Preparation and Characterization of SnS:Bi Thin Films

Thin films based on Sn-S compounds are currently of great interest because of their potential applications in optoelectronic devices including solar cells. In this work, SnS:Bi thin films are prepared using a novel procedure based on sulfurization of their metallic precursors, varying the Bi content. The effect of the synthesis conditions on the optical properties, phase, and chemical composition of the SnS:Bi thin films was studied through spectral transmittance, X-ray diffraction, and X-ray photoelectron spectroscopy. It was established from transmittance measurements that the optical gap of the deposited films varies between 1.27 and 1.37 eV depending on the Bi content. The analysis revealed that the SnS:Bi thin films grow with a mixture of several phases which include SnS, Sn₂S₃ SnS₂, and Bi₂S₃, depending on the Bi concentration. The studies also revealed that the conductivity type of the SnS:Bi films depends on the Bi content in the SnS lattice.     

Photoluminescence, FTIR and X-ray diffraction studies on undoped and Al-doped ZnO thin films grown on polycrystalline α-alumina substrates by ultrasonic spray pyrolysis

Undoped and aluminum-doped zinc oxide (ZnO) thin films have been grown on polycrystalline α-alumina substrates by ultrasonic spray pyrolysis (USP) technique using zinc acetate dihydrate and aluminum chloride hexahydrate (Al source) dissolved in methanol, ethanol and deionized water. A number of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and photoluminescence (PL) were used to characterize the obtained ZnO thin films. It was seen that the orientation changed with increase in substrate temperature. During the ZnO deposition Zn source reacted with polycrystalline α-Al₂O₃ substrate to form an intermediate ZnAl₂O₄ spinel layer. It has been interestingly found that the intensity of green emission at 2.48 eV remarkably increased when the obtained ZnO:Al films were deposited at 380 °C. The FTIR absorbance intensity of spectroscopic band at 447±6 cm⁻¹ is very sensitive to oxygen sublattice disorder resulting from non-stoichiometry, which is consistent with the result of PL characterization.     

Electrodeposition and growth mechanism of SnSe thin films

Tin selenide (SnSe) thin films were electrochemically deposited onto Au(1 1 1) substrates from an aqueous solution containing SnCl₂, Na₂SeO₃, and EDTA at room temperature (25 °C). The electrochemical behaviors and the codeposition potentials of Sn and Se were explored by cyclic voltammetry. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and UV-vis absorption spectroscopy were employed to characterize the thin films. When the electrodeposition potential increased, the Se content in the films decreased. It was found that the stoichiometric SnSe thin films could be obtained at −0.50 V. The as-deposited films were crystallized in the preferential orientation along the (1 1 1) plane. The morphologies of SnSe films could be changed from spherical grains to platelet-like particles as the deposition potential increases. The SEM investigations show that the film growth proceeds via nucleation, growth of film layer and formation of needle-like particles on the overlayer of the film. The optical absorption study showed the film has direct transition with band gap energy of 1.3 eV.     

Effect of deposition time on structural, electrical, and optical properties of SnS thin films deposited by chemical bath deposition

The effect of deposition time on the structural, electrical and optical properties of SnS thin films deposited by chemical bath deposition onto glass substrates with different deposition times (2, 4, 6, 8 and 10 h) at 60 °C were investigated. The obtained films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and optical absorption spectra. All deposited films were polycrystalline and had orthorhombic structure with small crystal grains. Their microstructures had changed with deposition time, and their compositions were nearly stoichiometric. Electrical parameters such as resistivity and type of electrical conduction were determined from the Hall Effect measurements. Hall Effect measurements show that obtained films have p-type conductivity and resistivity values of SnS films have changed with deposition time. For allowed direct, allowed indirect, forbidden direct and forbidden indirect transitions, band gap values varied in the range 1.30-1.97 eV, 0.83-1.36 eV, 0.93-1.49 eV and 0.62-1.23 eV, respectively.     

Electrosynthesis and characterization of Fe doped CdSe thin films from ethylene glycol bath

The CdSe and Fe doped CdSe (Fe:CdSe) thin films have been electrodeposited potentiostatically onto the stainless steel and fluorine doped tin oxide (FTO) glass substrates, from ethylene glycol bath containing (CH₃COO)₂·Cd·2H₂O, SeO₂, and FeCl₃ at room temperature. The doping concentration of Fe is optimized by using (photo) electrochemical (PEC) characterization technique. The deposition mechanism and Fe incorporation are studied by cyclic voltammetry. The structural, surface morphological and optical properties of the deposited CdSe and Fe:CdSe thin films have been studied by X-ray diffraction, scanning electron microscopy (SEM) and optical absorption techniques respectively. The PEC study shows that Fe:CdSe thin films are more photosensitive than that of undoped CdSe thin films. The X-ray diffraction analysis shows that the films are polycrystalline with hexagonal crystal structure. SEM studies reveal that the films with uniformly distributed grains over the entire surface of the substrate. The complete surface morphology has been changed after doping. Optical absorption study shows the presence of direct transition and a considerable decrease in bandgap, E_g from 1.95 to 1.65 eV.     

Characterization and application of cerium fluoride film in infrared antireflection coating

Cerium fluoride (CeF₃) thin films were evaporated to the germanium substrates at different substrate temperature from 100 °C to 250 °C. Structural and optical properties were characterized by X-ray diffraction (XRD), scan electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The morphology of samples deposited at different temperature can be closely related to preferred orientation. The infrared optical constants were obtained by fitting the transmission spectrum using Lorentz oscillator model. A simple example for fabrication of long-wave infrared broadband antireflection coating was also presented.     

Preparation and characterization of electrodeposited Sb2Se3 thin films from non-aqueous media

Semiconducting Sb₂Se₃ thin films have been prepared onto the stainless steel and fluorine doped tin oxide coated glass substrates from non-aqueous media using an electrodeposition technique. The electrodeposition potentials for different bath compositions and concentrations of solution have been estimated from the polarization curves. SbCl₃ and SeO₂ in the volumetric proportion as 1:1 with their equimolar solution concentration of 0.05 M form good quality films. The films are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and optical absorption techniques. The SEM studies show that the film covers the total substrate surface with uneven surface morphology. The XRD patterns of the films obtained by varying compositions and concentrations show that the as-deposited films are polycrystalline with relatively higher grain size for 1:1 composition and 0.05 M concentration. The optical band gap energy for indirect transition in Sb₂Se₃ thin films is found to be 1.195 eV.     

Chemical synthesis of nanocrystalline SnO2 thin films for supercapacitor application

Nanocrystalline SnO₂ thin films were deposited by simple and inexpensive chemical route. The films were characterized for their structural, morphological, wettability and electrochemical properties using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy techniques (SEM), transmission electron microscopy (TEM), contact angle measurement, and cyclic voltammetry techniques. The XRD study revealed the deposited films were nanocrystalline with tetragonal rutile structure of SnO₂. The FT-IR studies confirmed the formation of SnO₂ with the characteristic vibrational mode of Sn-O. The SEM studies showed formation of loosely connected agglomerates with average size of 5-10 nm as observed from TEM studies. The surface wettability showed the hydrophilic nature of SnO₂ thin film (water contact angle 9°). The SnO₂ showed a maximum specific capacitance of 66 F g⁻¹ in 0.5 Na₂SO₄ electrolyte at 10 mV s⁻¹ scan rate.     

Structure, morphology and optical properties of SiO2−x thin films prepared by plasma-assisted pulsed laser deposition

The amorphous silicon oxide SiO_2−x thin films were prepared by the plasma-assisted pulsed laser deposition (PLD) method. X-ray diffraction spectrometry (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-VIS-NIR scanning spectrophotometry and ellipsometry were used to characterize the crystallinity, microscopic morphology and optical properties of obtained thin films. The influences of substrate temperatures, oxygen partial pressures and oxygen plasma assistance on the compositions of silicon oxide (SiO_2−x) thin films were investigated. Results show that the deposited thin films are amorphous and have high surface quality. Stoichiometric silicon dioxide (SiO₂) thin film can be obtained at elevated temperature of 200 °C in an oxygen plasma-assisted atmosphere. Using normal incidence transmittance, a novel and simple method has been proposed to evaluate the value of x in transparent SiO_2−x thin films on a non-absorbing flat substrate.     

Electrodeposition of nanostructured Ni(1−x)Mnx alloys films from chloride bath

NiMn alloys were electrodeposited from chloride bath with various Mn content up to 10 at.%. The effect of bath composition and current density on Mn content of electrodeposited thin films was explored. A maximum of 9.8 at.% Mn content in deposited films was obtained at optimized current density of 40 mA/cm² and MnCl₂/NiCl₂ concentration ratio of 2.5 in the bath. The morphology and crystal structure of deposits were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The constituents in the films were determined by energy dispersive X-ray spectroscopy (EDS). It was revealed that the structure of NiMn coatings had an average grain size of about 17 nm. It was found that the deposits exhibited FCC structure with prefer orientation of <111>. The soft magnetic properties of electrodeposited films were measured by vibrating sample magnetometer (VSM). It was observed that the magnetic parameters such as coercivity and saturation magnetization were decreased with increasing of Mn in the deposits.     

Al2O3 thin films by plasma-enhanced chemical vapour deposition using trimethyl-amine alane (TMAA) as the Al precursor

2 O₃ thin films by plasma-enhanced chemical vapour deposition (PECVD) using trimethyl-amine alane (TMAA) as the Al precursor. The thin films were deposited on both Si and quartz silica (SiO₂) substrates. Deposition rates were typically 60 Å min^-1 keeping the TMAA temperature constant at 45 °C. The deposited Al₂O₃ thin films were stoichiometric alumina with low carbon contamination (0.7–1.3 At%). The refractive index ranged from 1.54 to 1.62 depending on the deposition conditions. The deposition rate was studied as a function of both the RF power and the substrate temperature. The structure and the surface of the deposited Al₂O₃ thin films were studied using X-ray diffraction, atomic force microscopy (AFM) and scanning electron microscopy (SEM). Received: 20 May 1997/Accepted: 12 June 1997     

Effects of the substrate and oxygen partial pressure on the microstructures and optical properties of Ti-doped ZnO thin films

Ti-doped ZnO (ZnO:Ti) thin films were deposited on the glass and Si substrates using radio frequency reactive magnetron sputtering. The effects of substrate on the microstructures and optical properties of ZnO:Ti thin films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and a fluorescence spectrophotometer. The structural analyses of the films indicated that they were polycrystalline and had a hexagonal wurtzite structure on different substrates. When ZnO:Ti thin film was deposited on Si substrate, the film had a c-axis preferred orientation, while preferred orientation of ZnO:Ti thin film deposited on glass substrate changed towards (1 0 0). Finally, we discussed the influence of the oxygen partial pressures on the structural and optical properties of glass-substrate ZnO:Ti thin films. At a high ratio of O₂:Ar of 18:10 sccm, the intensity of (0 0 2) diffraction peak was stronger than that of (1 0 0) diffraction peak, which indicated that preferred orientation changed with the increase of O₂:Ar ratios. The average optical transmittance with over 93% in the visible range was obtained independent of the O₂:Ar ratio. The photoluminescence (PL) spectra measured at room temperature revealed four main emission peaks located at 428, 444, 476 and 527 nm. Intense blue-green luminescence was obtained from the sample deposited at a ratio of O₂:Ar of 14:10 sccm. The results showed that the oxygen partial pressures had an important influence for PL spectra and the origin of these emissions was discussed.     

Catalytic behaviors of ruthenium dioxide films deposited on ferroelectrics substrates, by spin coating process

Catalytic ruthenium dioxide films were deposited by spin-coating process on ferroelectric films mainly constituted of SrBi₂Ta₂O₉ (SBT) and Ba₂NaNb₅O₁₅ (BNN) phases. After thermal treatment under air, these ferroelectric-catalytic systems were characterized by X-ray diffraction and scanning electron microscopy (SEM). SEM images showed that RuO₂ film morphology depended on substrate nature. A study of CH₄ conversion into CO₂ and H₂O was carried out using these catalytic-ferroelectric multilayers: the conversion was analyzed from Fourier transform infrared (FTIR) spectroscopy, at various temperatures. Improved catalytic properties were observed for RuO₂ films deposited on BNN oxide layer.     

The growth mechanism and supercapacitor study of anodically deposited amorphous ruthenium oxide films

In the present study, ruthenium oxide (RuO₂) thin films were deposited on the stainless steel (s.s.) substrates by anodic deposition. The nucleation and growth mechanism of electrodeposited RuO₂ film has been studied by cyclic voltammetry (CV) and chronoamperometry (CA). The deposited films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive analysis by X-rays (EDAX) for structural, morphological, and compositional studies. The electrochemical supercapacitor study of ruthenium oxide thin films have been carried out for different film thicknesses in 0.5 M H₂SO₄ electrolyte. The highest specific capacitance was found to be 1190 F/g for 0.376 mg/cm² film thickness.     

A study of structural, compositional and optical properties of spray-deposited non-stoichiometric (Zn,Fe)S thin films

Non-stoichiometric ternary chalcogenides (Zn,Fe)S were prepared in the film form by pyrolytic spray deposition technique, using air/nitrogen as the carrier gas. The precursor solution comprised of ZnCl₂, FeCl₂ and thiourea. The depositions were carried out under optimum conditions of experimental parameters viz. carrier gas (air/nitrogen) flow rate, concentration of precursor constituents, nozzle substrate distance and temperature of quartz substrate. The deposited thin films were later sintered in argon at 1073 K for 120 min.The structural, compositional and optical properties of the sintered thin films were studied. X-ray diffraction studies of the thin films indicated the presence of (Zn,Fe)S solid solution with prominent cubic sphalerite phase while surface morphology as determined by scanning electron microscopy (SEM) revealed a granular structure.The chemical composition of the resulting thin films as analyzed by energy dispersive X-ray analysis (EDAX) reflected the composition of the precursor solutions from which the depositions were carried out with Fe at% values ranging from 0.4 up to 33.SEM micrographs of thin films reveal that the grain sizes of the thin films prepared using air as carrier gas and N₂ as carrier gas are in the vicinity of 300 and 150 nm, respectively.The diffuse transmittance measurements for thin films, as a function of wavelength reveal the dependence of direct optical band gap on Fe content and type of phase.     

CO sensor derived from mesostructured Au-doped SnO2 thin film

Pure and Au-doped mesostructured SnO₂ thin films were successfully prepared by using non-ionic surfactant Brij-58 (polyoxyethylene acyl ether) as organic template and tin tetrachloride and hydrogen tetrachloroaurate(III) trihydrate as inorganic precursor. Thin films were deposited onto the glass substrates at 450 °C by simple spray pyrolysis technique. The novel mesostructured tin oxide thin films with different Au concentration exhibit highly selective response towards CO. The correlation of the Au incorporation in the mesostructure with particular morphology and gas sensing behavior is discussed using scanning electron microscopy (SEM), X-ray diffraction (XRD), BET surface area and transmission electron microscopy (TEM) studies.     

Studies on the effect of nozzle-to-substrate distance on the structural, electrical and optical properties of spray deposited CdIn2O4 thin films

The physical, chemical, electrical and optical properties of as-deposited and annealed CdIn₂O₄ thin films deposited using spray pyrolysis technique at different nozzle-to-substrate distances are reported. These films are characterized by X-ray diffraction, XPS, SEM, PL, Hall effect measurement techniques and optical absorption studies. The average film thickness lies within 600-800 nm range. The X-ray diffraction study shows that films exhibit cubic structure with orientation along (3 1 1) plane. The XPS study reveals that CdIn₂O₄ films are oxygen deficient. Room temperature PL indicates the presence of green shift with oxygen vacancies. The typical films show very smooth morphology. The best films deposited with optimum nozzle-to-substrate distance (NSD) of 30 cm, has minimum resistivity of 1.3 × 10⁻³ Ω cm and 2.6 × 10⁻⁴ Ω⁻¹ figure of merit. The band gap energy varies from 3.04 to 3.2 eV with change in NSD for annealed films. The effect of NSD as well as the annealing treatment resulted into the improvement of the structural, electrical and optical properties of the studied CdIn₂O₄ thin films.     

Effects of magnesium film thickness and annealing temperature on formation of Mg2Si films on silicon (1 1 1) substrate deposited by magnetron sputtering

Magnesium films of various thicknesses were first deposited on silicon (1 1 1) substrates by magnetron sputtering method and then annealed in annealing furnace filled with argon gas. The effects of the magnesium film thickness and the annealing temperature on the formation of Mg₂Si films were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Mg₂Si thin films thus obtained were found to be polycrystalline and the Mg₂Si (2 2 0) orientation is preferred regardless of the magnesium film thickness and annealing temperature. XRD results indicate that high quality magnesium silicide films are produced if the magnesium/silicon samples are annealed at 400 °C for 5 h. Otherwise, the synthesized films annealed at annealing temperatures lower than 350 °C or higher than 450 °C contain magnesium crystallites or magnesium oxide. SEM images have revealed that microstructure grains in the polycrystalline films are about 1-5 μm in dimensions, and the texture of the Mg₂Si films becomes denser and more homogeneous as the thickness of the magnesium film increases.     

Effect of thickness on the optoelectronic properties of electrodeposited nanostructured SnS films

The present study focuses on the effect of film thickness on the physical properties of tin mono-sulfide (SnS) nanostructures deposited through an electrodeposition technique. The SnS films were characterized using X-ray diffraction (XRD) analysis, which confirmed the formation of polycrystalline orthorhombic SnS thin films. The crystallite size and lattice parameters were estimated from the XRD patterns. The effect of the deposition voltage on the surface morphology of the deposited films was evaluated by field emission electron microscopy (FESEM). The FESEM images revealed that the nanostructures possess plate-like and bulky pyramid morphologies. Also, optical plots of the thin films were considered, which determined the direct band gap energies of the samples as 1.42–1.50 eV. Finally, Mott–Schottky measurements indicated that the samples have p-type conductivity and the carrier concentrations of the SnS films improve with the increase of their thicknesses.     

Electrostatic spray deposition of Gd0.1Ce0.9O1.95 and La0.9Sr0.1Ga0.8Mg0.2O2.87 thin films

The deposition of gadolinia-doped ceria (CGO, Gd_0.1Ce_0.9O_1.95) and LaGaO₃-based perovskite oxides (LSGM, La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.87) thin films on a stainless steel substrate was studied using the electrostatic spray deposition (EDS) technique. The effect of process conditions, such as deposition temperature, deposition time and liquid flow rate, on the surface morphology and microstructure of thin films was examined with scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The deposited CGO films with a highly porous and three-dimensional interconnected structure were obtained at a liquid flow rate of 0.5 ml/h, a deposition temperature of 503 K and a deposition time ranging from 0.5 to 1 h. On the other hand, the deposited LSGM thin films with porous microstructure were also obtained at the deposition time of 1 h, the deposition temperature of 533 K and the liquid flow rate of 0.5 ml/h. The deposited CGO and LSGM thin films were amorphous at the used deposition temperature. Subsequently, the samples were annealed at 1173 K for 2 h and the desired crystal structures were obtained. The chemical analysis of the thin films was investigated by energy dispersive X-ray (EDX) analysis. The observed chemical compositions of the samples were in a fair agreement with those of the starting solutions.