C.D. Lokhande

Chemical deposition method for metal chalcogenide thin films

Abstract Metal chalcogenide thin films preparation by chemical methods are currently attracting considerable attention as it is relatively inexpensive, simple and convenient for large area deposition. A variety of substrates such as insulators, semiconductors or metals can be used since these are low temperature processes which avoid oxidation and corrosion of substrate. These are slow processes which facilitates better orientation of crystallites with improved grain structure. Depending upon deposition conditions, film growth can take place by ion-by-ion condensation of the materials on the substrates or by adsorption of colloidal particles from the solution on the substrate. Using these methods, thin films of group II–VI, V–VI, III–VI etc. have been deposited. Solar selective coatings, solar control, photoconductors, solid state and photoelectrochemical solar cells, optical imaging, hologram recording, optical mass memories etc. are some of the applications of metal chalcogenide films. In the present review article, we have described in detail, chemical bath deposition method of metal chalcogenide thin films, it is capable of yielding good quality thin films. Their preparative parameters, structural, optical, electrical properties etc. are described. Theoretical background necessary for the chemical deposition of thin films is also discussed.

Deposition of metal chalcogenide thin films by successive ionic layer adsorption and reaction (SILAR) method

During last three decades, successive ionic layer adsorption and reaction (SILAR) method, has emerged as one of the solution methods to deposit a variety of compound materials in thin film form. The SILAR method is inexpensive, simple and convenient for large area deposition. A variety of substrates such as insulators, semiconductors, metals and temperature sensitive substrates (like polyester) can be used since the deposition is carried out at or near to room temperature. As a low temperature process, it also avoids oxidation and corrosion of the substrate. The prime requisite for obtaining good quality thin film is the optimization of preparative provisos viz. concentration of the precursors, nature of complexing agent, pH of the precursor solutions and adsorption, reaction and rinsing time durations etc.In the present review article, we have described in detail, successive ionic layer adsorption and reaction (SILAR) method of metal chalcogenide thin films. An extensive survey of thin film materials prepared during past years is made to demonstrate the versatility of SILAR method. Their preparative parameters and structural, optical, electrical properties etc are described. Theoretical background necessary for the SILAR method is also discussed.

Porous polypyrrole clusters prepared by electropolymerization for a high performance supercapacitor

Different nanostructures (Ns), such as nanobelts, nanobricks and nanosheets, of polypyrrole (PPy) were successfully fabricated on stainless steel substrates by simply varying the scan rate of deposition in the potentiodynamic mode. These PPy Ns were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and surface area measurement. The XRD analysis showed the formation of amorphous PPy thin films, and the FTIR studies confirmed characteristic chemical bonding in the PPy materials. SEM images depicted that a high scan rate of deposition can form multilayer nanosheets with high porosity leading to a system with excellent processability. The PPy nanosheets possess a higher Brunauer-Emmett-Teller (BET) surface area of 37.1 m 2 g -1 than PPy nanobelts and nanobricks. The supercapacitive performances of different PPy Ns were evaluated using cyclic voltammetry (CV) and galvanostatic charge-discharge techniques in 0.5 M H 2SO 4. A maximum specific capacitance of 586 F g -1 was obtained for multilayer nanosheets at a scan rate of 2 mV s -1. In addition, impedance measurements of the different Ns of PPy electrodes were performed suggesting that the PPy electrodes with multilayer nanosheets are promising materials for the next generation high performance electrochemical supercapacitors.

Chemical bath deposition of indium sulphide thin films : preparation and characterization

Abstract Indium sulphide (In2S3) thin films have been successfully deposited on different substrates under varying deposition conditions using chemical bath deposition technique. The deposition mechanism of In2S3 thin films from thioacetamide deposition bath has been proposed. Films have been characterized with respect to their crystalline structure, composition, optical and electrical properties by means of X-ray diffraction, TEM, EDAX, optical absorption, TRMC (time resolved microwave conductivity) and RBS. Films on glass substrates were amorphous and on FTO (flourine doped tin oxide coated) glass substrates were polycrystalline (∈ phase). The optical band gap of In2S3 thin film was estimated to be 2.75 eV. The as-deposited films were photoactive as evidenced by TRMC studies. The presence of oxygen in the film was detected by RBS analysis.

Structural and optical properties of electrodeposited Bi2S3, Sb2S3 and As2S3 thin films

Abstract Thin films of Bi2S3, Sb2S3 and As2S3 have been prepared by the electrodeposition technique from aqueous acidic baths using Na2S22O3 as a sulphide source. The films deposited from an EDTA-complexed bath are thin, uniform and adherent to the substrate. The electrodeposition potentials were estimated by polarization curves. The structural and optical properties of the films have been studied. The X-ray diffraction pattern of the films shows that they are polycrystalline. The estimated optical bandgap energies for Bi2S3, Sb2S3 and As2S3 are 1.58 eV, 1.74 eV and 2.35 eV respectively.

Preparation and characterization of spray pyrolysed cobalt oxide thin films

Abstract Cobalt oxide thin films were prepared by the spray pyrolysis method on amorphous glass substrates kept at 300 °C. The films formed were uniform, pin-hole free, and strongly adherent to the substrates. The X-ray diffraction studies revealed that the films consist of Co 3 O 4 oxide phase. The optical and the electrical properties of the film were also studied.

Chemical deposition of metal chalcogenide thin films

Abstract Metal chalcogenide thin film preparation by chemical deposition is currently attracting considerable attention as it is relatively inexpensive, simple and convenient for large area deposition. A variety of substrates such as insulators, semiconductors or metals can be used since it is a low temperature process which avoids oxidation or corrosion of metallic substrates. It is a slow process which facilitates better orientation of crystallites with improved grain structure. Depending upon the deposition conditions, film growth can take place by ion-by-ion condensation of the materials on the substrates or by adsorption of the colloidal particles from the solution onto a substrate. Using this method thin films of groups II–VI, IV–VI, V–VI, I–III–VI etc. have been deposited. In this review article, the theoretical background of chemical deposition is described in detail. A survey of binary and ternary metal chalcogenide thin films is given with respect to their preparative parameters, structural, optical and electrical properties. Such films have been used in solar selective coatings, solar control photoconductors, solid state and photoelectrochemical solar cells.

Achievement of 4.51% conversion efficiency using ZnO recombination barrier layer in TiO2 based dye-sensitized solar cells

The authors report the use of chemically deposited ZnO recombination barrier layer for improved efficiency of TiO2 based dye-sensitized solar cells. The ZnO layers of different thicknesses were deposited on spin coated porous TiO2. The presence of ZnO over TiO2 was confirmed by x-ray diffraction, electron dispersive x-ray analysis, and supported by x-ray photoelectron spectroscopy, proved inherent energy barrier between the porous TiO2 electrode and lithium iodide electrolyte. They found that TiO2 based dye-sensitized solar cell with 30nm ZnO layer thickness showed 4.51% efficiency due to the formation of efficient recombination barrier at electrode/electrolyte interface. Further increase in ZnO barrier thickness may leak the electrons injected from the dye due to its low electron effective mass of 0.2me.

Temperature influence on morphological progress of Ni(OH)2 thin films and its subsequent effect on electrochemical supercapacitive properties

The temperature dependent morphological evolution and its effect on the electrochemical supercapacitive properties of Ni(OH)2 thin films have been systematically investigated. A temperature dependent growth mechanism model is proposed for the changes in microstructure. Different nanostructures of Ni(OH)2 thin films such as nanoplates, stacked nanoplates, nanobelts and nanoribbons have been fabricated by varying the deposition temperature. An X-ray diffraction study discloses the orientations of different nanostructures and the formation of nanocrystalline β-Ni(OH)2. Further, these Ni(OH)2 nanostructures demonstrate excellent surface properties like uniform surface morphology, good surface area, pore volume and uniform pore size distribution. The electrochemical supercapacitive properties of Ni(OH)2 nanostructures have been investigated by cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy techniques. The electrochemical studies of the Ni(OH)2 samples show an obvious influence of surface properties on the pseudocapacitance. The maximum specific capacitance of 357 F g−1 was evaluated for nanoplates at a scan rate of 5 mV s−1. Furthermore, all these Ni(OH)2 samples show good long-term cycling performances in KOH electrolyte. The Ragone plots ascertain good power and energy densities of all Ni(OH)2 nanostructured samples. Subsequently, electrochemical impedance measurements for the different nanostructures of Ni(OH)2 electrodes are assessed indicating that the Ni(OH)2 nanoplates structured electrodes are suitable for good capacity electrochemical supercapacitors.

Process and characterisation of chemical bath deposited manganese sulphide (MnS) thin films

Manganese sulphide (MnS) thin films have been deposited by a simple and inexpensive chemical bath deposition (CBD) method using thioacetamide as a sulphide ion source from an aqueous medium. The effect of preparative parameters on the film growth and quality has been studied. The MnS films have been characterised by XRD, TEM, SEM, EDAX, RBS, optical absorption and (time resolved microwave conductivity) TRMC techniques for their structural, compositional, and optical properties. The as-deposited MnS film on glass substrate consists of nanocrystalline grains. The film consists of mixed (cubic and hexagonal) phases. The optical band gap of the film is estimated to be 3.02 eV.