Electrical conductivity of nitride carbon films with different nitrogen content

The electrical conductivity of nitride carbon (DLC: N) films has been studied. It is found that the electrical conductivity of the deposited films increases slowly with increasing nitrogen content, however, it decreases after the nitrogen content in the film reaches a certain value of 12.8 at%. Thermal treatment results show that the electrical conductivity of the lowly nitrogen doped DLC film increases rapidly, while that of the heavily doped film decreases after annealing at 300 °C for 30 min. Raman and XPS spectra results show that when the nitrogen content in the films reaches a certain value, there appears nonconductive phases. Therefore the electrical conductivity of the heavily doped films decreases. FTIR spectra analysis results show that the nitrogen atom as an impurity center undergoes an ‘activation’ process during the thermal treatment, which leads to the increase of the electrical conductivity. Therefore, the nitrogen in these two kinds of films has different effects on the electrical conductivity.     

Effect of indium doping on photoelectrochemical properties of Cd0.9Zn0.1Se photosensitive films

Indium doped Cd_0.9Zn_0.1Se films have been synthesized by chemical bath deposition method. The deposited films act as photoanode in photoelectrochemical (PEC) cells. The varying concentration of indium from 0.01 to 1.0 mol% was used. The film thickness increases from 0.72 to 0.80 μm as doping concentration increases up to 0.1 mol%, thereafter it decreases. The cell configuration is n-Cd_0.9Zn_0.1Se:In|NaOH (1 M)+S (1 M)+Na₂S (1 M)|C_(graphite). The various performance parameters were examined with respect to doping concentration of indium. It is found that fill factor and efficiency is maximum for 0.1 mol% indium photosensitive films. This is due to low resistance, high flat band potential, maximum open circuit voltage as well as maximum short-circuit current. The barrier height was examined from the temperature dependence of the reverse saturation current. The lighted ideality factor was found to be minimum for 0.1 mol% indium photosensitive films. A cell utilizing doping photosensitive films showed a wider spectral response. The utility of this work is in improving efficiency of the PEC cell.     

Correlation between the structural and optical properties of Co doped ZnO thin films prepared at different film thickness

Cobalt doped zinc oxide (ZnO:Co) thin films were deposited on glass substrates by ultrasonic spray technique decomposition of Zinc acetate dihydrate and cobalt acetate tetrahydrate in an ethanol solution with film thickness. All films are polycrystalline with a hexagonal wurtzite-type structure with a preferential orientation according to the direction (0 0 2), with the maximum crystallite size was found of 59.42 nm at 569 nm. The average transmittance of all films is about 65–95% measured by UV–vis analyzer. The band gap energy increased from 3.08 to 3.32 eV with increasing the film thickness from 192 to 569 nm. The increase of the electrical conductivity with increases in the film thickness to maximum value of 9.27 (Ω cm)⁻¹ can be explained by the increase in carrier concentration and displacement of the electrons of the films. The correlation between the band gap and crystal structure suggests that the band gap energy of Co doped ZnO is influenced by the crystallite size and the mean strain.     

Characterisation of the anodic layers formed on 2024 aluminium alloy, in tetraborate electrolyte containing molybdate ions

Anodic layer growth on 2024 aluminium alloy at 70 °C, under 40 V, during 60 min, in 50 g L⁻¹ di-sodium tetraborate solution containing di-sodium molybdate from 0.1 to 0.5 M (pH 10) is examined. Anodising behaviours strongly depend on additive concentration. Development of anodic films is favoured with weak molybdate additions (<0.3-0.4 M). The film thicknesses increase and the porosity of anodic layers decreases. Molybdenum (+VI), detected by X-ray photoelectron spectroscopy (XPS) analysis, is present in the anodic films and the Mo incorporation, studied by energy dispersive spectroscopy (EDS) analysis, increases with molybdate concentration. However, for high molybdate concentrations (>0.4 M), anodising behaviour becomes complex with the formation of a blue molybdenum oxide at the cathode. The growth of aluminium oxide is hindered. As the anodic layers are thinner, the Mo(+VI) incorporation significantly decreases. These two configurations implicate different corrosion performances in 5% sodium chloride solution at 35 °C. As the alkaline anodic layer formed with 0.3 M molybdate species is the thickest and the Mo incorporation is the more pronounced, its corrosion resistance is the highest. The effect of morphology and composition of anodic films on pitting corrosion is also discussed.     

Influence of target substrate distance on the properties of transparent conductive Si doped ZnO thin films

Si doped zinc oxide (SZO, Si3%) thin films are grown at room temperature on glass substrates under argon atmosphere, using direct current magnetron sputtering. The influence of the target substrate distances on structure, morphology, optical and electrical properties of SZO thin films is investigated. Experimental results show that the target substrate distances have a significance impact on the growth rate, crystal quality and electrical properties of the films, and have little impact on the optical properties of the films. SZO thin film samples grown on glasses are polycrystalline with a hexagonal wurtzite structure and have a preferred orientation along the c-axis perpendicular to the substrate. When the target substrate distance decreases from 76 to 60 mm, the degree of crystallization of the films increased, the grain size increases, and the resistivity of films decreases. However, when the distance continuously decreases from 60 to 44 mm, the degree of crystallization of the films decreased, the grain size decreases, and the resistivity of the films increases. SZO(3%) thin films deposited at a target substrate distance of 60 mm show the lowest resistivity of 5.53 × 10⁻⁴ Ω cm, a high average transmission of 94.47% in the visible range, and maximum band gap of 3.45 eV under 5 Pa of argon at sputtering power of 75 W for sputtering time of 20 min.     

Synthesis of nano-crystalline zirconium aluminium oxynitride (ZrAlON) composite films by dense plasma Focus device

Zirconium aluminium oxynitride multiphase composite film is deposited on zirconium substrate using energetic nitrogen ions delivered from dense plasma Focus device. X-ray diffractometer (XRD) results show that five Focus shots are sufficient to initiate the nucleation of ZrN and Al₂O₃ whereas 10 Focus shots are sufficient to initiate the nucleation of AlN. XRD results reveal that crystal growth of nitrides/oxides increases by increasing Focus shots (up to 30 Focus shots) and resputtering of the previously deposited film is taken place by further increase in Focus shots (40 Focus shots). Scanning electron microscopic (SEM) results indicate the uniform distribution of spherical grains (∼35 nm). A smoother surface is observed for 20 Focus shots at 0° angular position. SEM results also show a net-type microstructure (thread like features) of the sample treated for 30 Focus shots whereas rough surface morphology is observed for 40 Focus shots. Energy dispersive spectroscopic profiles show the distribution of different elements present in the deposited composite films. A typical microhardness value of the deposited composite films is 5255 ± 10 MPa for 10 grams imposed load which is 3.3 times than the microhardness values of unexposed sample. The microhardness values of the exposed samples increases with increasing Focus shots (up to 30 Focus shots) and decreases for 40 Focus shots treatment due to resputtering of the previously deposited composite film. The microhardness values of the composite films decreases by increasing the sample's angular position.     

Thickness dependence of optoelectrical properties of tungsten-doped indium oxide films

Pulsed laser deposition technique is used for deposition of tungsten-doped indium oxide films. The effect of film thickness on structural, optical and electrical properties was studied using X-ray diffraction (XRD), atomic force microscopy, UV-visible spectroscopy, and electrical measurements. X-ray diffraction study reveals that all the films are highly crystalline and oriented along (2 2 2) direction and the film crystallinity increases with increase in film thickness. Atomic force microscopy analysis shows that these films are very smooth with root mean square surface roughness of ∼1.0 nm. Bandgap energy of the films depends on thickness and varies from 3.71 eV to 3.94 eV. It is observed that resistivity of the films decreases with thickness, while mobility increases.     

Structural characterization and optical properties of UO2 thin films by magnetron sputtering

Uranium dioxide films were deposited on Si (1 1 1) substrates by dc magnetron sputtering method at different sputtering parameters. The structure, morphology and chemical state of the films were studied by field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy. Influences of film thickness on the microstructure and optical properties were investigated. Experimental results show that the film crystallites are preferentially oriented with the (1 1 1) planes. The average grain size increases with increasing film thickness. AFM images show that the root mean square roughness of the films is between 1.2 nm and 2.1 nm. Optical constants (refractive index, extinction coefficient) of the films in the wavelength range of 350-1000 nm are obtained by ellipsometric spectroscopy. The result shows that the refractive index decreases with the increasing film thickness, while extinction coefficient increases with the film thickness.     

Structural and optical characterization of Ce-doped Gd2SiO5 films by sol-gel technique

Cerium-doped Gd₂SiO₅ (GSO:Ce) films have been prepared on (1 1 1) silicon substrates by the sol-gel technique. Annealing was performed in the temperature range from 400 to 1000 °C. X-ray diffraction (XRD), and atomic force microscopy (AFM) were used to investigate the structure and morphology of GSO:Ce films. Results showed that GSO:Ce film starts to crystallize at about 600 °C, GSO:Ce films have a preferential (0 2 1) orientation, as the annealing temperature increase, the (0 2 1) peak intensity increases, the full width of half maximum (FWHM) decreases, and the grain size of GSO:Ce films increases. Emission spectra of GSO:Ce films were measured, results exhibit the characteristic blue emission peak at 427 nm.     

The electrical, optical and magnetic properties of Si-doped ZnO films

In this paper, the influences of Si-doping on electrical, optical and magnetic properties of ZnO films have been systematically investigated. It is found that the resistivity of the films decreases from 3.0 × 10³ to 6.2 × 10^-2 Ωcm with Si-doping due to the increase of carrier concentration. The bandgap of ZnO films increases from 3.28 to 3.52 eV with increasing of Si concentration, which is found to be due to the collective effects of bandgap narrowing and Burstein-Moss effect induced by high carrier concentration. With increase of Si concentration, the near band edge (NBE) emission decreases due to the deterioration of crystal quality, while the yellow emission enhances due to the increase of extrinsic impurity or defects. The additional Si-doping has a profound influence on the enhancement of magnetic property and the maximum magnetic moment of 2.6 μ_B/Si is obtained. The ferromagnetic ordering is seen to be correlated with carrier concentration and structural defects.     

A study on the wet etching behavior of AZO (ZnO:Al) transparent conducting film

This paper studies the wet etching behavior of AZO (ZnO:Al) transparent conducting film with tetramethylammonium hydroxide (TMAH). The optimum optoelectronic film is prepared first using designated RF power, film thickness and controlled annealing heat treatment parameters. The AZO film is then etched using TMAH etchant and AZ4620 photoresist with controlled etchant concentration and temperature to examine the etching process effect on the AZO film optoelectronic properties. The experimental results show TMAH:H₂O = 2.38:97.62 under 45 °C at the average etch rate of 22 nm/min as the preferred parameters. The activation energy drops as the TMAH concentration rises, while the etch rate increases along with the increase in TMAH concentration and temperature. After lithography, etching and photoresist removal, the conductivity of AZO film dramatically drops from 2.4 × 10⁻³ Ω cm to 3.0 × 10⁻³ Ω cm, while its transmittance decreases from 89% to 83%. This is due to the poor chemical stability of AZO film against AZ4620 photoresist, leading to an increase in surface roughness. In the photoresist postbaking process, carbon atoms diffused within the AZO film produce poor crystallinity. The slight decreases in zinc and aluminum in the thin film causes a carrier concentration change, which affect the AZO film optoelectronic properties.     

The influence of substrate temperature variation on tungsten oxide thin film growth in an HFCVD system

Tungsten oxide (WO₃) thin films were deposited by a modified hot filament chemical vapor deposition (HFCVD) technique using Si (1 0 0) substrates. The substrate temperature was varied from room temperature to 430 °C at an interval of 100 °C. The influence of the substrate temperature on the structural and optical properties of the WO₃ films was studied. X-ray diffraction and Raman spectra show that as substrate temperature increases the film tends to crystallize from the amorphous state and the surface roughness decreases sharply after 230 °C as confirmed from AFM image analysis. Also from the X-ray analysis it is evident that the substrate orientation plays a key role in growth. There is a sharp peak for samples on Si substrate due to texturing. The film thickness also decreases as substrate temperature increases. UV-vis spectra show that as substrate temperature increases the film property changes from metallic to insulating behavior due to changing stoichiometry, which was confirmed by XPS analysis.     

Influence of the plasma parameters and nitrogen addition on the electrical characteristics of DLC films deposited by inductively coupled plasma deposition

This work has been based on studies of the plasma parameters influence and nitrogen addition over on the electrical characteristics of diamond-like carbon (DLC) films deposited by inductively coupled plasma deposition (ICP) system. For these studies, it was used a mixture of methane with different flows of nitrogen, two different pressure processes and three different coil powers. The nitrogenated DLC films, had presented a great variation in their electric and structural properties with the nitrogen variation in the plasma. With the nitrogen addition, an increase in its dielectric constant of 1.7-7.4 to concentration of the 40% of the nitrogen has occurred. For high nitrogen concentrations (80% of nitrogen), the dielectric constant decreases (of 7.4 for 5.0). The resistivity of the films decreases with the nitrogen concentration increase (1.2 × 10⁹ Ω cm). Attributing semiconductors characteristics to DLC films. With the increase of nitrogen concentration, the sp³ hybridization increases, too. These characteristics were excellent for innumerable applications in electronic devices.     

Structural, optical and electrical characterization of highly conducting Mo-doped In2O3 thin films

Highly conducting and transparent thin films of molybdenum-doped indium oxide were deposited on quartz by pulsed laser deposition. The effect of growth temperature and oxygen partial pressure on the structural, optical and electrical properties was studied. We find that the film transparency depends on the growth temperature. The average transmittance of the films grown at different temperatures is in range of 48-87%. The X-ray diffraction results show that the films grown at low temperature are amorphous while the films grown at higher temperature are crystalline. Electrical properties are found to be sensitive to both the growth temperature and oxygen pressure. Resistivity of the films decreases from 1.3 × 10⁻³ Ω cm to 8.9 × 10⁻⁵ Ω cm while mobility increases from 9 cm²/V s to 138 cm²/V s as the growth temperature increases from room temperature to 700 °C. However, with increase in oxygen pressure, resistivity increases but the mobility decreases after attaining a maximum. The temperature-dependent resistivity measurements show transition form semiconductor to metallic behavior. The film grown at 500 °C under an oxygen pressure of 1.0 × 10⁻³ mbar is found to exhibit high mobility (250 cm²/V s), low resistivity (6.7 × 10⁻⁵ Ω cm), and relatively high transmittance (∼90%).     

Effect of indium doping in CdO thin films prepared by spray pyrolysis technique

Preparation of transparent and conducting indium doped CdO thin films by spray pyrolysis on glass substrate is reported for various concentration of indium (2-8 wt%) in the spray solution. The electrical, optical and structural properties of indium doped CdO films were investigated using different techniques such as Hall measurement, optical transmission, X-ray diffraction and scanning electron microscope. X-ray analysis shows that the undoped CdO films are preferentially orientated along (2 0 0) crystallographic direction. Increase of indium doping concentration increases the films packing density and reorient the crystallites along (1 1 1) plane. A minimum resistivity of 4.843×10⁻⁴ Ω cm and carrier concentration of 3.73×10²⁰ cm⁻³ with high transmittance in the range 300-1100 nm were achieved for 6 wt% indium doping. The band gap value increases with doping concentration and reaches a maximum of 2.72 eV for 6 wt% indium doping from 2.36 eV of that of undoped film. The minimum resistivity achieved in the present study is found to be the lowest among the reported values for In-doped CdO films prepared by spray pyrolysis method.     

Synthesis of PS colloidal crystal templates and ordered ZnO porous thin films by dip-drawing method

Polystyrene spheres (PS) were synthesized by an emulsifier-free emulsion polymerization technique and the PS colloidal crystal templates were assembled orderly on clean glass substrates by dip-drawing method from emulsion of PS. Porous ZnO thin films were prepared by filling the ZnO sol into the spaces among the close-packed PS templates and then annealing to remove the PS templates. The effects of ZnO precursor sol concentration and dipping time in sol on the porous structure of the thin films were studied. The results showed an ordered ZnO porous thin film with designed pore size that depended on the sol concentration and PS size could be obtained. And the shrinkage of pore diameter was about 30-43%. X-ray diffraction (XRD) spectra indicated the thin film was wurtzite structure. The transmittance spectrum showed that optical transmittance decreased with the decrease of wavelength, but kept above 80% optical transmittances beyond the wavelength of 550 nm. Optical band gap of the porous ZnO thin film (fired at 500 °C) was 3.22 eV.     

The synthesis and kinetic growth of anisotropic silver particles loaded on TiO2 surface by photoelectrochemical reduction method

Silver nanorods with average diameters of 120-230 nm and aspect ratio of 1.7-5.0 were deposited on the surface of TiO₂ films by photoelectrochemical reduction of Ag⁺ to Ag under UV light. The composite films prepared on soda-lime glass substrates were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results show that the TiO₂ film after UV irradiation in AgNO₃ solution is composed of anatase phase TiO₂ and metallic silver with face centered cubic structure. Other compounds cannot be found in the final films. The maximum deposition content of silver particles on the surface of TiO₂ film was obtained with the AgNO₃ concentration of 0.1 M. The kinetic growth rates of silver particles can be controlled by photocatalytic activity of TiO₂ films. The studies suggest that the growth rates of silver particles increase with the enhancement of photocatalytic activity of TiO₂ films. The maximum growth rate of silver particles loaded on TiO₂ films can be up to 0.353 nm min⁻¹ among samples 1#, 2# and 3#, while the corresponding apparent rate constant of TiO₂ is 1.751 × 10⁻³ min⁻¹.     

Morphology of sol-gel produced composite films for optical oxygen sensors

The results reported concern the characterization of thin layer SiO₂-based matrices with an oxygen sensing component Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline) immobilized, when a sol-gel process along with dip- and spin-coating deposition methods are used.SEM, TEM and AFM study, assisted by X-ray energy dispersive microanalysis reveals the influence of the precursors used, sol treatment and the coating conditions on the films morphology and Ru distribution in the matrices. Uniform and smooth surface is produced from tetraethoxysilane (TEOS). The presence of ormosils (methyltriethoxysilane, MtEOS and octyltriethoxysilane, OtEOS) significantly increases the surface roughness exhibited as dots on the SEM image. Their surface concentration and size depend on the number of immersions and withdrawal speed at the dip coating. Spin deposition leads to rather different morphology of the films, based on TEOS/OtEOS. Following commonly used sol preparation procedure (with 1.25-2.5 g Ru-complex/dm³ sol) microcrystallization of the complex occurs with formation of randomly distributed crystals 100-400 nm in size. The ultrasound treatment of the sol by means of ultrasound disintegrator leads to homogeneous distribution of the complex without observable crystallization and significant improvement of the film sensing properties (increase of Stern-Volmer constant and better linearity of the Stern-Volmer plots both in gaseous and aqueous media).     

Effect of substrate temperature on structural, optical and electrical properties of pulsed laser ablated nanostructured indium oxide films

Nanocrystalline indium oxide (INO) films are deposited in a back ground oxygen pressure at 0.02 mbar on quartz substrates at different substrate temperatures (T_s) ranging from 300 to 573 K using pulsed laser deposition technique. The films are characterized using GIXRD, XPS, AFM and UV-visible spectroscopy to study the effect of substrate temperature on the structural and optical properties of films. The XRD patterns suggest that the films deposited at room temperature are amorphous in nature and the crystalline nature of the films increases with increase in substrate temperature. Films prepared at T_s ≥ 473 K are polycrystalline in nature (cubic phase). Crystalline grain size calculation based on Debye Scherrer formula indicates that the particle size enhances with the increase in substrate temperature. Lattice constant of the films are calculated from the XRD data. XPS studies suggest that all the INO films consist of both crystalline and amorphous phases. XPS results show an increase in oxygen content with increase in substrate temperature and reveals that the films deposited at higher substrate temperatures exhibit better stoichiometry. The thickness measurements using interferometric techniques show that the film thickness decreases with increase in substrate temperature. Analysis of the optical transmittance data of the films shows a blue shift in the values of optical band gap energy for the films compared to that of the bulk material owing to the quantum confinement effect due to the presence of quantum dots in the films. Refractive index and porosity of the films are also investigated. Room temperature DC electrical measurements shows that the INO films investigated are having relatively high electrical resistivity in the range of 0.80-1.90 Ωm. Low temperature electrical conductivity measurements in the temperature range of 50-300 K for the film deposited at 300 K give a linear Arrhenius plot suggesting thermally activated conduction. Surface morphology studies of the films using AFM reveal the formation of nanostructured indium oxide thin films.     

Effect of dopant concentration on the properties of HCl-doped PANI thin films prepared at different temperatures

Polyaniline thin film doped with hydrochloric acid (PANI-HCl) has been prepared by chemical oxidative polymerization at three different temperatures (4 °C, 13 °C and 31 °C) with two different dopant concentrations (1 M, 2 M). Fourier transform infrared spectroscopy indicated the presence of dopant and increase in degree of polymerization with decrease in temperature. X-ray diffraction revealed that all the films are of amorphous nature. Scanning electron microscopy showed fiber morphology with high dense inter-fiber fusion. Hall-effect analysis showed that appreciable increase in conductivity of the PANI-HCl films with 2 M-dopant concentration prepared at low temperatures (4 °C, 13 °C) occurs due to increase in carrier concentration. It also indicates the films as P-type semiconductors. UV–vis absorption spectra and photoluminescence spectra revealed that the role of dopant concentration is highly effective in the films prepared at low temperatures. High intense absorption cum emission peaks observed for the films with 2 M dopant concentration prepared at low temperatures is due to the decreased fiber diameter which increased the surface to volume ratio of the fibers and increased localized defect states. Photoluminescence spectra of the films excited using 300 nm show high intense emission peaks at 360 nm, 494 nm and a weak peak at 409 nm confirming the semiconductor nature.