Elsevier

Applied Surface Science

Volume 252, Issue 24, 15 October 2006, Pages 8745-8750
Applied Surface Science

Effect of solution molarity on the characteristics of vanadium pentoxide thin film

https://doi.org/10.1016/j.apsusc.2005.12.076Get rights and content

Abstract

Vanadium pentoxide (V2O5) thin films have been prepared by spray pyrolysis technique. The influence of solution molarity on the characteristics of the V2O5 has been investigated. X-ray diffraction analysis (XRD) showed that, the films deposited at ≥0.1 M were orthorhombic structure with a preferential orientation along 〈0 0 1〉 direction. Moreover, the crystallinity was improved by increasing solution molarity. The microstructure parameters have been evaluated by using a single order Voigt profile method. The optical band gaps, determined by using Tauc plot, have been found to be 2.50 ± 0.02 and 2.33 ± 0.02 eV for the direct and indirect allowed transition, respectively. Also the complex optical constants for the wavelength range 300–2500 nm are reported. At room temperature, the dark conductivity as a function of solution molarity showed the range of 5.74 × 10−2 ± 0.03 to 3.36 × 10−1 ± 0.02 Ω−1 cm−1. While at high temperature, the behaviour of electrical conductivity dominated by grain boundaries. The values of activation energy and potential barrier height were 0.156 ± 0.011 and 0.263 ± 0.012 eV, respectively.

Introduction

Nowadays vanadium pentoxide films are of increasing interest due to their unique features, such as electro-chemical activity, high stability, good specific energy, special layer structure and high capacity as well as excellent thermoelectric property. It can be used as a gas sensor, cathode for solid-state batteries, window for solar cells and as an active material in electrochromic devices [1], [2]. There are many numbers of vanadium oxides and suboxides such as VO, V2O3, VO2, V4O9 and V2O5. Most of these oxides are metal–insulator transition, which occurs over a wide range of transition temperature depending on the O/V ratio. Vanadium pentoxide is the most stable compound of the V–O system [3]. Various methods are reported for the preparation of V2O5 thin films such as vacuum evaporation [4], [5], RF sputtering [2], chemical vapour deposition [6], electron beam evaporation [7] and pulsed laser deposition (PLD) [8]. However, the deposition of thin film from sprayed solution catch the attention of researchers because of such method has low-cost set-up and has the ability to deposit large area [9]. In this work, the synthesis of V2O5 films by spray pyrolysis technique was investigated at different concentrations of spray solution at constant substrate temperature. The influence of solution molarity on the characteristics (microstructures, optical and electrical properties) of V2O5 thin film is reported.

Section snippets

Experimental details

At constant temperature, different concentrations of vanadium nitrate [V(NO3)5·5H2O] namely 0.1, 0.2, 0.3, 0.4 and 0.5 M were sprayed on preheated amorphous glass substrates. The substrates have been chemically and ultrasonically pre-cleaned. In order to get uniform thin films, a suitable condition for the height of the spraying nozzle, the flow rate and the deposition time are chosen and kept unchanged during the deposition process at 27 cm, 5 cm3 min−1 and 45 s, respectively. Also, a compressed

Structural characterization

Fig. 1 shows the X-ray diffraction (XRD) patterns for samples prepared at Tsub = 350 °C with different solution molarities, namely 0.1, 0.2, 0.3, 0.4 and 0.5 M. The peaks are indexed in comparing our experimental data with the ASTM cards of X-ray powder. The produced data for all films prepared at different molarities of spray solution showed a good agreement with the data of V2O5 powder file (JCPDS data number 09-0387) which corresponding to the orthorhombic crystalline structure. Indeed, the

Conclusions

In the present investigation vanadium pentoxide films deposited by spray pyrolysis at different solution molarities exhibit some interesting microstructural, optical and electrical properties. The X-ray diffraction (XRD) revealed that, the prepared films at solution molarity ≥0.1 M and Tsub = 350 °C was polycrystalline orthorhombic structure with a preferential orientation along 〈0 0 1〉 direction. The values of crystallite size increased with increasing solution molarity from 0.1 to 0.4 M.

References (25)

  • M. Benmoussa et al.

    Thin Solid Films

    (2002)
  • L. Ottaviano et al.

    Opt. Mater.

    (2004)
  • G. Wu et al.

    Thin Solid Films

    (2005)
  • R.T. Rajendra Kumar et al.

    Mater. Sci. Semi. Proc.

    (2003)
  • A. Bouzidi et al.

    Mater. Sci. Eng.

    (2002)
  • N. Kenny et al.

    J. Phys. Chem. Solids

    (1966)
  • T. Maruyama et al.

    Thin Solid Films

    (1990)
  • T. Rechardson, K. von Rottkay, J. Slack, F. Michalak, M. Rubin, Ernest Orlando Lawrence Berkeley National Laboratory,...
  • P. Chatterjee et al.

    Bull. Mater. Sci.

    (2001)
  • B.N.B. Thi et al.

    J. Appl. Phys.

    (1996)
  • K.V. Madhuri et al.

    J. Indian Inst. Sci

    (2001)
  • C.V. Ramana et al.

    J. Phys. D: Appl. Phys.

    (2001)
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