriched solid solution and FeSbO₄, that subsequently decomposes into Fe₂O₃ (hematite) and a volatile Sb oxide, probably Sb₄O₆. For compositions characterised by higher Ti content the decomposition temperature is higher than 1673 K.     

Morphologies and crystal structures of nano-sized Ba1−xSrxTiO3 primary particles prepared by flame spray pyrolysis

Nano-sized Ba_1−xSr_xTiO₃ (BST) powder was prepared by flame spray pyrolysis using “CA-assisted” spray solution. The effects of the mole ratios of Ba to Sr components on the mean sizes, morphologies, and crystal structures of the BST powder prepared by flame spray pyrolysis were investigated. The precursor powders obtained by flame spray pyrolysis had large size, fractured and hollow structures irrespective of the mole ratios of Ba to Sr components. The post-treated BST powders had slightly aggregated morphology of the primary particles with nanometer sizes. The slightly aggregated BST powders turned to nano-sized primary particles by a simple milling process. The milled BaTiO₃ particles post-treated at temperature of 1000 °C had spherical-like shape. On the other hand, the milled Ba_0.5Sr_0.5TiO₃ and SrTiO₃ particles had square shape. The mean sizes of the milled BaTiO₃, Ba_0.5Sr_0.5TiO₃ and SrTiO₃ particles were each 110, 32, and 48 nm. Phase pure BST powder was obtained at a post-treatment temperature of 1000 °C irrespective of the mole ratios of Ba to Sr components. The BaTiO₃ powder had tetragonal crystal structure. On the other hand, the BST except for the BaTiO₃ composition had cubic crystal structures at post-treatment temperature of 1000 °C. The mean crystallite sizes of the milled Ba_1−xSr_xTiO₃ primary particles were changed from 29 to 37 nm according to the mole ratios of Ba to Sr components.     

Hydrothermal synthesis of nanocrystalline MxZn1−xFe2O4 (M=Ni, Mn, Co; x=0.40-0.60) powders

A series of nanocrystalline M_xZn_1−xFe₂O₄ (M=Ni, Mn and Co; x=0.40-0.60) powders have been successfully prepared via hydrothermal process and characterized by XRD, TEM and IR techniques. The effects of reaction temperature and the initial pH value of the starting suspension solution on the particulate properties such as the particle size and morphology are discussed. IR spectra indicate that there are no hydroxyl in as-prepared Ni_xZn_1−xFe₂O₄ and Co_xZn_1−xFe₂O₄ powders, while there are obvious hydroxyl adsorption on the IR spectrum of Mn_xZn_1−xFe₂O₄ powder.     

Influence of Fe ions on the photocatalytic activity of TiO2 films prepared by micro-plasma oxidation method

Microporous titanium dioxide thin films have been fabricated on titanium plates by the micro-plasma oxidation method with the electrolyte of H₂SO₄. The influence of Fe³⁺ ions addition in the electrolyte on the photocatalytic activities was investigated. The results reveal that titanium dioxide thin films produced with Fe³⁺ addition electrolyte exhibit higher photoactivity than pure electrolyte for the oxidation of rhodamine B. The removal of rhodamine B reaches 90% for 30 min when Fe³⁺ addition concentrate is 0.2 g/L. Experimental results of X-ray diffraction and atom force microscopy show that the increase in activity is related to change in the lattice parameters and cell volume.     

Structural, optical and magnetic properties of Zn1 − xMnxO micro-rod arrays synthesized by spray pyrolysis method

Undoped and Mn-doped ZnO micro-rod arrays were fabricated by the spray pyrolysis method on glass substrates. X-ray diffraction and scanning electron microscopy showed that these micro-rod arrays had a polycrystalline wurtzite structure and high c-axis preferred orientation. Photoluminescence studies at 10 K show that the increase of manganese content leads to a relative decrease in deep level band intensity with respect to undoped ZnO. Magnetic measurements indicated that undoped ZnO was diamagnetic in nature whereas Mn-doped ZnO samples exhibited ferromagnetic behavior at room temperature, which is possibly related to the substitution of Mn ions (Mn^2 +) for Zn ions in the ZnO lattice.     

Structural and electrical properties of La2−xBaxMo2O9−x/2 (x = 0-0.18)

La_2−xBa_xMo₂O_9−x/2 (x ≤ 0.18) have been prepared by solid state reaction method. The lattice parameter of La_2−xBa_xMo₂O_9−x/2 (x ≤ 0.18) determined by XRD data refinement shows a linear dependence on the dopant Ba content x. For the specimen with a La/Ba molar ratio of 0.18-0.2, additional reflection of secondary phase exists in the XRD pattern, so the value of solubility limit for Ba in La₂Mo₂O₉ is defined in range of 0.18 < x < 0.2. As the replacement degree of La³⁺ by Ba²⁺ increases, the bulk conductivity of La_2−xBa_xMo₂O_9−x/2 (x ≤ 0.18) decreases initially and then increases, a minimum value at La_1.9Ba_0.1Mo₂O_8.95 exists. Hebb-Wagner studies in argon atmosphere, which use an oxide-ion blocking electrode, show that La_2−xBa_xMo₂O_9−x/2 (x ≤ 0.18) are predominantly oxide-ion conducting in the temperature ranging from 773 to 1173 K. The average thermal expansion coefficient of La_1.84Ba_0.16Mo₂O_8.92 determined by high-temperature XRD was deduced as great as 17.5 × 10⁻⁶ K⁻¹ between 298 and 1173 K.