Experimental Investigation of Spray-Deposited Fe-Doped ZnO Nanoparticle Thin Films: Structural, Microstructural, and Opt
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JTTEE5 22:1230–1241 DOI: 10.1007/s11666-013-9973-0 1059-9630/$19.00 ASM International
Experimental Investigation of Spray-Deposited Fe-Doped ZnO Nanoparticle Thin Films: Structural, Microstructural, and Optical Properties C. S. Prajapati, Ajay Kushwaha, and P. P. Sahay (Submitted May 4, 2013; in revised form July 22, 2013) Structural, microstructural, and optical properties of the undoped and Fe-doped zinc oxide (ZnO) thin films grown by spray pyrolysis technique using zinc nitrate as a host precursor have been reported here. X-ray diffraction spectra confirm that all the films have stable wurtzite structure and the effects of Fe dopants on the diffraction patterns have been found to be in agreement with the Vegards law. Scanning electron microscopy results show good uniformity and dense surface having spherical-shaped grains. Energy dispersive x-ray analyses with elemental mapping of the Fe-doped films show that the Fe dopants are incorporated homogeneously into the ZnO film matrix. The x-ray photoelectron spectroscopy spectra confirm the presence of 3+ oxidation state of Fe in the doped films. Atomic force microscopy analyses clearly show that the average surface roughness and the grain size decrease with the addition of Fe dopants. Optical studies reveal that the optical band gap value decreases on Fe doping. The 1 at.% Fedoped film shows normal dispersion for the wavelength range 450-700 nm. The PL spectra of the films show a strong ultraviolet emission centered at ~388 nm in the case of 1 at.% Fe-doped film. A slow photo current response in the films has been observed in the transient photoconductivity measurement.
Keywords
Fe-doping, optical properties, surface morphology, ZnO nanoparticle thin films
1. Introduction Zinc oxide (ZnO), a wide band gap (3.36 eV at 300 K) compound semiconductor, has a stable wurtzite structure and high exciton binding energy of 60 meV (Ref 1). It has drawn the attention of many researchers because of its unique properties such as high thermal stability, non-toxicity in nature, high transparency in visible region, good phosphor material, etc. Because of its multifunctional properties (semiconducting, magnetic, piezoelectric, etc.), this material has got wide applications in various electronic and optoelectronic devices such as in transparent electrodes, solar cell windows, thin film transistor, chemical sensors, etc. (Ref 2-6). ZnO has been exploited in various forms such as single crystal, sintered pellets, thick films, thin films, and hetero-junctions (Ref 7-11). However, thin films are more suitable for the chemical gas sensors because the gas sensing properties are related to C.S. Prajapati and P.P. Sahay, Department of Physics, Motilal Nehru National Institute of Technology, Allahabad 211004, India; and Ajay Kushwaha, Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India. Contact e-mail: [email protected].
1230—Volume 22(7) October 2013
the material surface, where the gases are adsorbed and the chemical reactions occur. Mor
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