Bindu Krishnan

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.

Growth and properties of lead iodide thin films by spin coating

In this study, lead iodide (PbI2) thin films were deposited on glass substrates by spin coating a solution of 0.2 M PbI2 dissolved in dimethylformamide, varying the deposition time and the spin speed. The thickness of the thin films decreased with increase in spin speed and deposition time, as examined by profilometry measurements. The structure, morphology, optical and electrical properties of the thin films were analysed using various techniques. X-ray diffraction patterns revealed that the thin films possessed hexagonal structures. The thin films were grown highly oriented to [001] direction of the hexagonal lattice. Raman peaks detected at 96 and 136 cm−1 were corresponding to the characteristic vibration modes of PbI2. The X-ray photoelectron spectroscopy detected the presence of Pb and I with core level binding energies corresponding to that in PbI2. Atomic force microcopy showed smooth and compact morphology of the thin films. From UV–Vis transmittance and reflectance spectral analysis, the bandgap of the thin films ∼2.3 eV was evaluated. The dark conductivity of the thin films was computed and the value decreased as the deposition time and spin speed increased.

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.

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.

Nanostructured SnS2 Thin Films from Laser Ablated Nanocolloids: Structure, Morphology, Optoelectronic and Electrochemical Properties

Tin disulfide (SnS2 ) is a binary chalcogenide semiconductor having applications in solar cells, energy storage, and optoelectronics. SnS2 thin films were deposited by spraying the nanocolloids synthesized by pulsed laser ablation in liquid. The structure, morphology, and optoelectronic properties were studied for films obtained from two liquid media (ethanol and isopropanol) and after heat treatments at various temperatures. X-ray diffraction analysis confirmed the hexagonal crystal structure of the films, whereas the 2-H polytype structure was identified by micro-Raman spectroscopy. Oxidation states of Sn (4+) and S (2-) identified from high resolution X-ray photoelectron spectra confirmed the composition and chemical states of the films. The SnS2 thin films exhibited distinct porous surface morphologies as the liquid medium in laser ablation was varied. All as-prepared and annealed films showed photoluminescence with a high intensity peak at 485 nm and a low intensity peak at 545 nm. Thin films annealed at 300 °C showed improved electrochemical properties upon illumination using a blue LED light source. Current-voltage curves recorded in dark and light as well as the photoresponse measurements showed their suitability for utilization in optoelectronic devices. The results of this study may trigger further research towards fabrication of nanostructured thin films in large area for optoelectronic and photoelectrochemical applications in an environment friendly and cost-effective way.