Brush plated ZnS films and their properties

Zinc sulphide thin films were deposited by the brush plating technique using AR grade zinc sulphate and sodium thiosulphate on titanium and conducting glass substrates at a current density of 80 mA cm⁻² and at different deposition temperatures in the range 30–80 °C. The films exhibited cubic structure. Band gap of the films were in the range of 3.79–3.93 eV. Auger spectra of the ZnS films deposited at different current densities indicated that the Zn/S ratio varies in the range of 1.02–1.04. Room temperature PL spectrum of the films deposited at 80 °C indicated two emission peaks at 420 and 480 nm for an excitation of 325 nm. Resistivity of the film varied from 200–769 Ω cm as the deposition temperature increased.     

Morphological, structural, and mechanical characterizations of InGaN thin films deposited by MOCVD

Presented in this study are surface roughness, crystalline structure, and nanomechanical properties of InGaN thin films deposited under various growth temperatures, obtained by means of X-ray diffraction (XRD), atomic force microscopy (AFM), and nanoindentation techniques. The InGaN thin films with different In contents were deposited on sapphire substrates through a metal-organic chemical-vapor deposition (MOCVD) system. Changes in mechanical properties for InGaN thin films are discussed in conjunction with deposition temperature, surface morphology and crystalline structure. The XRD measurements showed that there was no phase separation of In as the In composition went from 25 at.% to 34 at.%. Moreover, both XRD and AFM showed larger grain and surface roughness in In_0.25Ga_0.75N thin films. Nanoindentation results indicate that hardness and Young's modulus both decreased as the indentation depth increased. The contact stress–strain relationships were also analyzed.     

MOCVD of YSZ coatings using β-diketonate precursors

Metallorganic chemical vapor deposition (MOCVD) was investigated as a more efficient means to fabricate yttria-stabilized zirconia (YSZ) for thermal barrier coating. The MOCVD precursors were Y(tmhd)₃ and Zr(tmhd)₄ (tmhd, 2,2,6,6-tetramethyl-3,5-heptanedianato) and delivered via aerosol-assisted liquid delivery (AALD). The maximum YSZ coating rate was 14.2 ± 1.3 μm h⁻¹ at 827 °C yielding a layered coating microstructure. The growth was first-order with temperature below 827 °C with an apparent activation energy of 50.9 ± 4.3 kJ mol⁻¹. Coating efficiency was a maximum of approximately 10% at the highest growth rate. While homogeneous nucleation remained a problem, the deposition of YSZ with only minor carbon content was achieved.     

Growth of HT-LiCoO2 thin films on Pt-metalized silicon substrates

Layered LiCoO2 （HT-LiCoO2） films were grown on Pt-metalized silicon （PMS） substrates and polished bulk nickel （PBN） substrates by pulsed laser deposition. The effects of substrate temperature, oxygen pressure, and substrate surface roughness on the microstructure of LiCoO2 films were investigated. It has been found that a higher substrate temperature and a higher oxygen pressure favor the formation of better crystallized and less lithium-deficient HT-LiCoO2 films. The HT-LiCoO2 film deposited on PBN substrates consists of large randomly orientated equiaxial grains, whereas on PMS substrate, it is made up of loosely packed highly [001] preferential orientated triangular shaped grains with the average grain size less than 100 nm. Electrochemical measurements show that the highly [001] preferentially orientated nanostructured HT-LiCoO2 thin film grown on PMS substrate has good structural stability upon lithium insertion/extraction and can deliver an initial discharge capacity of approximately 45μA·h·cm^-2·μm^-1 with a cycling efficiency of above 99% at the charge/discharge rate of 0.5 C.     

Effect of Ru addition on the properties of Al-doped ZnO thin films prepared by radio frequency magnetron sputtering on polyethylene terephthalate substrate

The addition of ruthenium in aluminum-doped zinc oxide transparent conducting thin films was deposited on polyethylene terephthalate at 20 °C by radio frequency magnetron sputtering technique. The structure and electrical properties of the films were investigated with respect to variation of Ru concentration. The XRD and FESEM results show that the film with 0.5 wt% Ru doping has the best crystallinity and larger pyramid-like grains, therefore the resistivity reached to a lowest value of 9.1 × 10⁻⁴ Ωcm. The low carrier mobilities of the films (3–7.2 cm² V⁻¹ s⁻¹), however, were limited by ionized impurity scattering and grain boundary scattering mechanisms since the carrier concentrations were ranged from 2.2 × 10²⁰ to 9.5 × 10²⁰ cm⁻³. The transmittance in the visible is greater than 80% with the optical band gap in the order of 3.352–3.391 eV.     

Photoluminescence of CdxZn1−xO films grown on sapphire substrate by PLD technique

In this paper, the structural and optical properties of Cd_xZn_1−xO films were studied. The films were deposited by pulse laser deposition (PLD). The Cd concentration was changed in the range from x = 0 to 0.2. The structure of the films was characterized by an atom force microscope (AFM) and X-ray diffraction (XRD). The optical band gap of the films was measured by using transmission and photoluminescence (PL) spectra. The exciton recombination dynamics was investigated by means of the time-resolved photoluminescence (TRPL) spectra of the films at 77 K.     

Role of thermal stability and vapor pressure of bis(2,2,6,6-tetramethyl-3,5-heptanedionato)magnesium(II) and its triamine adduct in producing magnesium oxide thin film using a plasma-assisted LICVD process

Thin films of magnesia were deposited on various substrates using plasma-assisted liquid injection chemical vapor deposition with volatile Mg(tmhd)₂·2H₂O (1) (tmhd = 2,2,6,6-tetramethyl-3,5-heptanedione). The precursor complexes, Mg₂(tmhd)₄·(2), and Mg(tmhd)₂·pmdien (3) (pmdien; N,N,N′,N″,N″-pentamethyldiethylenetriamine) were prepared from Mg(tmhd)₂·2H₂O (1). The temperature dependence equilibrium vapor pressure (p_e)_T data yielded a straight line when log p_e was plotted against reciprocal temperature in the range of 360–475 K, leading to standard enthalpy of vaporization (Δ_vapH°) values of 59 ± 1 and 67 ± 2 kJ mol^− 1 for (2) and (3) respectively. Thin films of magnesium oxide were grown at 773 K using complex (1) on various substrate materials. These films were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray for their composition and morphology.     

Fabricating TiO2 Photocatalysts by rf Reactive Magnetron Sputtering at Varied Oxygen Partial Pressures

Titanium dioxide (TiO₂) thin films were fabricated onto non-alkali glass substrates by rf reactive magnetron sputtering at room temperature using Ti-metal target at varied oxygen partial pressure [O₂/(Ar + O₂)]. The sputtering deposition was performed under an rf power of 200 W. The target to substrate distance was kept at 80 mm, and the total gas pressure was 10 mTorr after 2 h of deposition. It was found that the crystalline structure, surface morphology, and photocatalytic activities of the TiO₂ thin films were affected by the oxygen partial pressure during deposition. The XRD patterns exhibited a broad-hump shape indicating the amorphous structure of TiO₂ thin films. The thin films deposited at a relatively high value of oxygen partial pressure (70%) had a good photo-induced decomposition of methylene blue (MB), photo-induced hydrophilicity, and had a small grain size.     

Preparation of thin film YSZ electrolyte by using electrostatic spray deposition

Yttria-stabilized zirconia (YSZ) thin film was successfully deposited onto Ni–YSZ anode disk by the electrostatic spray deposition (ESD) technique. To deposit a dense YSZ thin film onto porous Ni–YSZ substrate, the influence of process parameter variables were examined. The relationship between process parameters and morphologies of YSZ films coated by ESD was investigated by means of SEM photography and X-ray diffraction (XRD). The result showed that dense YSZ film of average 10–15 μm thickness was deposited on the porous Ni–YSZ substrate with temperature of 400 °C, the precursor solution concentration of 0.05 M, nozzle-to-substrate distance of 30 mm, applied electric field of 18 kV, and deposition time of 90 min.     

Different effects of alkyl sulfate and alkylbenzene sulfonate surfactants on the synthesis and properties of CuPc/TiO2 composite films by the liquid-phase deposition (LPD) method

The insoluble copper phthalocyanine (CuPc)/TiO₂ composite thin film has been successfully prepared in an aqueous solution by liquid-phase deposition (LPD) method, applying two surfactants as the solubilizing agents. The two surfactants are sodium dodecyl benzylsulfonate (SDBS) and sodium lauryl sulfate (SDS), selected as the representative of their groups. The deposited films were characterized by UV–vis, SEM, FT-IR, XRD and ICP–AES. Comparing the two composite thin films, it revealed a series of interesting facts. The films showed excellent adherence to the substrate with particle diameter ranging from 20–50 nm in, and 90 and 280 nm in thickness. It is identified that CuPc is coexisting of dimers and monomers form, mainly in dimeric form for both the composite thin films by UV–vis spectroscopy, illustrating that the CuPc is not further aggregated by LPD process. The dependences of deposited amount of Ti and Cu with the reaction time suggested the growing of the films can be easily controlled, the SDBS seems to be hindrance to the growing of the films. After heat treatment at 250 °C for 2 h, the SDS–CuPc/TiO₂ thin film becomes crystallized, but no obvious XRD peak is observed in the SDBS–CuPc/TiO₂ composite thin film.     

Substrates effect on Zn1−xMnxO thin films grown by RF magnetron sputtering

In this paper, we have presented the surface effect of the substrates on Mn doped ZnO (Zn_1−xMn_xO) thin films grown on Si(1 0 0) and sapphire [i.e. Al₂O₃(0 0 0 1)] by RF magnetron sputtering. These grown films have been characterized by X-ray diffraction (XRD), photoluminescence (PL) and vibrating sample magnetometer (VSM) to know its structural, optical and magnetic properties. All these properties have been found to be strongly influenced by the substrate surface on which the films have been deposited. The XRD results show that the Mn doped ZnO films deposited on Si(1 0 0) exhibit a polycrystalline nature whereas the films on sapphire substrate have only (0 0 2) preferential orientations indicating that the films are single crystalline. The studies of room temperature PL spectra reveal that the Zn_1−xMn_xO/Si(1 0 0) system is under severe compressive strain while the strain is almost relaxed in Zn_1−xMn_xO/Al₂O₃(0 0 0 1) system. It has been observed from VSM studies that Zn_1−xMn_xO/Al₂O₃(0 0 0 1) system shows ferromagnetic nature while the paramagnetic behaviour observed in Zn_1−xMn_xO/Si(1 0 0) system.     

Synthesis and characterization of a series of bis(dimethyl-n-octylsilyl)oligothiophenes for organic thin film transistor applications

A series of bis-dimethyl-n-octylsilyl end-capped oligothiophenes consisting of two to six thiophene units has been synthesized and characterized to develop novel organic semiconductor materials. The UV–vis spectral data indicate that these silyl end-capped oligothiophenes have longer conjugation lengths as evidenced by the higher λ_max values than the corresponding unsubstituted thiophene oligomers. The thermal analyses indicate that the bis-silylated oligothiophenes show lower melting point (DSi-4T = 80 °C; DSi-5T = 115 °C; DSi-6T = 182 °C) than the corresponding dialkylated thiophene oligomers by 100 °C and hexamer DSi-6T exhibits a liquid crystalline mesophase at 143 °C. The α,ω-bis(dimethyl-n-octylsilyl)oligothiophenes (DSi-6T) have a remarkably high solubility in chloroform which are comparable to the corresponding α,ω-dihexyloligothiophenes. The remarkably increased solubility by these silyl end groups leads bis-silylated oligothiophenes to be applicable to solution processable devices for thin film transisitor (TFT) by utilizing a spin-coating technique. α,ω-Bis(dimethyl-n-octylsilyl)sexithiophene can be deposited as active semiconducting layer in thin film transistors, either by vacuum evaporation or by spin-coating. A high charge-carrier mobility has been obtained for both deposition techniques, μ = 4.6 × 10⁻² and 1.4 × 10⁻² cm² V⁻¹ s⁻¹, respectively.     

Mechanisms of films and coatings formation from gaseous and liquid precursors with low pressure plasma spray equipment

Plasma spraying is a well developed and widely used technology, successfully applied for ceramic and metal coatings in many fields of applications such as aeronautics, gas turbine, automotive or medical. The coatings obtained are usually intentionally porous and thick (more than 100 μm). Presently, thin films (< µm) are deposited using various physical vapour deposition (PVD) or chemical vapour deposition (CVD) processes with low deposition rates. In this paper, we make use of the high enthalpy and high ionisation degree of the plasma jet of conventional plasma spraying guns operated at low pressure (mbar) to obtain dense coatings by CVD from gaseous and/or liquid precursors. The advantages of such thermal plasma CVD processes are the high deposition rates to obtain dense and thin layers, and the possibility of combining these thin films with thermally sprayed coatings using the same equipment.An efficient injection and mixing of the liquid and gaseous precursors in the plasma jet, which is especially challenging for liquids in low-pressure processes, has been obtained by extensive developments and proper equipment design. Results of several different coatings based on liquid and gaseous precursors are presented. In particular, SiO_x thin films from HMDSO (Hexamethyldisiloxane, C₆H₁₈OSi₂) precursor and oxygen can be deposited over large areas (50 cm diameter) at typical deposition rates of 35 nm/s, with a precursor-to-film conversion efficiency exceeding 50%. For the case of amorphous carbon deposited from CH₄ or C₂H₄, deposition rates exceeding 25 nm/s are obtained. Results from mass spectrometry of the gas sampled in the plasma jet by an enthalpy probe show that the depletion of hydrocarbon precursors can reach 95% and that higher hydrocarbon species are formed by secondary reactions. In the case of carbon-containing precursors, results from mapping of the optical emission intensity throughout the plasma jet volume are presented. The formation and transport of excited precursor-based species, such as CH, C, C₂, and H are addressed. These results show, in particular, that the very high dissociation efficiency of the precursors takes place through (dissociative) charge exchange from Ar⁺ ions and subsequent dissociative recombination with low energy electrons. The peculiarities of plasma chemistry taking place in the low-pressure plasma jet compared to conventional low-density non-equilibrium plasmas are outlined.     

The role of Mg2Si formation in the hydrogenation of Mg film and Mg nanoblade array on Si substrates

In this paper, both an Mg film and an Mg nanoblade array have been first fabricated directly on Si substrates and hydrogenated under 20 bar hydrogen pressure at temperatures ranging from 200 °C to 350 °C. It is found that Mg₂Si alloy starts to form at T = 200 °C in both the Mg samples, which produces a two-layered structure in the hydrogenated films with the bottom dense layer of Mg₂Si. To prevent Mg alloying with Si, a layer of 200 nm thick Ti film was deposited in between the Mg samples and Si substrates as a diffusion barrier, and their hydrogenation results show that Mg₂Si formation is suppressed greatly and even eliminated in nanoblades, though Mg₂Si hillock defects are observed in the hydrogenated films, which could be formed progressively through the pinholes in the Ti film. To improve the diffusion barrier, a unique structure, consisting of layers of Ti nanorod array and Ti film, has been designed for Mg-based nanostructure deposition. The hydrogen cycling study demonstrates that the structure of 450 nm Ti nanorods on 1 μm Ti film can endure enough number of cycles for the hydrogen storage kinetic and thermodynamic study of film-based Mg nanostructures with/without nanocatalyst, and thus one can gain a fundamental understanding of hydrogen interacting with Mg intrinsic nanostructures and nanocatalysts.     

Influence of excitation frequency on structural and electrical properties of spray pyrolyzed CuInS2 thin films

This paper reports the cost effective deposition of the copper indium sulfide (CuInS₂) thin films under atmospheric conditions via ultrasonic spray pyrolysis. Structural and electrical properties of these films have been tailored by controlling the nozzle excitation frequency and the solution loading. Smoother films have been obtained via 120 kHz excitation frequency compare to the 48 kHz. Band gap energy of the films has also been tailored via excitation frequency. UV–vis–NIR analysis revealed that films deposited at 48 kHz excitation frequency had lower band gap energies. Although, both excitation frequencies resulted chalcopyrite structure, crystallinity of the CuInS₂ films was better for 120 kHz. On the other hand, better optical absorption in visible and near infrared region was observed at 48 kHz. Moreover, room temperature electrical conductivity of the samples deposited at 48 kHz excitation frequency was higher than that of samples deposited at 120 kHz. Temperature dependent electrical conductivity data showed that variable range hopping mechanism can be used to explain the conduction of spray pyrolyzed CuInS₂ thin films. Electrical mobility as high as 48 cm²/Vs has been observed for the sample deposited from 0.51 ml/cm² loading at 48 kHz excitation frequency. This value is very close to the mobility of vacuum deposited thin films like amorphous silicon, which is one of the most commonly used semiconductor in electronic and energy applications.     

Elaboration and characterization of nanocrystalline TiO2 thin films prepared by sol–gel dip-coating

Nanocrystalline TiO₂ thin films were deposited on a ITO coated glass substrate by sol–gel dip coating technique, the layers undergo a heat treatment at temperatures varying from 300 to 450 °C. The structural, morphological and optical characterizations of the as deposited and annealed films were carried out using X-ray diffraction (XRD), Raman spectroscopy, Atomic Force Microscopy (AFM), visible, (Fourier-Transform) infrared and ultraviolet spectroscopy, Fluorescence and spectroscopic ellipsometry. The results indicate that an anatase phase structure TiO₂ thin film with nanocrystallite size of about 15 nm can be obtained at the heat treatment temperature of 350 °C or above, that is to say, at the heat treatment temperature below 300 °C, the thin films grow in amorphous phase; while the heat treatment temperature is increased up to 400 °C or above, the thin film develops a crystalline phase corresponding to the titanium oxide anatase phase. We have accurately determined the layer thickness, refractive index and extinction coefficient of the TiO₂ thin films by the ellipsometric analysis. The optical gap decreases from 3.9 to 3.5 eV when the annealing temperature increases. Photocatalytic activity of the TiO₂ films was studied by monitoring the degradation of aqueous methylene blue under UV light irradiation and was observed that films annealed above 350 °C had good photocatalytic activity which is explained as due to the structural and morphological properties of the films.     

Characteristics of copper oxide films deposited by PBII&D

Copper oxide films were deposited by plasma based ion implantation and deposition using a copper antenna as rf sputtering ion source. A gas mixture of Ar + O₂ was used as working gas. During the process, copper that was sputtered from the rf antenna reacted with oxygen and was deposited on a silicon substrate. The composition and the chemical state of the deposited films were analyzed by XPS. The structure of the films was detected by XRD. It is observed that Cu₂O film has been prepared on the Si substrate. It is found that the microstructure of the deposited film is amorphous for the applied voltage of − 5 kV. The surface layer of the deposited films is CuO. This is because the surface layer absorbs the oxygen from ambient air after the treated sample was removed from the vacuum chamber. An appropriate applied voltage, 2 kV under the present conditions, brings the lowest resistance. It is also seen that the maximum absorbance of the deposited films moves to a lower wavelength with increased applied voltage.     

Effect of quenching on magnetostriction and microstructure of melt-spun Fe83Ga17 alloy

The effect of quenching on magnetostriction and microstructure of melt-spun Fe₈₃Ga₁₇ ribbons was investigated. The results show that magnetostriction of ribbons is greatly improved by heat treatment and the value of λ of ribbons reached nearly −2300 ppm after annealed at 700 °C for 3 h. The XRD analyses reveal that the microstructure of melt-spun Fe₈₃Ga₁₇ alloy ribbons was changed after heat treatment and the transition of A2 + DO₃ → A2 + DO₃ + DO₁₉ occurred at 700 °C for the ribbons. The magnetostriction of Fe₈₃Ga₁₇ ribbons is influenced by the emergence of DO₁₉ structure and the increase of ordered degree, and the variation of crystallinity of A2 phase is also related to the magnetostriction of Fe₈₃Ga₁₇ ribbons.     

Technology of metal oxide thin film deposition with interruptions

The idea to obtain metal-oxide films with small grain size is to use a special regime of thin film deposition by r.f. sputtering of pure metal or metal oxide targets. This regime includes the deposition of thin films with one or several interruptions during the deposition process. WO₃ films were r.f. sputtered onto pure and oxidized silicon wafers. Four types of films were prepared, i.e. using continual deposition, one, two and three interrupted depositions with an actual deposition time of 40 min. The interruption time changed from 0.5 min to 5.0 min for the different samples. It was found that the total thickness of WO₃ films decreased with the increase of the number of interruptions and the increase in interruption time. Phase composition and features of surface morphology of the films deposited and annealed in the temperature range from room temperature to 900 °C have been investigated by XRD and AFM, respectively. It is shown that grain size in the metal oxide films decreased essentially with the increase of the number of interruption during the deposition process.     

Deposition of SDC and NiO-SDC thin films and their surface morphology control by electrostatic spray deposition

The deposition of samaria-doped ceria (SDC, Sm_0.2Ce_0.8O_x) and NiO-SDC thin films on a SDC substrate was studied using the electrostatic spray deposition (ESD) technique. The precursor solution was prepared by dissolving the correct amount of Sm(NO₃)₃·6H₂O, Ce(NO₃)₃·6H₂O and Ni(NO₃)₂·6H₂O into a mixture of ethanol (C₂H₅OH) and butyl carbitol (C₄H₉OC₂H₄OC₂H₄OH). The surface microstructure of as-deposited thin films was strongly influenced by the substrate temperature, solvent composition and precursor solution. The reticular film of SDC with high porosity could be successfully prepared at the deposition temperature ranging from 300 to 350 °C, a precursor solution of 0.005 mol/dm³ and a 50 vol.% of butyl carbital. The correlations between the surface morphology of as-deposited thin films and the physical properties of precursor solution could be approximately explained by the following equation [21]:

where d is the size of sprayed droplet, Q the flow rate of liquid pushed through the jet, the dielectric constant of liquid, ₀ the electrical permittivity of vacuum, and G() is the function of .The as-deposited thin films were amorphous at the used deposition temperature (350 °C). Subsequently, the thermal treatments were done for ranging from 700 to 900 °C in air. As the result, the crystal structure transformed into the desired cubic fluorite one after the sample was annealed over 700 °C in the as-deposited SDC thin films and 900 °C in the as-deposited NiO-SDC thin films, respectively. To confirm the composition of the as-sintered SDC thin films, ICP-OES analysis was studied for the films annealed at 900 °C in air for 2 h. The observed chemical composition was found to be close to that of the precursor solution within experimental errors.