Advanced Spray Pyrolysis Technique Research Articles

Effective role of thickness on structural, electrical and optical properties of lead sulphide thin films for photovoltaic applications

The n-type lead sulphide thin films were deposited at 350°C substrate temperature on glass substrates using advanced spray pyrolysis technique. The thickness of the thin films played an important role to improve the properties of lead sulphide and to use in device fabrication apart from various deposition parameters. The films deposited at thickness of 520nm resulted in a well oriented polycrystalline with face-centered cubic structure. An enhancement in the crystallite size with increase in film thickness was evidenced by XRD and SEM. The variation in crystallite size of films associated with different thickness provides a significant control over optical and electrical properties. The resistivity of the thin films decreased with an increase in thickness was of the order of 102Ωcm. The activation energy and optical band gap of the films deposited at optimized condition were found to be 0.20eV and 1.22eV, respectively. The absorption coefficient of the films was found to be 106cm−1. Results prove that the lead sulphide films synthesized using spray technique appeal its adaptability for potential photovoltaic applications in solar cells.

H2S gas sensitive Sn-doped ZnO thin films: Synthesis and characterization

Tin doped zinc oxide thin films were synthesized at low substrate temperature (473K) by advanced spray pyrolysis technique for H2S gas sensing application. Equimolar solution of zinc acetate and tin chloride were used to grow Sn doped ZnO thin films. The effects of tin doping concentration on the structural, morphological, and gas sensing properties of Sn doped ZnO films were investigated. It is revealed that all films exhibit wurtzite structure and the average crystallite size reduce with increasing Sn doping concentration. With an increase in Sn doping, the peak position of the (002) plane was shifted to the low 2θ values indicating the lattice distortion incorporated into the film due to Sn doping. The results obtained from TEM and FESEM characterizations confirmed the XRD observations. Further, the as-characterized Sn doped ZnO films were profoundly studied for their H2S sensing performance. The H2S gas sensing characteristics that are mainly governed by an operating temperature were found to be optimum at 473K. A maximum response of ∼31% to 30ppm H2S was obtained at 473K with reasonably fast response and recovery. Particularly, the 4wt.% Sn doped ZnO sample exhibits selective behavior towards H2S on account of its surface morphological features. The H2S detection properties of the 4wt.% Sn doped ZnO film were improved significantly on palladium (Pd) sensitization and the film demonstrated adequately stable sensing performance.

H2S gas sensing properties of nanocrystalline Cu-doped ZnO thin films prepared by advanced spray pyrolysis

The ZnO-based thin films doped with 1–4wt% Cu were deposited on the glass substrates using the advanced spray pyrolysis technique. All films are deposited at 473K. The crystallinity and morphology of the films were characterized by XRD, TEM and FE-SEM respectively. The structural analyses of the films indicate that they are polycrystalline and have a hexagonal wurtzite structure; however Cu doping enhances the preferential orientation along the [002]. The energy dispersive X-ray spectroscopic analysis (EDX) confirmed an enhancement in the amount of Cu in the film with increase in the copper concentration in the starting solution. The sensor response was estimated by the change in the electrical conductance of the film in the absence and presence of H2S gas. The sensor response and selectivity in relation to, operation temperature, Cu doping concentration and the gas concentration has been systematically studied. A significant response (∼0.38) towards 20ppm H2S at 523K operating temperature is observed for the 4wt% Cu-doped ZnO. The Pd-sensitized 4wt% Cu doped ZnO film exhibits improved sensing characteristics with good stability.

Influence of Substrate Temperature on ${\rm H}_{2}{\rm S}$ Gas Sensing Properties of Nanocrystalline Zinc Oxide Thin Films Prepared by Advanced Spray Pyrolysis

In this paper, nanocrystalline zinc oxide (ZnO) films are deposited onto glass substrates by a novel advanced spray pyrolysis technique, using non-aqueous zinc acetate solution. ZnO films are grown at various substrate temperatures in the range of 423-523 K, keeping the reaction chamber temperature constant. The influence of substrate temperature on film crystallinity and surface morphology electrical properties are investigated. The films are found to be polycrystalline with a wurtzite hexagonal structure. Surface morphological studies reveal columnar growth with enhanced crystallinity and lower activation energy at higher substrate temperature. The H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S gas sensing properties of ZnO films are studied as a function of substrate temperature, operating temperature, and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S gas concentration. The film grown at a 523 K substrate temeprature exhibits maximum sensitivity (~22%) to 20-ppm H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S exposure at a 573-K working temperature and exhibits good selectivity and stability.

Structural and photoluminescence characterization of SnO2: F thin films deposited by advanced spray pyrolysis technique at low substrate temperature

Fluorine doped tin oxide (FTO) thin films were deposited on glass substrates, at different substrate temperatures using advanced spray pyrolysis technique. X-ray diffraction studies showed that the crystallinity of the thin films increased with increasing substrate temperature. FESEM and AFM studies support the conclusions drawn from X-ray diffraction studies. X-ray photoelectron studies confirm oxygen deficiency in formation of the FTO nanocrystallites. The photoluminescence of the FTO films were investigated. It was found that, room temperature photoluminescence spectra are dominated by oxygen vacancies and exhibit a rich violet photoluminescence band about ∼404nm with an extensively feeble red emission about 700nm. The Photoluminescence intensity varies with the substrate temperature. The photoemission position is observed to be independent of substrate temperature.

Thickness dependent H2S sensing properties of nanocrystalline ZnO thin films derived by advanced spray pyrolysis

Undoped zinc oxide (ZnO) thin films with various thicknesses were deposited onto glass substrates by advanced spray pyrolysis technique by varying the volume of spray solution. All the films were deposited at 473 K substrate temperature. These samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques, respectively. The X-ray diffraction analysis reveals that film growth is preferentially along (0 0 2) plane and thickness independent. All films exhibit hexagonal wurtzite structure, however, noticeable change is observed in crystallite size. An enhancement in the grain size with increase in film thickness was observed from the SEM studies. A two probe resistivity measurements exhibit decrease in resistivity with increase in film thickness. The response of ZnO samples toward H2S gas has been investigated at different operating temperatures and gas concentrations. Highest sensitivity was obtained for the film with 135 nm film thickness at 20 ppm H2S concentration when operating temperature is 573 K. The observed variation in sensitivity is related to the change in grain size with variation in film thickness.

Influence of core temperature on physical and H2S sensing properties of zinc oxide thin films

Nanocrystalline Zinc oxide (ZnO) thin films were deposited onto glass at low substrate temperature using advanced spray pyrolysis technique, with zinc acetate as precursor. The films were grown at various core temperatures in the range of 548–648K. Influence of the core temperature on the crystalline, surface morphological and electrical properties of the films have been investigated. XRD studies show that films prepared at core temperatures ⩾598K are polycrystalline and have a wurtzite crystal structure. FE-SEM micrograph observations of the films support the XRD results. The temperature dependence of the electrical resistivity was studied using two-probe method. It was observed that ZnO films exhibit semiconducting behavior. Further, the gas sensing potential of ZnO films towards H2S was examined. The sensing performance was studied at various operating temperatures and gas concentrations. The film deposited at 598K show a good sensing response (∼19%) and selectivity to H2S at an optimal working temperature.

Preparation of fluorine-doped tin oxide films at low substrate temperature by an advanced spray pyrolysis technique, and their characterization

Indispensable fluorine-doped tin oxide thin films were prepared on glass substrates by an advanced spray pyrolysis technique at low substrate temperature, with stannic chloride (SnCl4⋅5H2O) and ammonium fluoride (NH4F) as precursors. The films were grown at different substrate temperatures varied in the range of 523–613 K. The influence of the substrate temperature on the structural, morphological, optical and electrical properties of the films has been investigated. XRD studies show that all the films are polycrystalline and have a tetragonal crystal structure. The films deposited at the 613 K substrate temperature exhibit the lowest sheet resistance (17.82 Ω) with optical transmittance of ∼75% (at 550 nm). Hall-effect measurements showed that the films are heavily doped degenerate semiconductors with n-type electrical conductivity.