Fabrication of ZnO thin films by the photochemical deposition method

ZnO thin films were fabricated by the photochemical deposition (PCD) method. The deposition solution contains ZnSO₄, Na₂SO₃, Na₂S₂O₃ and a small amount of NH₄OH for pH adjustment. We blew oxygen or oxygen + ozone (O₃) gas into the solution to increase the dissolved oxygen content and enhance the oxidation reaction. The films were characterized by Auger electron and optical spectroscopy, and a photoelectrochemical (PEC) measurement. On an indium-tin-oxide (ITO) substrate, the films showed high optical transmission in the visible range. In a current-voltage measurement for films on a p-Si substrate, the O₃ bubbling sample showed rectification properties and photovoltaic effects.     

Enhanced electrochromism in cerium doped molybdenum oxide thin films

Cerium (5-15% by weight) doped molybdenum oxide thin films have been prepared on FTO coated glass substrate at 250 °C using sol-gel dip coating method. The structural and morphological changes were observed with the help of XRD, SEM and EDS analysis. The amorphous structure of the Ce doped samples, favours easy intercalation and deintercalation processes. Mo oxide films with 10 wt.% of Ce exhibit maximum anodic diffusion coefficient of 24.99 × 10⁻¹¹ cm²/s and the change in optical transmittance of (ΔT at 550 nm) of 79.28% between coloured and bleached state with the optical density of (ΔOD) 1.15.     

Nitriding of titanium by NH3 RF plasma: a study of the corrosion resistance and the mechanical properties of the protective films formed at the solid surface

The exposure of a titanium sample to an NH₃ low pressure plasma leads to the formation of a nitriding layer. The products formed at the titanium surface were identified by XRD spectroscopy. The modification of the corrosion resistance characteristics of titanium due to the NH₃ plasma treatment were investigated by electrochemical tests. The recorded polarization curves of the treated titanium samples were used to determine the values of the corrosion potential E_corr. This study confirms the increasing of the corrosion resistance as a function of the time exposure and the injected electric power in the silica reactor. The plasma treatment also induces drastic changes of the titanium target in hardness.     

Large-area SnO2: F thin films by offline APCVD

In this paper, we reported the successful preparation of fluorine-doped tin oxide (FTO) thin films on large-area glass substrates (1245 mm × 635 mm × 3 mm) by self-designed offline atmospheric pressure chemical vapor deposition (APCVD) process. The FTO thin films were achieved through a combinatorial chemistry approach using tin tetrachloride, water and oxygen as precursors and Freon (F-152, C2H4F2) as dopant. The deposited films were characterized for crystallinity, morphology (roughness) and sheet resistance to aid optimization of materials suitable for solar cells. We got the FTO thin films with sheet resistance 8-11 Ω/□ and direct transmittance more than 83%. X-ray diffraction (XRD) characterization suggested that the as-prepared FTO films were composed of multicrystal, with the average crystal size 200-300 nm and good crystallinity. Further more, the field emission scanning electron microscope (FESEM) images showed that the films were produced with good surface morphology (haze). Selected samples were used for manufacturing tandem amorphous silicon (a-Si:H) thin film solar cells and modules by plasma enhanced chemical vapor deposition (PECVD). Compared with commercially available FTO thin films coated by online chemical vapor deposition, our FTO coatings show excellent performance resulting in a high quantum efficiency yield for a-Si:H solar cells and ideal open voltage and short circuit current for a-Si:H solar modules.     

Optical properties of nanocrystalline SnS2 thin films

Thin films of nanocrystalline SnS₂ on glass substrates were prepared from solution by dip coating and then sulfurized in H₂S (H₂S:Ar = 1:10) atmosphere. The films had an average thickness of 60 nm and were characterized by X-ray diffraction studies, scanning electron microscopy, EDAX, transmission electron microscopy, UV-vis spectroscopy, and Raman spectroscopy. The influence of annealing temperature (150-300 °C) on the crystallinity and particle size was studied. The effect of CTAB as a capping agent has been tested. X-ray diffraction analysis revealed the polycrystalline nature of the films with a preferential orientation along the c-axis. Optical transmission spectra indicated a marked blue shift of the absorption edge due to quantum confinement and optical band gap was found to vary from 3.5 to 3.0 eV with annealing temperature. Raman studies indicated a prominent broad peak at ∼314 cm⁻¹, which confirmed the presence of nanocrystalline SnS₂ phase.     

Preparation of LiMn2O4 thin films by aqueous solution deposition

Cathode material LiMn₂O₄ thin films were prepared by aqueous solution deposition using lithium acetate and manganese acetate as starting materials. The structures, morphologies, and the first discharge specific capacity of the thin films were investigated as a function of annealing temperature and time. The cycling properties of the thin films were also examined. The results show that LiMn₂O₄ thin films prepared by this method are homogenous and crack-free. The thin film annealed at 750°C for 30 min has good rechargeability. The capacity loss per cycle is about 0.05% after being cycled 100 times.     

Fractal nature of crystalline-crystalline interface in CuInSe2 thin films

The characteristics of sub-micron scale crystalline-crystalline interface roughness in CuInSe₂ thin films have been studied using transmission electron microscopy. The interface is formed by local recrystallization of CuInSe₂ films using electron beam irradiation in a transmission electron microscope. Analysis of the interface data obtained from the electron micrographs suggested that the interface shows self-affine fractal scaling with a static scaling exponent of 0.97±0.02.     

Substrate temperature effects on the growth and properties of γ-MnS thin films grown by rf sputtering

The growth of manganese(II) sulfide films by radiofrequency sputtering are shown for the first time. Polycrystalline, nearly stoichiometric films of the metastable hexagonal γ-MnS phase were obtained when the substrate temperature was approximately 26°C. For higher substrate temperatures, 120 and 180°C, the films were amorphous and sulfur deficient. The sulfur loss is substrate-temperature dependant. This behavior is discussed in terms of the dissociation of the MnS molecules during the sputtering process and the phase diagram of sulfur. An analysis of the optical transmission spectrum of the γ-MnS films allowed us to estimate their index of refraction in the non-absorbing region of the spectrum and the electronic band gap in the high absorbance region, obtaining an E_g value of 3.47±0.01 eV at room temperature.     

Photoelectrochemical and physical properties of tungsten trioxide films obtained by aerosol pyrolysis

Aerosol pyrolysis (AP) was used for preparing semiconducting films of tungsten trioxide using peroxotungstic acid as a precursor. The films were characterized by SEM, XRD, and by their photoelectrochemical response. Porous, polycrystalline (monoclinic) films of thickness up to 3 μm were prepared. An incident photon to current efficiency (IPCE) of 0.55 at 365 nm was obtained for films of 1 μm thickness on conducting F:SnO₂/glass substrates under depletion conditions, in junctions with aqueous electrolytes. The spectral (photocurrent) response extended into the visible region (up to 470 nm) which is of importance for solar applications like photocatalysis.     

A simple chemical method for deposition of electrochromic Prussian blue thin films

This paper is about a recently developed new chemical method for deposition of Prussian blue thin films. The films are easily prepared by successive immersion of the substrates into an acidic aqueous solution of Fe₂(SO₄)₃ and K₄[Fe(CN)₆]. It is calculated of the results from AFM analysis that the growth in the film thickness by one immersion cycle corresponds to an average increase of 6 nm. The characterization of the films with X-ray diffraction, SEM-EDS analysis and FTIR spectroscopy shows that the deposited material is amorphous hydrated Fe₄[Fe(CN)₆]₃. The electrochromic properties are characterized by cyclic voltammetry and VIS spectrophotometry. The PB thin films exhibit stability and excellent reversibility, which make these films favorable for electrochromic devices.     

Fabrication of luminescent SrWO4 thin films by a novel electrochemical method

Highly crystallized SrWO₄ thin films with single scheelite structure were prepared within 60 min by a cell electrochemical method. X-ray diffraction analysis shows that SrWO₄ thin films have a tetragonal structure. Scanning electron microscopy examinations reveal that SrWO₄ grains grow well in tetragonal tapers and grains like flowers or bunches, which can usually form by using the electrolysis electrochemical method, have disappeared under cell electrochemical conditions. X-ray photoelectron spectra and energy dispersive X-ray microanalysis examinations demonstrate that the composition of the film is consistent with its stoichiometry. These SrWO₄ films show a single blue emission peak (located at 460 nm) using an excitation wave of 230 nm. The speed of cell electrochemical method can be controlled by changing temperature. The optimum treatment temperature is about 50-60 °C.     

High roughness Ag back reflector on a metal underlayer for thin film solar cell applications

The roughness development of Ag film was investigated for potential as a back reflector material in thin film solar cells on flexible stainless steel (STS) substrates. The influence of metal underlayers was evaluated in order to obtain a rough Ag film at a low deposition temperature (≤400 °C). By depositing Ag on a 100 nm Al underlayer to induce Ag–Al alloying, the film roughness was increased three times more than that of Ag films on bare STS at 400 °C. The Ag film deposited on an Al underlayer at 350 °C exhibited 75 nm roughness and uniformly distributed crystallites, which was effective for visible light scattering. The Ag–Al alloy phase was also controlled using the thickness ratio of Ag and Al. The present work clearly demonstrated that an Ag back reflector film with a higher roughness could be fabricated through inserting a metal underlayer at a deposition temperature much lower than the 500 °C that has been reported in earlier works.     

Preparation and super-hydrophilic properties of TiO2/SnO2 composite thin films

SnO₂-TiO₂ composite thin films were fabricated on soda-lime glass with sol-gel technology. By measuring the contact angle of the film surface and the degradation of methyl orange, we studied the influence of SnO₂ doping concentration, heat-treatment temperature and film thickness on the super-hydrophilicity and photocatalytic activity of the composite films. The results indicate that the doping of SnO₂ into TiO₂ can improve their hydrophilicity and photocatalytic activity, and the composite film with 1-5 mol% SnO₂ and heat-treated at 450°C is of super-hydrophilicity. The optimal SnO₂ concentration for the photocatalytic activity is 10 mol% and larger film thickness is helpful to reduce the contact angle of the composite films.     

MoS2 nanosheet functionalized with Cu nanoparticles and its application for glucose detection

For the first time, Cu nanoparticles were evenly decorated on MoS₂ nanosheet by chemical reduction. The as-prepared Cu-MoS₂ hybrid was characterized by atomic force microscope (AFM), Raman spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and then used to fabricate a non-enzymatic glucose sensor. The performance of our sensor was investigated by cyclic voltammetry and amperometric measurement in alkaline media. Electrochemical tests showed that Cu-MoS₂ hybrid exhibited synergistic electrocatalytic activity on the oxidation of glucose with a high sensitivity of 1055 μA mM⁻¹ cm⁻² and a linear range up to 4 mM.     

Preparation and characterization of spray deposited n-type WO3 thin films for electrochromic devices

The n-type tungsten oxide (WO₃) polycrystalline thin films have been prepared at an optimized substrate temperature of 250 °C by spray pyrolysis technique. Precursor solution of ammonium tungstate ((NH₄)₂WO₄) was sprayed onto the well cleaned, pre-heated fluorine doped tin oxide coated (FTO) and glass substrates with a spray rate of 15 ml/min. The structural, surface morphological and optical properties of the as-deposited WO₃ thin films were studied. Mott-Schottky (M-S) studies of WO₃/FTO electrodes were conducted in Na₂SO₄ solution to identify their nature and extract semiconductor parameters. The electrochromic properties of the as-deposited and lithiated WO₃/FTO thin films were analyzed by employing them as working electrodes in three electrode electrochemical cell using an electrolyte containing LiClO₄ in propylene carbonate (PC) solution.     

Preparation and characterization of amorphous manganese sulfide thin films by SILAR method

Manganese sulfide thin films were deposited by a simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method using manganese acetate as a manganese and sodium sulfide as sulfide ion sources, respectively. Manganese sulfide films were characterized for their structural, surface morphological and optical properties by means of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and optical absorption measurement techniques. The as-deposited film on glass substrate was amorphous. The optical band gap of the film was found to be thickness dependent. As thickness increases optical band gap was found to be increase. The water angle contact was found to be 34°, suggesting hydrophilic nature of manganese sulfide thin films. The presence of Mn and S in thin film was confirmed by energy dispersive X-ray analysis.     

The solution growth route and characterization of electrochromic tungsten oxide thin films

Electrochromic tungsten oxide thin films were prepared by using an aqueous solution of Na₂WO₄·2H₂O and dimethyl sulfate. Various techniques were used for the characterization of the films such as X-ray diffraction, cyclic voltammetry, SEM analysis and VIS-spectroscopy. The thin film durability was tested in an aqueous solution of LiClO₄ (0.1 mol/dm³) for about 7000 cycles followed by cyclic voltammetry. No significant changes in the cyclic voltammograms were found, thus proving the high durability of the films.The optical transmittance spectra of coloured and bleached states showed significant change in the transmittance, which makes these films favorable for electrochromic devices.     

The fractal study of Cu-Ni layer accumulation during electrodeposition under diffusion-controlled condition

The fractal study of thin layer films has been concerned by numerous studies, but it is a novel idea to use this method for interpretation of layer formation during electrocrystallization, simultaneously. In present study, Scharifker's equations were derived for instantaneous and progressive nucleation and 3D growth of hemispherical centers under diffusion-controlled condition to calculate in situ change of fractal dimension of surface. It was assumed that the layer could be formed completely when fractal dimension of surface inclined to 2. Moreover, the fractal analysis of AFM images has confirmed the presumed model.     

A study of structural transition in nanocrystalline titania thin films by X-ray diffraction Rietveld method

Structural and microstructural analyses of nanocrystalline titania thin films prepared by pulsed laser deposition have been carried out. At lower oxygen partial pressures (≤10⁻⁴ mbar), rutile films were formed, whereas at 1.2 × 10⁻³ mbar of oxygen partial pressure, the thin films contained both rutile and anatase phases. At 0.04 and 0.05 mbar of oxygen partial pressure, the film was purely anatase. Addition of oxygen has also shown a profound influence on the surface morphology of the as deposited titania films. Modified Rietveld method has been used to determine crystallite size, root mean square strain and fractional coordinates of oxygen of the anatase films. The influence of crystallite size and strain on the rutile to anatase phase transition is investigated.