Characterization of gallium-doped CdS thin films grown by chemical bath deposition

Ga-doped CdS thin films, with different [Ga]/[Cd] ratios, were grown using chemical bath deposition. The effect of Ga-doping on optical properties and bandgap of CdS films is investigated. Resistivity, carrier density, and mobility of doped films were acquired using Hall effect measurements. Crystal structure as well as crystal quality and phase transition were determined using X-ray diffraction (XRD) and Micro-Raman spectroscopy. Film morphology was studied using scanning electron microscopy, while film chemistry and binding states were studied using X-ray photoelectron spectroscopy (XPS). A minimum bandgap of 2.26 eV was obtained at [Ga]/[Cd] ratio of 1.7 × 10⁻². XRD studies showed Ga³⁺ ions entering the lattice substitutionally at low concentration, and interstitially at high concentration. Phase transition, due to annealing, as well as induced lattice defects, due to doping, were detected by Micro-Raman spectroscopy. The highest carrier density and lowest resistivity were obtained at [Ga]/[Cd] ratio of 3.4 × 10⁻². XPS measurements detect an increase in sulfur deficiency in doped films.     

Physical properties of ZnS thin films prepared by chemical bath deposition

Zinc sulphide thin films are deposited on SnO₂/glass using the chemical bath deposition technique. X-ray diffraction and atomic force microscopy are used to characterize the structure of the films; the surface composition of the films is studied by Auger electrons spectroscopy, the work function and the photovoltage are investigated by the Kelvin method. Using these techniques, we specify the effect of pH solution and heat treatment in vacuum at 500 °C. The cubic structure corresponding to the (1 1 1) planes of β-ZnS is obtained for pH equal to 10. The work function (Φ_material − Φ_probe) for ZnS deposited at pH 10 is equal to −152 meV. Annealing at 500 °C increases Φ_m (by about 43 meV) and induces the formation of a negative surface barrier. In all cases, Auger spectra indicate that the surface composition of zinc sulphide thin films exhibits the presence of the constituent elements Zn and S as well as C and O as impurity elements.     

Bismuth oxide thin films prepared by chemical bath deposition (CBD) method: annealing effect

Bismuth oxide thin films have been deposited by room temperature chemical bath deposition (CBD) method and annealed at 623 K in air. They were characterized for structural, surface morphological, optical and electrical properties. From the X-ray diffraction patterns, it was found that after annealing a non-stoichiometric phase, Bi₂O_2.33, was removed and phase pure monoclinic Bi₂O₃ was obtained. Surface morphology of Bi₂O₃ film at lower magnification SEM showed rod-like structure, however, higher magnification showed a rectangular slice-like structure perpendicular to substrate, giving rise to microrods on the surface. The optical studies showed the decrease in band gap by 0.3 eV after annealing. The electrical resistivity variation showed semiconductor behavior and from thermoemf measurements, the electrical conductivity was found to be of n-type.     

Properties of In2S3 thin films deposited onto ITO/glass substrates by chemical bath deposition

In₂S₃ films have been chemically deposited on ITO coated glass substrates by chemical bath deposition, using different deposition times and precursor concentrations. The bilayers are intended for photovoltaic applications. Different characterization methods have been employed: optical properties of the films were investigated from transmittance measurements, structural properties by XRD and micro-Raman, and surface morphology by SEM microscopy analysis. Also, the direct and indirect band-gaps and the surface gap states were studied with surface photovoltage spectroscopy (SPS). We proposed that electronic properties of the In₂S₃ samples are controlled by two features: shallow tail states and a broad band centred at 1.5 eV approximately. Their relation with the structure is discussed, suggesting that their origin is related to defects created on the S sub-lattice, and then both defects are intrinsic to the material.     

Evolution of structural and optical properties of rutile TiO2 thin films synthesized at room temperature by chemical bath deposition method

Nanocrystalline thin films of TiO₂ were prepared on glass substrates from an aqueous solution of TiCl₃ and NH₄OH at room temperature using the simple and cost-effective chemical bath deposition (CBD) method. The influence of deposition time on structural, morphological and optical properties was systematically investigated. TiO₂ transition from a mixed anatase–rutile phase to a pure rutile phase was revealed by low-angle XRD and Raman spectroscopy. Rutile phase formation was confirmed by FTIR spectroscopy. Scanning electron micrographs revealed that the multigrain structure of as-deposited TiO₂ thin films was completely converted into semi-spherical nanoparticles. Optical studies showed that rutile thin films had a high absorption coefficient and a direct bandgap. The optical bandgap decreased slightly (3.29–3.07 eV) with increasing deposition time. The ease of deposition of rutile thin films at low temperature is useful for the fabrication of extremely thin absorber (ETA) solar cells, dye-sensitized solar cells, and gas sensors.     

Improved dielectric properties of (Pb,Ca)TiO3 thin films prepared by metal-organic decomposition method

(Pb,Ca)TiO₃ (PCT) thin films have been deposited on Pt/Ti/SiO₂/Si substrate by metal-organic decomposition (MOD) technique. The film processing parameters such as drying and annealing temperatures have been optimized to obtain good-quality PCT films. Compositional analysis of the film has been studied by X-ray photoelectron spectroscopy (XPS). The effect of the annealing temperature on the crystalline structure, microstructure and electrical properties have been investigated by X-ray diffraction, atomic force microscopy (AFM) and impedance analyzer, respectively. Amorphous PCT films form at 350 °C and crystallize in the perovskite phase following the isothermal annealing at ?650 °C for 3 h in oxygen ambient. Typical tetragonal structure of the PCT film is evidenced from X-ray diffraction pattern. The grain size in the PCT films increases with an increase in annealing temperature. Significant improvement in the dielectric constant value is observed as compared to other reported work on PCT films. The observed dielectric constant and dissipation factor at 100 kHz for 650 °C annealed PCT films are 308 and 0.015, respectively. The correlation of the film microstructural features and electrical behaviors is described.     

Synthesis of CuS thin films by microwave assisted chemical bath deposition

In this study, oriented CuS nanoplates standing perpendicularly on F: SnO₂ (FTO) coated glass substrates have been prepared through a mild microwave assisted chemical bath deposition process in which copper acetate reacted with ethylenediamine tetraacetate acid disodium and thioacetamide in aqueous solution within 40 min. The effects of reaction time and microwave radiation on the treatment process were investigated. The morphology, structure, and composition of the yielded nanostructures have been confirmed by X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), and scanning electron microscope (SEM). Also, the correlation between the reflectance, transmittance coefficient in the UV and the thickness of films was established. Furthermore, a two-point probe was used for resistivity measurements. We believe this simple chemical conversion technique can be further extended to the synthesis of other semiconductors with various morphologies.     

化学溶液法制备的Pb(Mg1/3Nb2/3)O3-PbTiO3薄膜的光学性能

用化学溶液方法在宝石衬底及有LaNiO₃缓冲层的Pt/TiO₂/SiO₂/Si衬底上制备了92%Pb(Mg_1/3Nb_2/3)O₃-8%PbTiO₃(PMNT)薄膜，X射线衍射测试结果表明：在有LaNiO₃缓冲层的Pt/TiO₂/SiO₂/Si衬底上制备的PMNT薄膜几乎是纯钙钛矿相，且薄膜 关键词： PMNT薄膜 光学性能 化学溶液法     

Investigation of chemical bath deposition of CdO thin films using three different complexing agents

Chemical bath deposition of CdO thin films using three different complexing agents, namely ammonia, ethanolamine, and methylamine is investigated. CdSO₄ is used as Cd precursor, while H₂O₂ is used as an oxidation agent. As-grown films are mainly cubic CdO₂, with some Cd(OH)₂ as well as CdO phases being detected. Annealing at 400 °C in air for 1 h transforms films into cubic CdO. The calculated optical band gap of as-grown films is in the range of 3.37-4.64 eV. Annealed films have a band gap of about 2.53 eV. Rutherford backscattering spectroscopy of as-grown films reveals cadmium to oxygen ratio of 1.00:1.74 ± 0.01 while much better stoichiometry is obtained after annealing, in accordance with the X-ray diffraction results. A carrier density as high as 1.89 × 10²⁰ cm⁻³ and a resistivity as low as 1.04 × 10⁻² Ω-cm are obtained.     

化学水浴法和磁控溅射法制备硫化镉薄膜的性能研究

以氯化铵、氯化镉、氢氧化钾和硫脲为反应物采用化学水浴法制备了硫化镉薄膜,为了作对比研究,采用射频磁控溅射以硫化镉为靶材,氩气为溅射气体,制备了硫化镉薄膜。采用X射线衍射、扫描电子显微镜和紫外-可见光光谱仪分别表征了硫化镉薄膜的结构、形貌和光学吸收特性。结果表明,采用以上两种方法制备的硫化镉均具有(002)择优取向,溅射法制备的硫化镉薄膜较致密,薄膜表面较光滑,平均晶粒尺寸在20～30nm;水浴法制备的硫化镉薄膜颗粒尺寸较小,缺陷较多。除了在短波段溅射所得硫化镉薄膜的透过率略差于水浴法所得硫化镉薄膜之外,溅射法制备的硫化镉薄膜的性能整体上优于水浴法制备的薄膜。两种方法制备的硫化镉薄膜的能隙在2.3～2.5eV。     

Deposition of copper iodide thin films by chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR) methods

In this paper, we report structural, morphological, electrical studies of copper iodide (CuI) thin films deposited onto glass substrates by chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR) methods. CuI thin films were characterized for their structural, morphological and wettability studies by means of X-ray diffraction (XRD), FT-Raman spectroscopy, scanning electron microscopy (SEM), optical absorption, and contact angle measurement methods. Thickness of thin films was 1 ± 0.1 μm measured by gravimetric weight difference method. The CuI thin films were nanocrystalline, with average crystal size of ～60 nm. The FT-IR study confirmed the formation of CuI on the substrate surface. SEM images revealed the compact and cube like structure for CuI thin films deposited by CBD and SILAR methods, respectively. Optical absorption study revealed optical energy gaps as 2.3 and 3.0 eV for CBD and SILAR methods, respectively. Wettability study indicated that CuI thin films deposited by SILAR method are more hydrophobic as compared to CBD method.     

Electrical and optical properties of Jäger-nickel (II)-based molecular-material thin films prepared by the vacuum thermal evaporation technique

Semiconductor molecular-material thin films of [6,13-Ac₂-5,14-Me₂-[14]-4,6,11,13-tetraenato-1,4,8,11-N₄] and the bidentate amines 1,4-diaminebutane, 1,12-diaminedodecane and 2,6-diamineanthraquinone have been prepared by vacuum thermal evaporation on corning glass substrates and crystalline silicon wafers. The films thus obtained were characterized by infrared (FTIR), ultraviolet-visible (UV-VIS) and photoluminescence (PL) spectroscopies. The surface morphology, thickness and structure of these films were analyzed by atomic force microscopy (AFM), ellipsometry and X-ray diffraction (XRD), respectively. IR spectroscopy showed that the molecular-material thin films exhibit the same intra-molecular bonds as the original compounds, which suggests that the thermal evaporation process does not significantly alter their bonds. The effect of temperature on conductivity was also measured in these samples; it was found that the temperature-dependent electric current is always higher for the voluminous amines with large molecular weights and suggests a semiconductor behavior with conductivities in the order of 10⁻⁶-10⁻¹ Ω⁻¹ cm⁻¹. Finally, the optical band gap (E_g) and cubic χ⁽³⁾ non-linear optical (NLO) properties of these amorphous molecular complexes were also evaluated from optical absorption and optical third harmonic generation (THG) measurements, respectively.     

Preparation of nanowall Bi2S3 films by chemical bath deposition

Nanowall shaped Bi₂S₃ films were prepared by chemical bath deposition in which ammonium citrate and thioacetamide were used as chelating reagent and sulfur source, respectively. The nanowall Bi₂S₃ films show large-surface-area nanowall shaped morphology. It is found that the pH value (pH = 6 or pH = 6.5) of the solution is a crucial parameter to obtain the nanowall shaped Bi₂S₃ films. The composition of the nanowall Bi₂S₃ films is close to the stoichiometric ratio of Bi₂S₃. The absorption edge of the nanowall shaped Bi₂S₃ films is located at around 900 nm, indicating that the optical bandgap of the Bi₂S₃ films is around 1.4 eV. The nanowall Bi₂S₃ films show obvious photo-sensitivity. The photo-to-dark conductivity ratios of the nanowall Bi₂S₃ films prepared at pH = 6 and pH = 6.5 are all around 50. This value is around five times than that of the non-nanowall shaped Bi₂S₃ films which is prepared at pH = 7.     

Atmospheric pressure chemical vapour deposition of vanadium diselenide thin films

Atmospheric pressure chemical vapour deposition (APCVD) of vanadium diselenide thin films on glass substrates was achieved by reaction of [V(NMe₂)₄] and ^tBu₂Se. X-ray diffraction showed that the VSe₂ films were crystalline with preferential growth either along the (1 0 1) or the (1 1 0) direction. Energy-dispersive analysis by X-rays (EDAX) gave a V:Se ratio close to 1:2 for all films. The films were matt black in appearance, were adhesive, passed the Scotch tape test but could be scratched with a steel scalpel. SEM showed that the films were composed of plate-like crystallites orientated parallel to the substrate which become longer and thicker with increasing deposition temperature. Attempts to produce vanadium selenide films were also performed using ^tBu₂Se and two different vanadium precursors: VCl₄ and VOCl₃. Both were found to be unsuitable for producing VSe₂ from the APCVD reaction with ^tBu₂Se. The VSe₂ showed charge density wave transition at 110-115 K.     

Mn doped ZnO nanostructured thin films prepared by ultrasonic spray pyrolysis method

Mn-doped ZnO thin films with different percentage of Mn content (0, 1, 3 and 5 at.%) and substrate temperature of 350 °C, were deposited by a simple ultrasonic spray pyrolysis method under atmospheric pressure. We have studied the structural and optical properties by using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and ultra-violet visible near infrared (UV–Vis-NIR) spectroscopy. The lattice parameters calculated for the Mn-doped ZnO from XRD pattern were found to be slightly larger than those of the undoped ZnO, which indicate substitution of Mn in ZnO lattice. Compared with the Raman spectra for ZnO pure films, the Mn-doping effect on the spectra is revealed by the presence of additional peak around 524 cm⁻¹ due to Mn incorporation. With increasing Mn doping the optical band gap increases indicating the Burstein–Moss effect.     

Fabrication and characterization of indium sulfide thin films deposited on SAMs modified substrates surfaces by chemical bath deposition

In an effort to explore the optoelectronic properties of nanostructured indium sulfide (In₂S₃) thin films for a wide range of applications, the In₂S₃ thin films were successfully deposited on the APTS layers (-NH₂-terminated) modified ITO glass substrates using the chemical bath deposition technique. The surface morphology, structure and composition of the resultant In₂S₃ thin films were characterized by FESEM, XRD, and XPS, respectively. Also, the correlations between the optical properties, photocurrent response and the thickness of thin films were established. According to the different deposition mechanisms on the varying SAMs terminational groups, the positive and negative micropatterned In₂S₃ thin films were successfully fabricated on modified Si substrates surface combining with the ultraviolet lithography process. This offers an attractive opportunity to fabricate patterned In₂S₃ thin films for controlling the spatial positioning of functional materials in microsystems.     

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.     

Consequence of oxidant to monomer ratio on optical and structural properties of Polypyrrole thin film deposited by oxidation polymerization technique

This paper reports the effect of oxidant to monomer (O/M) ratio on optical and structural properties of Polypyrrole (PPy) thin film deposited by chemical oxidation polymerization technique. Noticeable changes have observed in the properties of PPy thin films with O/M ratio. Cauliflower structure have been observed in FE-SEM images, wherein grain size is observed to decrease with increase in O/M ratio. AFM results are in good agreement with FE-SEM results. From FTIR spectra it is found that, PPy is in highly oxidized form at low O/M ratio but oxidation decreased with increase in O/M ratio. Also C–C stretching vibrations of PPy ring is decreased whereas C=C stretching is increased with ratio. Absorption peak around 450 nm corresponds to π–π^⁎ transition and around 800 nm for polarons and bipolarons. The intensity of such peaks confirms the conductivity of PPy, which is observed maximum at low O/M ratio and found to decrease with increase in ratio. Optical band gap (BG) is found to increase from 2.07 eV to 2.11 eV with increase in the O/M ratio.     

Preparation and properties of zinc blende and orthorhombic SnS films by chemical bath deposition

SnS (stannous sulfide) films were prepared by chemical bath deposition in which a novel chelating reagent ammonium citrate was used. The film has a zinc blende structure or an orthorhombic structure which is determined by the pH value and the temperature of the deposition solution. The reason for this result is considered to be that SnS films prepared under different conditions have different deposition mechanisms (ion-by-ion mechanism for the zinc blende structured SnS and hydroxide cluster mechanism for the orthorhombic structured SnS). The prepared SnS films are homogeneous and well adhered. SEM images show that the SnS films with different structures have different surface morphologies. Electrical test shows that the resistivity of the films is as low as 420 Ω cm and 3300 Ω cm for orthorhombic and zinc blende SnS films, respectively, which are much lower than the ever reported values. Persistent photoconductivity (PPC) phenomena are observed for both the films with zinc blende and orthorhombic structures by photo-current responses measurement. The optical bandgaps of the SnS films are determined to be 1.75 eV and 1.15 eV for zinc blende structure and orthorhombic structure, respectively.     

Effects of co-substitution on the electrical properties of BiFeO3 thin films prepared by chemical solution deposition

Ferroelectric BiFeO₃ thin films with Nd-Cr (or Sm-Cr) co-substitution (denoted by BNdFCr and BSmFCr, respectively) were deposited on the Pt(2 0 0)/TiO₂/SiO₂/Si(1 0 0) substrates by a chemical solution deposition method. X-ray diffraction patterns revealed the formation of BNdFCr and BSmFCr thin films without any secondary phases. The co-substituted BNdFCr (or BSmFCr) thin films, which were annealed at 550 °C for 30 min in N₂ atmosphere, exhibited enhanced electrical properties compared to BFO thin films with the remanent polarization (2P_r) and coercive electric field (2E_c) of 196, 188 μC/cm² and 600, 570 kV/cm with the electric field of 800 kV/cm, respectively. The leakage current densities of BNdFCr and BSmFCr thin films measured at room temperature were approximately three orders of magnitude lower than that of BFO thin film, and the leakage current at room temperature of the thin films exhibited three distinctive conduction behaviors. Furthermore, the values of pulse polarizations [i.e., +(P*-P^{^}) or −(P*-P^{^})] of BNdFCr and BSmFCr thin films were reasonably unchanged up to 1.4 × 10¹⁰ switching cycles.