An electrochemical technique to deposit thin films of PbTe

PbTe thin films were deposited electrochemically on transparent conducting oxide coated (TCO) glass substrates from a solution of lead acetate and TeO₂ at low pH. A lead (Pb) strip was used as a sacrificing anode and the TCO glass acted as the cathode, which were short-circuited externally. Depositions were carried out at different temperatures of the bath to study the growth kinetics and grain growth. X-ray diffraction technique, scanning electron microscopy, infrared spectroscopy and resistivity measurements were carried out to characterize the deposited films. The films were polycrystalline in nature with a cubic phase.     

ZnO thin films epitaxially grown by electrochemical deposition method with constant current

The electrochemical deposition (ECD) method is well suited to the preparation of large area devices and has several advantages, although the deposited films have a crystallinity problem. A constant current deposition method was employed for preparation of ZnO thin films in this study, because it was expected that the growth rate of the films could be controlled by means of the current density. The intensity of X-ray diffraction (XRD) peaks, and the size and shape of grains of ZnO films grown on polycrystalline Au substrates were observed to depend on the cathodic current density. On the basis of those results, deposition of ZnO on a Pt layer epitaxially grown on c-sapphire was carried out. The results of ?-scan XRD measurements showed in-plane orientation in agreement with the in-plane direction of the Pt substrate layer, which suggests that the ZnO thin film was epitaxially grown by the ECD method.     

Investigation of electrochemical properties of RuO2 thin films modified by e-beam irradiation

The influence of electron beam irradiation on the electrochemical properties of electrodeposited RuO₂ thin films was investigated using a 1 MeV electron beam. Crystallinity change before and after electron beam irradiation was investigated by X-ray diffraction, and the oxidation state of ruthenium was determined by X-ray photoelectron spectroscopy. Scanning electron microscopy was utilized to examine the morphology of the films. The results show that electron beam irradiation altered the oxidation state of ruthenium and increased crystallinity.Cyclic voltammetry was employed to evaluate the electrochemical properties of the synthesized RuO₂ films in terms of their application as electrodes of electrochemical capacitors. RuO₂ irradiated with 40 kGy showed 2.7 times higher capacitance (520 Fg⁻¹) than the as-electrodeposited sample (190 Fg⁻¹).     

Study of the structural and optical properties of GaPN thin films grown by magnetron RF sputtering

GaP_1−xN_x thin films were deposited on glass substrates by RF sputtering employing a nitrogen-argon atmosphere in a partial pressure of 2×10⁻² Torr. We varied the growth temperature in the range 420-520 °C. The film's optical properties were studied by transmittance and absorbance spectroscopy. Characterization by scanning electron microscopy in cross-sectional view, atomic force microscopy, and X-ray diffraction was performed to determinate the film thickness, surface morphology, and crystal structure, respectively. Raman spectroscopy was employed to analyze the structural properties of samples. The GaP_1−xN_x films presented a cubic polycrystalline structure with a preferential orientation along the [1 1 1] direction. By varying the growth conditions we were able to change the band gap energy between 1.35 and 1.98 eV.     

Tungsten trioxide thin films prepared by electrostatic spray deposition technique

Tungsten trioxide (WO₃) thin films deposited on a Pt-coated alumina substrate using the electrostatic spray deposition (ESD) technique is reported in this paper. As precursor solution, tungsten (VI) ethoxide in ethanol was used. The morphology and the microstructure of the films were studied using scanning electron microscopy coupled with energy dispersive X-ray analysis, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Dense to porous morphologies were obtained by tuning the deposition temperature. Impedance spectroscopy and current-voltage measurements were used to study the electrical behaviour of the films in air, in temperature range 300-500 °C. The activation energy was estimated from Arrhenius plots. Considering the obtained results, the ESD technique proved to be an effective technique for the fabrication of porous tungsten trioxide thin films.     

Tribological application of molecular deposition (MD) films

In this paper, the nanofriction and nanolubrication behaviors of different MD films on the Au substrate were systematically studied. The experimental results indicated that the MD films presented similar nanofriction properties when they had a same terminal. It was also found that the process of the anionning and the depositing of a monolayer MD film on a Au substrate and the process of decorating an alkyl-terminal to MD film surfaces were all capable of lowering the frictional force and improving the nanolubrication property. Moreover, the MD film decorated with alkyl chains had lower frictional forces than the undecorated MD films. Accordingly, it provided us a significant thought to seek for a new nanolubrication film.     

Fabrication of PTFE thin films by dual catalytic chemical vapor deposition method

Dependence of catalyzing materials on deposition of polytetrafluoroethylene (PTFE = ”Teflon” in commercial) films by catalytic chemical vapor deposition (Cat-CVD) method is investigated. It has been clarified that Ni-containing catalyzers has a catalyzing effect that can decompose hexafluoropropylene-oxide (HFPO) to form PTFE films. A novel method named Dual Cat-CVD is also proposed. In the method, carbonized and fluorinated surface of Ni-containing catalyzer is removed and refreshed using atomic hydrogen generated by additionally introduced tungsten (W) catalyzer in the same chamber. This Dual Cat-CVD method enables to recover the deposition rate of PTFE films drastically.     

电泳沉积制备氧化钇稳定的二氧化锆薄膜

采用恒压电泳沉积方法在Ni-YSZ(氧化钇稳定的氧化锆)阳极基体上制备YSZ电解质膜,研究了悬浮体系YSZ含量、外加电压、沉积时间对电泳过程及YSZ膜层质量的影响,结果表明,YSZ含量为20 g/L,沉积电压为10 V,沉积时间5 min时,恒压电泳一次即可得到均匀致密的YSZ膜:膜层与基体结合紧密,厚度约为10 μm.     

Photoelectrochemical and optical properties of N-doped TiO2 thin films prepared by oxidation of sputtered TiNx films

Nitrogen-doped titanium dioxide thin films with visible light photoresponse were prepared by oxidation of sputtered TiN_x films, whose nitrogen contents can be easily changed by controlling the volume ratio of N₂/(Ar + N₂) during reactive direct current (DC) magnetron sputtering process. The reference TiO₂ sample was also deposited by the same method under Ar/O₂ gas mixture. The as-prepared films were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoemission spectroscopy, UV-vis spectrophotometry and photoelecrochemical measurements. The formation of anatase type TiO₂ is confirmed by XRD. SEM measurement indicates a rough surface morphology with sharp, protruding modules after annealing treatment. Optical properties reveal an extended tailing of the absorption edge toward the visible region due to nitrogen presence. The band gap of the N-doped sample is reduced from 3.36 eV to 3.12 eV compared with the undoped one. All the N-doped samples show red shift in photoresponse towards visible region and improved photocurrent density under visible irradiance is observed for the N-doped samples.     

Description of TiO2 thin films treated in NH3 atmosphere by optical dispersion models

The influence of a reductive ammonia atmosphere on TiO₂ sol-gel film structural and optical characteristics was investigated. X-ray Diffraction technique, X-ray photoelectron spectroscopy and Rutherford Back Scattering analysis were applied to study the crystallinity, oxidation state and element concentration profile of the modified films. Their optical properties were investigated by UV-Vis spectroscopy. The refractive index and extinction coefficient were obtained by fitting theoretical transmittance curves to experimental ones using Forouhi-Bloomer (FB) and Tauc-Lorentz (TL) physical models. Both models revealed slight decrease (up to 2.6-2.7 eV) of the FB and TL band gaps with increase of the treatment temperature. These results were discussed in terms of the additional energy levels creation due to the defect TiO₂ structure formation during thermal treatment in reductive atmosphere.     

Fabrication of polymer thin films with in-depth dye-dispersed structures by the vacuum spray method

We report the fabrication of polymer thin films with “in-depth” dye-dispersed structures using a vacuum spray method. Copper (II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine [(t-Bu)₄CuPc] and polycarbonate in chloroform solution were sprayed onto the substrate. The (t-Bu)₄CuPc distribution was controlled precisely during thin film growth by varying its concentration in the solution. Uniform, bilayer, and gradient structures of (t-Bu)₄CuPc dispersed in thin films were confirmed by high-angle annular dark field imaging on scanning transmission electron microscopy. The vacuum spray method has several advantages compared to the casting method, such as smaller dispersed dye-aggregates and lack of cavities due to air bubbles.     

Characterization of metal-supported Al2O3 thin films by scanning electrochemical microscopy

In this paper, physiochemical properties of amorphous alumina thin films, grown by the metal organic chemical vapour deposition process on the surface of platinum (Pt/Al₂O₃) and stainless steel (SS/Al₂O₃), were investigated in aqueous media. The study was performed by the use of scanning electrochemical microscopy (SECM), which allowed obtaining information on uniformity, topography and chemical stability/reactivity of the alumina coatings with high spatial resolution. In particular, the effects due to local acid, base and fluoride ions attack on alumina layers of thickness of about 250 nm (in the Pt/Al₂O₃ sample) and 1000 nm (in the SS/Al₂O₃ sample) were investigated. In the acid and base attack, high concentrations of H₂SO₄ and KOH were electrogenerated locally by the use of a 25 μm diameter platinum microelectrode. The latter was also used as SECM tip to monitor the chemical effect on the alumina layers. It was found that, regardless of the thickness of the film, alumina provided good resistance against local attack of concentrated H₂SO₄; instead, the film dissolved when subjected to KOH attack. The dissolution rate depended on several experimental parameters, such as SECM-tip to substrate distance, electrolysis time and alumina film thickness. The alumina layer proved also relatively poor resistance to etching in 0.1 M NaF solutions.     

A novel patterning technique using super-hydrophobic PTFE thin films by Cat-CVD method

Super-hydrophobic poly-tetrafluoroethylene (PTFE) films, with a water contact angle of over 160°, are formed by catalytic chemical vapor deposition (Cat-CVD) under high catalyzer temperature or pressure. Hydrophobicity of the PTFE films is maintained even after annealing up to 300 °C. We demonstrate a novel method for forming metal lines using super-hydrophobic PTFE films. Water-based functional liquid containing silver nanoparticles dropped on the patterned PTFE film localizes only on hydrophilic regions, resulting in formation of metal lines after annealing up to 150 °C.     

Effect of hydrolysis ratio on structural,optical and electrical properties of SnO2 nanoparticles synthesized by polyol method

Using the polyol method and a thermal post-treatment, nanoporous tin dioxide (SnO₂) were prepared at different hydrolysis ratio (h = n (H₂O)/n (Sn)). The influence of the hydrolysis ratio on the structural, textural, optical and electrical properties of SnO₂ nanopowders was investigated by employing a set of various techniques including Fourier Transform Infra-Red spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM), Nitrogen Sorption Porosimetry and Impedance Spectroscopy. FTIR and EDX studies revealed that SnO₂ species were obtained. Nanocrystallites of cassiterite, i.e. rutile-like tetragonal SnO₂ structure, were formed after annealing in air at 700 °C and the average crystallite size increased from 12.8 to 29.1 when the hydrolysis ratio rose from 17 to 24. Moreover, TEM, SEM, and N₂ sorption porosimetry investigations indicated that the sample prepared for h = 17 was composed of an aggregated network of almost spherical nanoparticles, the morphology and sizes of which changed with the increase in the hydrolysis ratio to h = 24 and the mesoporosity of which was found to be linked to the interparticle space. Moreover, this increase in mean nanoparticle size was accompanied by a decrease in the band gap value from 3.4 eV (h = 17) to 3.16 eV (h = 24). Finally, bulk conductivity dependence with temperature was found to follow an Arrhenius law for samples annealed at 700 °C with an activation energy of 0.65 eV for h = 17, 0.69 eV for h = 20 and 0.71 eV for h = 24 that is typical of SnO₂ nanopowders.     

Characterization of FeS2-pyrite thin films synthesized by sulphuration of amorphous iron oxide films pre-deposited by spray pyrolysis

FeS₂-thin films with good crystallinity were synthesized by a simple method which consists of sulphuration, under vacuum, of amorphous iron oxide thin films pre-deposited by spray pyrolysis of FeCl₃·6H₂O (0.03 M)-based aqueous solution onto glass substrates heated at 350 °C. At optimum sulphuration temperature (450 °C) and duration (6 h), black green layers having granular structure and high absorption coefficient (5.10⁴ cm⁻¹) were obtained. The study of the electrical properties of the as-prepared films vs. the temperature variations showed three temperature domain dependence of the conductivity behaviour. The first one corresponds to the high temperature range (330 K–550 K) for which an Arrhenius plot type was obtained. The activation energy value was estimated at about 61.47 meV. The second domain corresponding to the intermediate temperature range (80 K–330 K) showed a variable activation energy between the grain boundaries. The barrier height, q¯, was estimated to 27±0.5 meV, and the standard deviation, qσ, was evaluated at about 14±0.5 meV. We found that at lower temperatures (20 K–80 K), the conductivity is governed by two conduction types. The density of localised states, was about 2.45×10²⁰ eV⁻¹ cm⁻³.     

Optical and electrical properties of ZnO films, codoped with Al and Ga deposited at room temperature by an RF sputtering method

ZnO thin films, codoped with Al and Ga, were prepared on fused quartz (FQ) and cyclo-olefin polymer (COP) substrates using a radial frequency magnetron sputtering technique at room temperature, without the introducing of oxygen. The elemental distributions of Al, Ga, Zn and O throughout the films were found and no compositional variation in working pressure was observed. A resistivity of 0.03-4.07 Ω cm in AGZ/FQ films (Fig. 2b and 0.04-5.73 Ω cm in AGZ/COP films as well as a transmittance of above 85% were obtained by appropriate control of the working pressure. Compared with the band gap energy of single crystal ZnO, the band gap energy of the AGZ/FQ thin film was somewhat higher. The band gap energy of the AGZ/FQ films showed a tendency to increase with the working pressure employed.     

Fabrication of conducting poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) thin films by ultrasonic spray-assisted mist deposition method

Transparent conducting polymer, poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) thin films were fabricated by a vapor-deposition technique, ultrasonic spray-assisted mist deposition method. The thickness was well controlled from 40 to 600 nm, keeping reasonable conductivity of 300-450 S/cm. The films with thickness less than 180 nm have high (> 80%) transmission over a wide (270-800 nm) spectral region. In addition, formation of ring-dot electrode pattern with a hard-mask was demonstrated, achieving lithography-less patterning. The results encourage that this deposition method is developed as an actual process technology of transparent electrodes in devices.     

Microstructure and thermoelectric properties of p-type Bi-Sb-Te-Se thin films prepared by electrodeposition method

P-type Bi-Sb-Te-Se thermoelectric thin films with thickness of 8 μm have been prepared by cathodic electrodeposition technique on Au substrate from nitric acid solution system at room temperature. Cyclic voltammetry was used for determination of the deposition potentials of the thin films. In order to enhance the crystallinity, as well as the thermoelectric properties of the deposited films, they were annealed at 523 K for 2 h under nitrogen atmospheric pressure condition. X-ray diffraction (XRD), environmental scanning electron microscopy, and energy-dispersive spectroscopy (EDS) were employed to characterize the thin films. Seebeck coefficients and resistivities of the films were also evaluated. The results revealed that Bi, Sb, Te and Se could be co-deposited to form Bi-Sb-Te-Se semiconductor compound in the solution containing Bi^III, Sb^III, Te^IV and Se^IV and the compositions of the films were sensitive to the electrodepositing potentials. The XRD results suggested that the crystal structure of the thin films were changed from amorphous state to polycrystalline after annealing. The EDS data indicated that the composition of the films was consistent with XRD results. The annealed Bi-Sb-Te-Se thin films exhibited the Seebeck coefficients of 116-133 μV/K and a maximum power factor of 0.62 mW·K^− 2·m^− 1.     

Dopamine/TiO2 hybrid thin films prepared by the liquid phase deposition method

Liquid phase deposition method is applied to one-step production of a hybrid material composed by dopamine(DA) and TiO₂ anatase. An optimized amount of the enediol derivative is added to a fluoride titania precursor aqueous solution in order to entrap this modifier within the growing TiO₂, yielding a DA/TiO₂ nanocomposite material. Uniform, well-adhered and brown-colored thin films are deposited on indium tin oxide covered glass substrate. The DA/TiO₂ hybrid material has been characterized by infrared spectroscopy, electronic microscopy, X-ray diffraction and UV-vis spectroscopy. The formation of the hybrid material seems to be reasonably explained by linkage of different TiO₂ nanocrystallites taking advantage of both enediol and amine groups of DA.     

双离子束溅射制备非晶SiOxNy薄膜的强黄光发射

用双离子束溅射法制备了SiOxNy薄膜,并对薄膜的结构和光致发光(PL)性质进行了研究.XRD和TEM的实验结果表明薄膜是非晶结构;用XPS对样品进行了表征,在397.8eV位置处出现一个对应于N1s的对称峰,表明样品中的N原子主要与Si原子结合,FTIR的实验结果也说明了这一点.光吸收测量结果显示SiOxNy薄膜的光学带隙比Si-SiO2薄膜宽.在225nm波长的激发下,测得在590nm处有强的黄光发射,并利用能带模型讨论了可能的发光机制.