Highly conductive and transparent ZnO thin film using Chemical Spray Pyrolysis technique: Effect of doping and deposition parameters

In the present work we report the preparation details studies on ZnO thin films. ZnO thin films are prepared using cost effective deposition technique viz., Chemical Spray Pyrolysis (CSP). The method is very effective for large area preparation of the ZnO thin film. A new post-deposition process could also be developed to avoid the adsorption of oxygen that usually occurs after the spraying process i.e., while cooling. Studies were done by changing the various deposition parameters for optimizing the properties of ZnO thin film. Moreover, different methods of doping using various elements are also tried to enhance the conductivity and transparency of the film to make these suitable for various optoelectronic applications.

Optimization of parameters of chemical spray pyrolysis technique to get n and p-type layers of SnS

SnS thin films were prepared using automated chemical spray pyrolysis (CSP) technique. Single-phase, p-type, stoichiometric, SnS films with direct band gap of 1.33 eV and having very high absorption coefficient (N105/cm) were deposited at substrate temperature of 375 °C. The role of substrate temperature in determining the optoelectronic and structural properties of SnS films was established and concentration ratios of anionic and cationic precursor solutions were optimized. n-type SnS samples were also prepared using CSP technique at the same substrate temperature of 375 °C, which facilitates sequential deposition of SnS homojunction. A comprehensive analysis of both types of films was done using x-ray diffraction, energy dispersive x-ray analysis, scanning electron microscopy, atomic force microscopy, optical absorption and electrical measurements. Deposition temperatures required for growth of other binary sulfide phases of tin such as SnS2, Sn2S3 were also determined

Development of uniformly grown ZnO NPs films using single precursor solution by pulsed spray pyrolysis technique

In this article, we have reported the controlled synthesis of uniformly grown zinc oxide nanoparticles (ZnO NPs) films by a simple, low-cost, and scalable pulsed spray pyrolysis technique. From the surface analysis it is noticed that the as-deposited films have uniformly dispersed NPs-like morphology. The structural studies reveal that these NPs films have highly crystalline hexagonal crystal structure, which are preferentially orientated along the (001) planes. The size of the NPs varied between 5 and 100 nm, and exhibited good stoichiometric chemical composition. Raman spectroscopic analysis reveals that these ZnO NPs films have pure single phase and hexagonal crystal structure. These unique nanostructured films exhibited a low electrical resistivity (5 Omega cm) and high light transmittance (90 %) in visible region.

Nanostructured GdxZn1-xO thin films by nebulizer spray pyrolysis technique: Role of doping concentration on the structural and optical properties

Nanostructured GdxZn1-xO thin films with different Gd concentration from 0% to 10% deposited at 400 degrees C using the NSF technique. The films were characterized by structural, surface and optical properties, respectively. X-ray diffraction analysis shows that the Gd doped ZnO films have lattice parameters a = 3.2497 angstrom and c = 5.2018 angstrom with hexagonal structure and preferential orientation along (002) plane. The estimated values compare well with the standard values. When film thickness increases from 222 to 240 nm a high visible region transmittance (>70%) is observed. The optical band gap energy, optical constants (n and k), complex dielectric constants (epsilon(r), and epsilon(i)) and optical conductivities (sigma(r), and sigma(i)) were calculated from optical transmittance data. The optical band gap energy is 3.2 eV for pure ZnO film and 3.6 eV for Gd0.1Zn0.9-O film. The PL studies confirm the presence of a strong UV emission peak at 399 nm. Besides, the UV emission of ZnO films decreases with the increase of Gd doping concentration correspondingly the ultra-violet emission is replaced by blue and green emissions.

Role of substrate temperature on the properties of Na-doped ZnO thin film nanorods and performance of ammonia gas sensors using nebulizer spray pyrolysis technique

Sodium doped zinc oxide (Na:ZnO) thin films were deposited on glass substrates at substrate temperatures 300,400 and 500 degrees C by a novel nebulizer spray method. X-ray diffraction shows that all the films are polycrystalline in nature having hexagonal structure with high preferential orientation along (0 0 2) plane. High resolution SEM studies reveal the formation of Na-doped ZnO films having uniformly distributed nano-rods over the entire surface of the substrates at 400 degrees C. The complex impedance of the ZnO nano-rods shows two distinguished semicircles and the diameter of the arcs got decreased in diameter as the temperature increases from 170 to 270 degrees C and thereafter slightly increased. (c) 2013 Elsevier B.V. All rights reserved.

Growth of AgInS2 thin films by ultrasonic spray pyrolysis technique

Silver Indium Di-sulfide (AgInS2) thin films are deposited using ultrasonic spray pyrolysis technique and the effect of substrate temperature (T-s) on film growth is studied by varying the temperature from 250 to 400 degrees C. From the structural analysis, orthorhombic AgInS2 phase is identified with preferential orientation along (002) plane. Further analysis with Raman revealed the coexistence of Cu-Au ordered and chalcopyrite structures in the films. Stoichiometric films are obtained at T-s of 300 degrees C. Above 300 degrees C, the film conductivity changed from p to n-type and the grain size decreased. The band gap of AgInS2 films varied from 1.55 to 1.89 eV and absorption coefficient is found to be >10(4) cm(-1). The films have sheet resistance in the range of 0.05 to 1300 Omega/square Both p and n type films are prepared through this technique without any external doping. (C) 2013 Elsevier B.V. All rights reserved.

Automation of Chemical Spray Pyrolysis Unit and Fabrication of Sprayed CuInS2/In2S3 Solar Cell

Aim of the present work was to automate CSP process, to deposit and characterize CuInS2/In2S3 layers using this system and to fabricate devices using these films.An automated spray system for the deposition of compound semiconductor thin films was designed and developed so as to eliminate the manual labour involved in spraying and facilitate standardization of the method. The system was designed such that parameters like spray rate, movement of spray head, duration of spray, temperature of substrate, pressure of carrier gas and height of the spray head from the substrate could be varied. Using this system, binary, ternary as well as quaternary films could be successfully deposited.The second part of the work deal with deposition and characterization of CuInS2 and In2S3 layers respectively.In the case of CuInS2 absorbers, the effects of different preparation conditions and post deposition treatments on the optoelectronic, morphological and structural properties were investigated. It was observed that preparation conditions and post deposition treatments played crucial role in controlling the properties of the films. The studies in this direction were useful in understanding how the variation in spray parameters tailored the properties of the absorber layer. These results were subsequently made use of in device fabrication process.Effects of copper incorporation in In2S3 films were investigated to find how the diffusion of Cu from CuInS2 to In2S3 will affect the properties at the junction. It was noticed that there was a regular variation in the opto-electronic properties with increase in copper concentration.Devices were fabricated on ITO coated glass using CuInS2 as absorber and In2S3 as buffer layer with silver as the top electrode. Stable devices could be deposited over an area of 0.25 cm2, even though the efficiency obtained was not high. Using manual spray system, we could achieve devices of area 0.01 cm2 only. Thus automation helped in obtaining repeatable results over larger areas than those obtained while using the manual unit. Silver diffusion on the cells before coating the electrodes resulted in better collection of carriers.From this work it was seen CuInS2/In2S3 junction deposited through automated spray process has potential to achieve high efficiencies.

Polycrystalline Lead Tin Chalcogenide Thin Film Grown by Spray Pyrolysis

PbSnS2 thin film has been prepared for the first time by spray pyrolysis technique on FTO substrate at 570K. The preliminary optical and structural characteristics of the film have been reported. The optical studies showed that the value of the fundamental absorption edge lies at 1.47eV and a low energy absorption band tail has been observed. The prepared film is p- type electrical conductivity, polycrystalline in nature and has an orthorhombic crystal structure. The value of an average grain size of the film is 350Å.

Tin-Incorporation Induced Changes in the Microstructural, Optical, and Electrical Behavior of Tungsten Oxide Nanocrystalline Thin Films Grown Via Spray Pyrolysis

Undoped and Sn-doped WO3 thin films were grown on cleaned glass substrates by chemical spray pyrolysis, using ammonium tungstate (NH4)(2)WO4 as the host precursor and tin chloride (SnCl4 center dot 5H(2)O) as the source of dopant. The XRD spectra confirm the monoclinic structure with a sharp narrow peak along (200) direction along with other peaks of low relative intensities for all the samples. On Sn doping, the films exhibit reduced crystallinity relative to the undoped film. The standard deviation for relative peak intensity with dopant concentration shows enhancement in heterogeneous nucleation growth. As evident from SEM images, on Sn doping, appearance of island-like structure (i.e., cluster of primary crystallites at few places) takes place. The transmittance has been found to decrease in all the Sn-doped films. The optical band gap has been calculated for both direct and indirect transitions. On Sn doping, the direct band gap shows a red shift and becomes 2.89 eV at 2 at.% doping. Two distinct peaks, one blue emission at 408 nm and other green emission at 533 nm, have been found in the PL spectra. Electrical conductivity has been found to increase with Sn doping.

Metal-insulator transition characteristics of vanadium dioxide thin films synthesized by ultrasonic nebulized spray pyrolysis of an aqueous combustion mixture

We report the synthesis of high quality vanadium dioxide (VO2) thin films by a novel spray pyrolysis technique, namely ultrasonic nebulized spray pyrolysis of aqueous combustion mixture (UNSPACM). This simple and cost effective two step process involves synthesis of a V2O5 film on an LaAlO3 substrate followed by a controlled reduction to form single phase VO2. The formation of M1 phase (p21/c) is confirmed by Raman spectroscopic studies. A thermally activated metal-insulator transition (MIT) was observed at 61 degrees C, where the resistivity changes by four orders of magnitude. Activation energies for the low conduction phase and the high conduction phase were obtained from temperature variable resistance measurements. The infrared spectra also show a dramatic change in reflectance from 13% to over 90% in the wavelength range of 7-15 mu m. This indicates the suitability of the films for optical switching applications at infrared frequencies.

CuInS2 thin films using chemical methods for the fabrication of CuInS2/CdS solar cells

Dept.of Physics, Cochin University of Science and Technology

Strontium titanate films prepared by spray pyrolysis

Strontium titanate thin films were prepared by spray pyrolysis technique. Deposition parameters, such as solution concentration, time and temperature of deposition, and flow rate of carrier gas were optimized to obtain dense films without cracks. Films with different thicknesses were prepared through the control of deposition time. Prepared thin films were homogeneous, well crystallized, with uniform grain size. (C) 2003 Elsevier Ltd. All rights reserved.

Oriented films of LaNiO3 and other members of the Lan+1NinO3n+1 series, LaCuO3−δ and Pb(Zr0.52Ti0.48)O3, obtained by nebulized spray pyrolysis

The technique of nebulized spray pyrolysis has been explored to find out whether oriented films of certain important oxides can be produced on single-crystal substrates by this relatively gentle method. Starting with acetylacetonate precursors, oriented films of metallic LaNiO3 containing nearly spherical grains (30 nm) have been obtained. Films of near-stoichiometric La4Ni3O10 and La3Ni2O7 showing metallic conductivity have been obtained by this method. This is indeed gratifying since it is difficult to prepare monophasic and stoichiometric bulk samples of these materials. Films of La2NiO4 show the expected semiconducting behavior. In the La-Cu-O system, starting with acetylacetonates, we have obtained films mainly comprising semiconducting La2Cu2O5, which is generally difficult to prepare in bulk form. More interestingly, nebulized spray pyrolysis gives excellent stoichiometric films of Pb(Zr0.52Ti0.48)O-3 consisting of nearly spherical grains (30 nm) which show ferroelectric behavior. The present investigation demonstrates that nebulized spray pyrolysis provides a useful and desirable route to deposite oriented films of complex oxide materials on single-crystal substrates.

Effect of doping concentration on the structural and optical properties of pure and tin doped zinc oxide thin films by nebulizer spray pyrolysis (NSP) technique

Pure and tin doped zinc oxide (Sn:ZnO) thin films were prepared for the first time by NSP technique using aqueous solutions of zinc acetate dehydrate, tin (IV) chloride fendahydrate and methanol. X-ray diffraction patterns confirm that the films are polycrystalline in nature exhibiting hexagonal wurtzite type, with (0 0 2) as preferred orientation. The structural parameters such as lattice constant ('a' and `c'), crystallite size, dislocation density, micro strain, stress and texture coefficient were calculated from X-ray diffraction studies. Surface morphology was found to be modified with increasing Sn doping concentration. The ZnO films have high transmittance 85% in the visible region, and the transmittance is found to be decreased with the increase of Sn doping concentration. The corresponding optical band gap decreases from 3.25 to 3.08 eV. Room temperature photoluminescence reveals the sharp emission of strong UV peak at 400 nm (3.10 eV) and a strong sharp green luminescence at 528 nm (2.34 eV) in the Sn doped ZnO films. The electrical resistivity is found to be 10(6) Omega-cm at higher temperature and 10(5) Omega-cm at lower temperature. (C) 2012 Elsevier Ltd. All rights reserved.