Successive Ionic Layer Adsorption And Reaction Technique Research Articles

Effect of film thickness on the electrical and the photocatalytic properties of ZnO nanorods grown by SILAR technique

In this work, Zinc oxide (ZnO) thin films were synthesised by the successive ionic layer adsorption and reaction (SILAR) technique at various number of cycles (10–50 cycles). The effect of film thickness on the structural properties, surface morphology, optical and electrical properties, and sunlight assisted photocatalytic activities through photocatalytic degradation of Methylene Blue (MB) dye of ZnO thin films were studied. The energy dispersive x-rays (EDX) analysis confirmed the presence Zn and O elements. The x-rays diffraction (XRD) pattern showed the polycrystalline nature of ZnO thin films and the crystallite size increases with film thickness. The SEM images showed that a greater film thickness resulted in the growth of hexagonal nanorods arrays. Atomic force microscopy (AFM) images revealed that the surface roughness increases with film thickness yielding in an enhanced specific surface area. The UV—visible transmission spectra showed that increasing film thickness results in band gap expansion from 3.15 eV to 3.31 eV together with a reduction in optical transmittance. The estimated sheet resistance and resistivity were found to be in the range of 1.34–7.1 Ω sq−1 and 0.09–2.12 ×10–1 Ω.cm. The photocatalytic studies reveal that increasing film thickness leads to an improved photocatalytic efficiency of ZnO films. The enhanced photocatalytic activity of ZnO films is due to the increased surface area and low recombination rate of carriers charges (e−/h+), resulting from band gap expansion.

SILAR-Deposited CuO Nanostructured Films Doped with Zinc and Sodium for Improved CO2 Gas Detection.

Gas sensing is of significant importance in a wide range of disciplines, including industrial safety and environmental monitoring. In this work, a low-cost SILAR (Successive Ionic Layer Adsorption and Reaction) technique was employed to fabricate pure CuO, Zn-doped CuO, and Na-doped CuO nanotextured films to efficiently detect CO2 gas. The structures, morphologies, chemical composition, and optical properties of all films are characterized using different tools. All films exhibit a crystalline monoclinic phase (tenorite) structure. The average crystallite size of pure CuO was 83.5 nm, whereas the values for CuO/Zn and CuO/Na were 73.15 nm and 63.08 nm, respectively. Subsequently, the gas-sensing capabilities of these films were evaluated for the detection of CO2 in terms of sensor response, selectivity, recovery time, response time, and limits of detection and quantification. The CuO/Na film offered the most pronounced sensitivity towards CO2 gas, as evidenced by a sensor response of 12.8% at room temperature and a low limit of detection (LoD) of 2.36 SCCM. The response of this sensor increased to 64.5% as the operating temperature increased to 150 °C. This study thus revealed a brand-new CuO/Na nanostructured film as a highly effective and economically viable sensor for the detection of CO2.

Control of Manganese Oxide Hybrid Structure through Electrodeposition and SILAR Techniques for Supercapacitor Electrode Applications

Manganese oxide has been studied as a promising supercapacitor electrode due to its high theoretical capacitance, low cost, and environmental friendliness. Supercapacitor performance such as specific capacitance, resistance, and cycle life greatly depends on the morphology and crystal structure of manganese oxide. In this study, a Mn3O4 hybrid structure was successfully synthesized using electrodeposition and successive ionic layer adsorption and reaction (SILAR) techniques which are simple, cost-effective, and low-temperature wet chemical processes. It was found that Mn3O4 morphology is different depending on manganese precursors and synthesis techniques. Sea-grape-like and bird nest-like morphologies were obtained via the electrodeposition technique, while flower-like and nanoparticle morphologies were formed via the SILAR technique using manganese acetate and manganese sulfate as precursors, respectively. The hybrid structure of the nanoparticle-decorated bird nest-like heterostructure was prepared using manganese sulfate electrodeposition and subsequent SILAR deposition of manganese acetate. X-ray photoelectron spectroscopy confirmed the Mn3O4 formation. Electrochemical properties of manganese oxide hybrid structure were systematically studied with cyclic voltammetry and galvanostatic charge–discharge, showing the highest areal capacitance of 390 mF cm−2 at 0.1 mA cm−2 with series and charge transfer resistances down to 4.55 and 4.91 Ω in 1 M sodium sulfate electrolyte.

Growth-control of hexagonal CdS-decorated ZnO nanorod arrays with low-temperature preheating treatment for improved properties and efficient photoelectrochemical applications.

The limitations of oxide semiconductor-based solar cells in achieving high energy conversion efficiencies have prompted incessant research efforts towards the creation of efficient heterostructures. Despite its toxicity, no other semiconducting material can fully replace CdS as a versatile visible light-absorbing sensitizer. Herein, we explore the aptness of preheating treatment in the successive ionic layer adsorption and reaction (SILAR) deposition technique and improve the understanding of the principle and the effects of a controlled growth environment on thus-formed CdS thin films. Single hexagonal phases of nanostructured cadmium sulfide (CdS)-sensitized zinc oxide nanorods arrays (ZnO NRs) have been developed without the support of any complexing agent. The influences of film thickness, cationic solution pH and post-thermal treatment temperature on the characteristics of binary photoelectrodes have been investigated experimentally. Interestingly, the preheating-assisted deposition of CdS, which is rarely applied for the SILAR technique, resulted in improved photoelectrochemical performance similar to the post-annealing effect. The X-ray diffraction pattern revealed that optimized ZnO/CdS thin films were polycrystalline with high crystallinity. Examination of the morphology of the fabricated films via field emission scanning electron microscopy showed that film thickness and medium pH altered the growth mechanism of nanoparticles, thereby changing their particle sizes, which had a significant influence on the film's optical behavior. The effectiveness of CdS as a photosensitizer and the band edge alignment for ZnO/CdS heterostructures were evaluated using ultra-violet visible spectroscopy. Facile electron transfer in the binary system as evidenced in electrochemical impedance spectroscopy Nyquist plots, therefore, promotes higher photoelectrochemical efficiencies from 0.40% to 4.30% under visible light illumination as compared with the pristine ZnO NRs photoanode.

Chlorophyll-a functionalised Zn-Cd-S thin film fabricated by SILAR technique for dye sensitised solar cells

Photoelectrochemical performance of DSSCs based on natural extracted chlorophyll-a dye sensitised Zn-Cd-S thin film semiconductor electrodes on Cr-plated stainless steel substrates as photoanodes are studied. Thin film electrode materials prepared by successive ionic layer adsorption and reaction (SILAR) method are characterised by using Powder X-ray diffraction (PXRD) spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) and UV–VIS spectroscopy. The prepared Zn-Cd-S thin films are found to be nanocrystalline with a crystal size of ≈ 6.6 nm. The optical band gap energy of the thin films found is to be ≈ 2.9 eV. Chlorophyll-a dye used as sensitizer for DSSC, is extracted from Marigold leaves using acetone as solvent. The optical to electrical energy conversion efficiency of the DSSC using 6 h chlorophyll-a dye loaded Zn-Cd-S thin film is estimated to be 0.988% with fill factor of 52%.

Rational Design of Photoelectrodes for the Fully Integrated Polymer Electrode Membrane–Photoelectrochemical Water-Splitting System: A Case Study of Bismuth Vanadate

Photoelectrochemical (PEC) reactors based on polymer electrolyte membrane (PEM) electrolyzers are an attractive alternative to improve scalability compared to conventional monolithic devices. To introduce narrow band gap photoabsorbers such as BiVO4 in PEM-PEC system requires cost-effective and scalable deposition techniques beyond those previously demonstrated on monolithic FTO-coated glass substrates, followed by the preparation of membrane electrode assemblies. Herein, we address the significant challenges in coating narrow band gap metal-oxides on porous substrates as suitable photoelectrodes for the PEM-PEC configuration. In particular, we demonstrate the deposition and integration of W-doped BiVO4 on porous conductive substrates by a simple, cost-effective, and scalable deposition based on the SILAR (successive ionic layer adsorption and reaction) technique. The resultant W-doped BiVO4 photoanode exhibits a photocurrent density of 2.1 mA·cm–2, @1.23V vs RHE, the highest reported so far for the BiVO4 on any porous substrates. Furthermore, we integrated the BiVO4 on the PEM-PEC reactor to demonstrate the solar hydrogen production from ambient air with humidity as the only water source, retaining 1.55 mA·cm–2, @1.23V vs RHE. The concept provides insights into the features necessary for the successful development of materials suitable for the PEM-PEC tandem configuration reactors and the gas-phase operation of the reactor, which is a promising approach for low-cost, large-scale solar hydrogen production.

Photo-characterization of Organic Dye-Sensitized Tin Oxide Films

Objectives: To develop organic dye sensitized film electrodes from highly porous tin oxide (SnO2) thin films prepared at room temperature using the SILAR technique. Methods/Analysis: SnO2 films were fabricated by the successive ionic layer adsorption and reaction (SILAR) technique at room temperature and its sensitization was done using the organic dye Rose Bengal (RB). The effect of sensitization on the as-grown and annealed film electrodes was investigated. Findings : Crystalline films with cauliflower-like morphology exhibit a large inherent adsorptive surface area and exhibit steady transmittance of 60-80% in the visible region. As-grown SnO2 films possess higher porosity and lower refractive index than that of the annealed films. SnO2 films have a resistivity in the range of 10-2-10-3 ΩcmΩcm. The dye adsorbed SnO2 film electrodes have much higher absorbance and cover a broad visible region compared to the bare SnO2 film electrodes. RB sensitization leads to an accelerated improvement in absorbed photon energy through the visible region of the spectrum extending from 2 to 3.75 eV. Novelty: Contrary to the sophisticated methods of preparation in the reported literature, highly porous crystalline SnO2 thin films were prepared at room temperature, using glacial acetic acid and hydrogen peroxide by a cost-effective simple wet chemical method. Work demonstrates that SnO2 films sensitized with RB act as an excellent dye-sensitized electrode, which can absorb almost half the visible spectrum (400-600 nm) of solar radiations. We believe that this is the unique report of surface modification of wet chemically prepared SnO2 electrodes by the photo-sensitizer RB. Keywords Photo­characterization, rose bengal, sensitization, thin films, tin oxide electrodes

Construction of columnar cactus-like 2D/1D CdxCu1-xS@CuO shell-core structure photocatalyst for the reduction of CO2 to methanol

Nanostructure photocatalysts with unique and stable structure and high specific surface area are expected to be widely used in photocatalytic CO 2 reduction. In this paper, columnar cactus-like Cd x Cu 1-x S/CuO/CM composite catalyst was prepared by a simple method combining thermal oxidation with a successive ionic layer adsorption and reaction (SILAR) technique. The combination of Cd x Cu 1-x S nanosheets and CuO nanowires can significantly improve the specific surface area, capacity of light capture and absorption and separation of electrons and holes inside which were beneficial for efficiency of photocatalysis. Their complementary conduction band and valence band positions synergistically form p-n heterojunctions, achieving the effect of multi-level charge separation. The 2D/1D Cd x Cu 1-x S/CuO/CM have better photocatalytic activity than pure CuO nanowires in the production of methanol by using solar energy to reduce CO 2 . After 4 h of irradiation, the methanol yield of 2D/1D Cd x Cu 1-x S/CuO/CM reached 3.60 μmol g −1 cat, which was 2.81 times the yield of pure CuO/CM. This work has certain significance for the development of new energy and environmental protection. • The columnar cactus-like Cd x Cu 1-x S/CuO/CM was prepared by the thermal oxidation and SILAR technique. • The catalyst had regular morphology, more active sites, favorable visible light absorption capacity and stability. • The gas - liquid - solid three - phase reactor was used. • The yield of methanol was 3.60 μmol g −1 cat after 4 h irradiation.

Compact continuous BiOI film for solid-state solar cell via faster lifting speed of the dip-SILAR technique at room temperature

This research paper reports for the first time room temperature deposited, and 100 °C annealed, successive ionic layer adsorption and reaction (SILAR) prepared bismuth oxyiodide (BiOI) continuous film to produce a stable solid-state solar cell. After the successful deposition of continuous BiOI film on the TiO2 electron transport layer (ETL), the hole transport layer (HTL) colloidal graphite has been introduced. Our investigation confirms the continuous growth of the BiOI film at faster lifting speed (e.g., 30 mm/s) of the SILAR technique, while separated flaky structure was observed at slower lifting speed (e.g., 4 mm/s). The BiOI material structure converted into a continuous flower shape at a faster lifting speed, preventing the HTL layer penetration and short circuit with ETL. After ensuring the continuous film, we have observed the short-circuit current density (JSC = 4.7 mA/cm2), open-circuit voltage (VOC = 0.35 V), and power conversion efficiency (η = 0.39%) of the cell at 30 cycles condition. This synthesis technique will encourage the research world to think more interestingly about environmentally friendly BiOI solid-state solar cells.

Non-linear optical study of hierarchical 3D Al doped ZnO nanosheet arrays deposited by successive ionic adsorption and reaction method

Successive ionic layer adsorption and reaction (SILAR) method is based on the adsorption and reaction of the ions in the cationic solution and the ionic solution, respectively. This method is simple, inexpensive, large-scale deposition, effective way for deposition on 3D substrates, low-temperature process and represents an easy way for the preparation of doped, composite and heterojunction materials. To take advantage of this method and the ZnO nanostructures, various parameters have been optimized.Undoped and Aluminum (Al) doped ZnO nanostructures were prepared by the SILAR technique. The characterization of the nanostructures prepared was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoemission spectroscopy (XPS), UV–Vis spectrometry and nonlinear optical analysis (NLO). The structural, compositional and optical properties confirm the introduction of Al3+ ions into the ZnO matrix. As a result, an enhancement of the crystallinity, enhancement of the light absorption and a change in the morphology of the nanostructures were observed.The laser stimulated nonlinear optical effects of the second and third harmonic generation were done using a fundamental laser beam. The laser stimulated NLO values obtained are at least 10% higher than the doped ZnO nanomaterials synthesized by other methods using the same set-up.

Effect of Coating and Annealing on Giant Magneto Impedance in Co and Fe-Based Amorphous Wires

Effect of coating with different chemical complexes on giant magneto impedance effect (GMI) was experimentally investigated in Fe and Co-based amorphous wires. The successive ionic layer adsorption and reaction (SILAR) technique was used for coating of the samples at room temperature. The SILAR method mainly based on adsorption and reaction on the ions from the solution and rinsing. Co and Fe-based amorphous wires were coated with CoO, asphaltene and ZnO chemical complexes. The coating thickness was determined to be about 1 μm thick. Maximum GMI ratio for Co and Fe-based samples were measured at 4 MHz and 5 MHz frequency, respectively. Influence of annealing at different temperatures on GMI effect was also experimentally investigated in the same samples. The coated samples were annealed at 300 C, 400 C, 500 C and 600 C temperatures in order to stress relief for 30 minutes. It is observed that the GMI ratio on Co- and Fe-based ZnO coated samples was highest at 500 ºC, while it was maximum on CoO coated Co-based samples at 400 ºC and on CoO coated Fe-based samples at 500 ºC. The highest GMI ratio among the measured samples was detected as 216 on the Fe-based, ZnO coated and annealed sample at 500 ºC at 5 MHz, while the smallest GMI ratio, was found to be as 88 on Co-based as-cast sample at 4 MHz. The measurements show that the GMI ratio is a combined effect of coating, annealing and frequency of ac current in a static magnetic field. Keywords Amorphous magnetic materials, SILAR technique, giant magneto impedance. Special Issue of Educational Sciences DOI: 10.7176/JSTR/6-06-03

Complexing agent triethanolamine mediated synthesis of nanocrystalline CuO thin films at room temperature via SILAR technique

In the present work, nanostructured cupric oxide (CuO) thin films have been successfully deposited on glass substrates by successive ionic layer adsorption and reaction (SILAR) technique at room temperature. The influence of complexing agent as triethanolamine (TEA) on the structural, morphological, optical and electrical characteristics of nanocrystalline CuO thin films have been examined in detail. Structural studies confirm that all the films were polycrystalline nature having a monoclinic crystalline form and displayed (1¯11) and (111) preferential orientations. The estimated crystallite values ranged from 17.47 to 19.95 nm. The surface morphology of CuO thin films was examined through scanning electron microscopy and materials microscope studies. Surface studies revealed that homogeneously distributed CuO nanostructures on the film surfaces. The optical studies showed that band gap energy values of the CuO thin films were increased from 1.33 to 2.00 eV as a function of increasing TEA concentration. Meanwhile, the average transmittance of all the films had increased from 2.5 to 42.5% with the increasing TEA concentration. FTIR studies identified the formation of single phase CuO and chemical bonding of the complexing agent. The resistivity value of CuO thin film synthesized without TEA was 3.74 × 105 Ω cm and the resistivity consequently increased to 509 × 105 Ω cm with TEA concentration of 1.0 M%. A high figure of merit (786 × 10−12 Ω−1) was obtained for complexing agent concentration of 0.25 M%.

Effects of proton irradiation on structures and photo-catalytic property of nano-TiO2/CNTs films

Thin nano-TiO2 films were prepared using aqueous SILAR (successive ionic layer adsorption and reaction) technique on the carbon nanotubes (CNTs) films using titanium trichloride and water as precursors. TiO2-deposited carbon nanotubes (TiO2/CNTs) films were irradiated with 120 keV proton beam, and then analyzed using Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and photocatalytic degradation tests. The results indicate that irradiation could transfer the amorphous deposited TiO2 films to a crystalline state, while the CNTs substrate would also be damaged, namely CNT tube diameter shrinkage and the Raman peak ratio of ID/IG decreases with increasing proton fluences. It was also found that the TiO2 modification could result in more damage to the CNTs substrate as the proton fluence is lower. This is largely due to the fact that the process of activation before deposition could cause damage to the CNTs to some degree. It is interested to be noted that proton irradiation would induce the nano-TiO2/CNTs films to show the remarkable photocatalytic degradation behaviors using methylene blue as the test additive. Moreover, the case with thinner TiO2 on CNTs appears relatively better photocatalytic degradation behaviors. The reasons for the change of photocatalytic behaviors may be due to both crystallization of TiO2 layers and carrier trapping effect of CNTs.

Effect of the number of cycles on the optical and structural properties of Mn3O4 nanostructures obtained by SILAR technique

In this study, nanostructured Mn3O4 (manganese oxide) thin films were successfully obtained by successive ionic layer adsorption and reaction (SILAR) method on the soda lime glass substrates using Manganese Nitrate (Mn(NO3)2) and Ammonium hydroxide (NH4(OH)) as cationic and anionic precursors respectively. Structural and morphological characterizations of the Mn3O4 films obtained at different cycles were determined using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The crystal structure of the thin films were also confirmed by RAMAN spectroscopy. Optical properties such as absorption, transmission, reflection, extinction coefficient and optical band gap of nanostructured Mn3O4 thin films were determined by UV–Vis spectroscopy. SEM images showed that the manganese oxide nanosheets formed uniformly on substrate surface. As the deposition cycles increased, nano-sheets structure deteriorated. The optical band gap of Mn3O4 thin films varied from 2.12 to 2.59 eV, depending on the increase in number of cycles. From contact angle measurements of thin films, it was determined that thin films had hydrophilic character.

SILAR controlled CdSe nanoparticles sensitized ZnO nanorods photoanode for solar cell application: Electrolyte effect

Controlled growth of different sizes of cadmium selenide (CdSe) nanoparticles over well aligned ZnO nanorods have been performed using successive ionic layer adsorption and reaction (SILAR) technique at room temperature (27 °C) in order to form nano heterostructure solar cells. Deposition of compact layer of zinc oxide (ZnO) by SILAR technique on fluorine doped tin oxide (FTO) coated glass substrate followed by growth of vertically aligned ZnO nanorods array using chemical bath deposition (CBD) at low temperature (<100 °C). Different characterization techniques viz. X‐ray diffractometer, UV–Vis spectrophotometer, field emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy have been used to know the structural, optical, morphological and compositional properties of synthesized nano heterostructure. The photovoltaic performance of the cells with variation in SILAR cycles for CdSe and with use of different electrolytes have been recorded as J-V characteristics and the maximum conversion efficiency of 0.63% have been attained with ferro/ferri cyanide electrolyte for 12 cycles CdSe coating over 1-D ZnO nanorods.

Addressing the issue of under-utilization of precursor material in SILAR process: Simultaneous preparation of CdS in two different forms – Thin film and powder

To overcome the major limitation of the successive ionic layer adsorption and reaction (SILAR) technique – the under-utilization of the precursor material – in the present work, simultaneous fabrication of CdS thin films and CdS powder is attempted.CdS films were prepared by employing SILAR technique using cadmium acetate dihydrate and thiourea as cationic and anionic precursor materials for Cd and S, respectively. The precipitated powder materials in the cationic and anionic baths which are usually discarded as wastage are collected and processed to obtain CdS powders. In another trial, the cationic and anionic bath solutions are mixed and the resultant precipitate is collected for characterization. The obtained CdS in thin film and powder forms are analyzed for structural, surface morphological, optical, compositional and photocatalytic properties. The results clearly showed that the obtained CdS films are good candidates for considering them for solar cell applications. Similarly, CdS powders obtained from the mixture of cationic and anionic bath solutions are found to have good photocatalytic efficacy. Thus the demerits of under-utilization of precursor materials in SILAR process for the deposition of CdS films is overcome to certain extent as 63% of the wastage is recovered as useful product.

Synthesis of MgO thin films grown by SILAR technique

Different thickness MgO thin films were grown on the glass substrate by successive ionic layer adsorption and reaction (SILAR) method as the first study in literature. X-ray diffraction (XRD) measurements demonstrate the cubic MgO structures and samples have (002), and (220) peaks. All film has nanoball structures observed from the scanning electron microscope (SEM) images. The band gap and transmittance values of MgO thin films decrease with increasing thickness. The photoluminescence (PL) spectrum demonstrates that samples have three visible emissions changing with thickness at 381 nm violet emission, 457 nm blue emission and 535 nm green emission. X-ray photoelectron spectroscopy (XPS) spectrum present confirms the elemental signals from carbon (C), oxygen (O) and magnesium (Mg) atoms in the sample. Both Moss and Herve and Vandamme relations refractive index values n, ε0, and ε∞ values and amount of oxygen increase with raising thickness of MgO thin films.

Chemical synthesis and characterization of CdSe thin films deposited by SILAR technique for optoelectronic applications

Abstract CdSe thin films were deposited on the glass substrate by successive ionic layer adsorption and reaction (SILAR) method. Different sets of the film are prepared by changing the number of immersion cycles as 30, 40, 50 and 60. Further the effect of a number of immersion cycles on the characteristic structural, morphological, optical and electrical properties of the films are studied. The XRD studies revealed that the deposited films showed hexagonal structure with most prominent reflection along (1 0 1) plane. Moreover, the peak intensity of (1 0 1) plane is found to be increased as the number of immersion cycles is increased. All the thin films look relatively smooth and homogeneous covering the entire surface area in FESEM image. Optical properties of the CdSe thin films for a different number of immersion cycles were studied, which indicates that the absorbance increases with the increase in the immersion cycles. Furthermore, the optical band-gap in conjunction with the electrical resistivity was found to get decreased with increase in the immersion cycles. A good correlation between the number of immersion cycles and the physical properties indicates a simple method to manipulate the CdSe material properties for optoelectronic applications.

Employing ZnS as a capping material for PbS quantum dots and bulk heterojunction solar cells

Formation of bulk heterojunctions by incorporating colloidal quantum dots into a mesoporous substrate is anticipated to yield efficient charge collection and complete light absorption. However, it is still challenging in view of the bulky nature of the colloidal quantum dots and the ex situ deposition route. In this study, the feasibility of employing ZnS as a capping material for PbS quantum dots is dissected by carefully designed control experiments, with reference to the formation of bulk heterojunctions by successive ionic layer adsorption and reaction (SILAR) at ambient conditions. The results reveal that the underlying ZnS layer facilitates the PbS deposition by an ion exchange process, while the overlaying ZnS layer tends to cover the PbS in a manner similar to a physical stacking process. Therefore, PbS quantum dots capped with amorphous ZnS are developed with the SILAR technique, which could be used to fill up the mesoporous substrates and thus construct bulk heterojunctions. The hole collection is the limiting factor of such bulk heterojunction solar cells, as demonstrated by inserting a conductive polymer layer in the control devices. Further development of the quantum dot system is discussed in consideration of the fundamental issues presented in this study.

Rectification of sulphur deficiency defect in CdS based films by introducing a novel modification in the SILAR cyclic process

In the present study, a novel modification is introduced in the dipping process of the SILAR (successive ionic layer adsorption and reaction) technique which is one of the important chemical solution techniques, generally used for the deposition of cadmium sulphide films. This study clearly establishes that this improved SILAR (ISILAR) technique enables one to rectify the sulphur deficiency, generally present in CdS films and there by obtain a near stoichiometric undoped and doped CdS thin films. In the present work, Fe doped CdS thin films are also deposited on glass substrates using this ISILAR technique. In this ISILAR technique, during the automated dipping process, a fresh anionic solution bath replaces the used one when the supply of S2− ions from this anionic solution declines to an optimized threshold value. As a result of this modification, the stoichiometric deviation drastically reduces from 12.9% to 3.3% for CdS films and from 20.2% to 0.6% for CdS:Fe films. The underlying mechanism for this observed improvement in the stoichiometry is elaborated in this article. The CdS films deposited using this ISILAR technique exhibit better transmittance values compared to several reported values. The XRD studies reveal that the deposited films have good crystalline quality. The magnetic studies show that at higher Fe doping (15 at.%) level, a ferromagnetic nature is observed in the lower applied magnetic field region. The optical band gap decreases gradually with the increase in the Fe doping level and this result is found to be supported by photoluminescence results.