Electrical resistivity and photoluminescence of zinc oxide films prepared by ultrasonic spray pyrolysis

Abstract

Zinc oxide (ZnO) thin films have been prepared by ultrasonic Spray pyrolysis (USP) technique using zinc acetate dihydrate dissolved in methanol, ethanol and deionized water. A number of techniques, including X‐ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, UV–visible, electrical resistivity, and photoluminescence (PL) were used to characterize the obtained ZnO thin films. The evolution of the preferred crystalline orientations in the ZnO films was systematically investigated. The PL measurements indicated that the as‐grown ZnO thin films showed UV and green emission bands when they were excited by a Hg arc lamp using 313 nm as the excitation source. A red‐shift in the near band edge (NBE) has been observed with the increase in the substrate temperature and has been attributed to the compressive intrinsic stress present in the films. It is confirmed that oxygen vacancy (VO) is the most important factor that causes the broad visible emission. Furthermore, the visible emission and electrical resistivity of ZnO thin films are found to be a function of porosity. Also, it has been interestingly found that the intensity of green emission at ∼2.5 eV remarkably increased when the obtained ZnO films were deposited at 320 °C. The reason might be the VO, intrinsic stress, surface‐to‐volume ratio and porosity in the sample increased at low substrate temperature. The resistivity follows the same behavior as the intensity of the green emission. We propose a new luminescence mechanism based on the recombination related to oxygen vacancies in Zn‐rich or stoichiometric conditions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Low temperature synthesis and properties of MgxZn1−x O:Al UV transparent conducting films by ultrasonic spray pyrolysis

“…When the Mg doping content x is 0.4, most grains are lenticular-like which have a high aspect ratio of 5:6. Similar grain morphology of ZnO films was observed by Bouzid et al [9].…”

“…Many techniques, including PLD [3], magnetron sputtering [4] and sol-gel [5], have been employed to synthesize Mg x Zn 1-x O thin films. Ultrasonic spray pyrolysis (USP) is an important technique for preparing large-area thin films with low cost, which has been used successfully to synthesize high quality non-doped or doped ZnO thin films [8,9]. In this work, the preparation of Mg x Zn 1-x O:Al films synthesized by ultrasonic spray pyrolysis is described, and the effects of Mg doping content and substrate temperature on electrical and optical properties are studied.…”

Structural, microstructural, and optical properties of Zn1−x Mg x O thin films grown onto glass substrate by ultrasonic spray pyrolysis

“…In this research work, the rapid evaporation-oxidation process, V O , should be generated because of partially incomplete oxidation and crystallinity. In addition, ZnO grains with high aspect ratio (nanorods and nanopetals) should also favor the existence of high density of V O [32,33].…”

“…1-x Mg x O thin films grown onto glass… 753attributed to the neutral oxygen vacancies within ZnO[32]. For instance, the luminescence intensity at 2.63 eV of Zn 0.85 Mg 0.15 O thin film is approximately 13 times higher than that of undoped ZnO film measured under the same excitation conditions.…”

Resistivity Stability of Ga Doped ZnO Thin Films with Heat Treatment in Air and Oxygen Atmospheres

“…The band-to-band excitation of ZnO promotes electrons from the valence band to the conduction band, leaving holes in the valence band [36]. The holes migrate from the valence band to deep levels and recombination occurs between electrons from either the conduction band or shallow donor levels and trapped holes on deep levels [37].…”