S. Shaji

Chemically deposited Sb2S3 thin films for optical recording

Laser induced changes in the properties of Sb2S3 thin films prepared by chemical bath deposition are described in this paper. Sb2S3 thin films of thickness 550 nm were deposited from a solution containing SbCl3 and Na2S2O3 at 27 °C for 5 h. These thin films were irradiated by a 532 nm continuous wave laser beam under different conditions at ambient atmosphere. X-ray diffraction analysis showed amorphous to polycrystalline transformation due to laser exposure of these thin films. Morphology and composition of these films were described. Optical properties of these films before and after laser irradiation were analysed. The optical band gap of the material was decreased due to laser induced crystallization. The results obtained confirm that there is further scope for developing this material as an optical recording media.

Progress in development of copper antimony sulfide thin films as an alternative material for solar energy harvesting

The increasing energy demand and the limitations of the existing technologies due to the scarcity, cost and toxicity of the materials urge the researchers to hunt for efficient thin film solar cells based on earth-abundant, inexpensive and less toxic materials. For a decade, binary and ternary antimony based sulfides have gained attention due to their possible applications in solar cells. This interest is the basis of this review. In this review article, we describe basic properties of copper antimony sulfide (CuSbS2) thin films to investigate their photovoltaic applications. A detailed description of the preparation methods, studies on morphologies and optoelectronic properties based on published work, including our experience are presented. A systematic review is done to demonstrate emerging interest in the photovoltaic performance of this compound. This review gives an in depth discussion on the structure, morphology, optical and electrical properties of copper antimony sulfide thin films.

Synthesis and Properties of Platinum Nanoparticles by Pulsed Laser Ablation in Liquid

Platinum Pt nanoparticles were synthesized by pulsed laser ablation in liquid PLAL technique in different liquids acetone, ethanol, and methanol. Ablation was performed using a Q-switched Nd:YAG laser with output energy of 230 mJ/pulse for 532 nm wavelength. Ablation time and laser energy fluence were varied for all the liquids. Effects of laser energy fluence, ablation time, and nature of the liquid were reported. The mean size, size distributions, shape, elemental composition, and optical properties of Pt nanoparticles synthesized by PLAL were examined by transmission electron microscopy TEM, X-ray photoelectron spectroscopy XPS, and UV-Visible absorption spectroscopy.

Effects of Liquid Medium and Ablation Wavelength on the Properties of Cadmium Sulfide Nanoparticles Formed by Pulsed-Laser Ablation

Pulsed-laser ablation in liquid (PLAL) is a green synthesis technique to obtain semiconductor nanomaterials in colloidal form. Herein, cadmium sulfide (CdS) nanoparticles were synthesized by the pulsed-laser ablation of a CdS target in different liquid media by using λ=532 and 1064 nm outputs from a pulsed (10 ns, 10 Hz) Nd:YAG laser at different ablation fluence values. The morphology, structure, crystalline phase, elemental composition, optical, and luminescent properties of CdS nanomaterials were analyzed by using transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV/Vis absorption spectroscopy, and fluorescence spectroscopy. By changing the liquid medium and ablation wavelength, CdS nanoparticles with different morphology and size were formed, as demonstrated by using TEM analysis. The crystallinity and chemical states of the ablation products were confirmed by using XRD and XPS analyses. The optical bandgap of the CdS nanoparticles was dependent on the ablation wavelength and the fluence. These nanocolloids presented different green emissions, which implied the presence of several emission centers. CdS nanocolloids in distilled water catalyzed the photocatalytic decay of methylene blue dye under light irradiation from a solar simulator.

Synthesis and Properties of Tin Sulfide Thin Films from Nanocolloids Prepared by Pulsed Laser Ablation in Liquid

Tin sulfide (SnS) nanoparticles were synthesized by pulsed laser ablation in liquid (PLAL) technique using an Nd:YAG laser operated at 532 nm. SnS thin films were deposited by spraying the colloidal suspension onto the heated substrates. The influence of different liquid media (dimethyl formamide and isopropyl alcohol) on the thin film properties were studied. Morphology, crystalline structure, and chemical composition of the nanoparticles were identified using transmission electron microscopy with energy dispersive X-ray analysis. The crystalline structure of the thin films was analyzed by using grazing incidence X-ray diffraction, and the chemical states by X-ray photoelectron spectroscopy. Scanning electron microscopy was employed for the morphological analysis of the thin films. Annealing the films at 380 °C improved the crystallinity of the films exhibiting a layered morphology, which may be useful in optoelectronic and sensing applications. Cyclic voltammetry studies showed that the films have good electrochemical properties.

STRUCTURAL PROPERTIES OF AlN FILMS WITH OXYGEN CONTENT DEPOSITED BY REACTIVE MAGNETRON SPUTTERING: XRD AND XPS CHARACTERIZATION

A set of aluminium nitride (AlN) and oxidized AlN (AlNO) thin films were grown with the technique of direct current (dc) reactive magnetron sputtering. The main purpose of this investigation is to explore the influence of the oxygen on the structural properties of AlN and AlNO films. The crystalline properties and chemical identification of phases were studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. Electrical properties were analyzed from I-V measurements. It was found that films crystallized under the AlN wurzite structure and presented a polycrystalline preferential growth along [0001] direction, perpendicular to substrate. Small amounts of secondary aluminium oxide phases were detected too. The oxide phases can induce defects, which can alter crystallinity of films.

Chemically Deposited Silver Antimony Selenide Thin Films for Photovoltaic Applications

Silver antimony selenide (AgSbSe 2 ) thin films were prepared by heating sequentially deposited antimony sulphide (Sb 2 S 3 ), silver selenide (Ag 2 Se) and Ag thin films in close contact with a selenium thin film. Sb 2 S 3 thin film was prepared from chemical bath containing SbCl 3 and Na 2 S 2 O 3 , Ag 2 Se from the bath containing AgNO 3 and Na 2 SeSO 3 and Se thin films from an acidified solution of Na 2 SeSO 3 , at room temperature on cleaned glass substrates. Ag thin film was deposited by vacuum thermal evaporation. The annealing temperature was varied from 300-390°C in vacuum (∼10 −3 Torr) for 1 h. X-ray diffraction analysis showed the films formed at 350 °C was polycrystalline AgSb(S,Se) 2 or AgSbSe 2 depending on selenium thin film thickness. Morphology of these films was analyzed using Atomic Force Microscopy and Scanning Electron Microscopy. The elemental analysis was done using Energy Dispersive X-ray technique. Optical characterization of the thin films was done by optical transmittance spectra. The electrical characterizations were done using Hall effect and photocurrent measurements. A photovoltaic structure: Glass/ITO/CdS/AgSbSe 2 /Ag was formed, in which CdS was deposited by chemical bath deposition. J-V characteristics of this PV structure showed V oc =370 mV and J sc =0.5 mA/cm 2 under illumination using a tungsten halogen lamp.

Chemical Characterization of DC-Sputtered In2O3 Films with a Top SnO2 Layer

In2O3 thin films with a top layer of SnO2 were deposited onto glass substrates by DC reactive-magnetron sputtering. After deposition, In2O3/SnO2 samples were annealed in vacuum at 400oC. Structural, optical, and chemical composition was investigated by X-ray diffraction, UV-Vis spectroscopy and XPS, respectively. X-ray data showed that films grow polycrystalline, where indium oxide crystallized in cubic as the main phase, with a preferential growth at the [0002] direction and lattice parameter of 10.11 Å. Signals of rhombohedral phase were also detected. XPS depth profiles show that tin coexists in Sn2+ and Sn4+, while indium maintains the In2O3 stoichiometry. Binding energy of Sn4+ bound to oxygen was detected at 468 eV while In2+ bound to oxygen at 444.7 eV. Nor tertiary compounds were detected at the In2O3/SnO2 interface, neither In or Sn in metallic state.

INDIUM SELENIDE THIN FILMS BY LASER IRRADIATION OF In/Se LAYERED STRUCTURE

In this work, we report the formation of In6Se7 thin films by laser irradiation of In/Se layered structure. Indium layer was deposited on glass substrates by thermal evaporation on which selenium thin film was grown by chemical bath deposition from an aqueous solution containing 10 ml of sodium selenosulphate (0.1 M), 1.0 ml acetic acid (25%) and 70 ml distilled water during 5 min. The In/Se coated glass substrates were irradiated using a 532 nm continuous laser for 3–5 min. Structure, morphology, optical and electrical properties of the irradiated thin films were analyzed using various techniques. X-ray diffraction analysis showed that the irradiated thin films were In6Se7 of monoclinic structure. X-ray photoelectron spectroscopic study on the laser irradiated samples provided uniform relative composition of In and Se in the thin films formed after laser irradiation. The morphology, optical and electrical properties of the irradiated samples were investigated. The optical band gap of the In6Se7 thin films was 2.2 eV and also, the thin films were photoconductive.

Impact of activator incorporation on red emitting rods of ZnGa2O4:Cr3+ phosphor

Chromium doped zinc gallium oxide (ZnGa2O4:Cr3+) microrods were synthesized by simple solid state reaction method. The transformation on crystal structure and optical properties with molar concentration of Cr3+ were analyzed. The cubic spinel nature of ZnGa2O4:Cr3+phosphor and their crystalline nature were confirmed from x- ray diffractogram. The average grain size of the samples range between 24 and 29 nm, with lattice parameter values greater than that of bulk. Lattice strain produced in the lattice on doping was estimated from the Williamson-Hall plot. It increases on Cr3+ doping up to 3 mol% and then decreases. Rod like nature of zinc gallate was observed from the surface morphological analysis using SEM. X-ray photoelectron spectroscopy was used for the chemical state identification of the constituent elements in the compound. The photoluminescense spectra consists of various emission lines originated from the chromium ion in the spinel lattice. The purity of red emissions were observed from chromaticity diagram with a concentration quenching initiated from the dipole-dipole interaction, with increase in dopant concentration. Band gap of the samples were estimated using Kubelka-Munk equation which exhibited red shift compared to bulk due to band tailing effect.