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Synthesis and characterization of zinc oxide thin films for optoelectronic applications

View Article: PubMed Central - PubMed

ABSTRACT

Micro-ring structured zinc oxide (ZnO) thin films were prepared on glass substrates by spray pyrolysis and their structural, morphological, optical and electrical properties were investigated. X-ray Diffraction (XRD) analysis revealed the films’ hexagonal wurtzite phase with a preferred (002) grain orientation. The mean crystallite size calculated on the basis of the Debye-Scherrer model was 24 nm and a small dislocation density of 1.7×10−3  nm−2 was obtained, indicating the existence of few lattice defects and good crystallinity. Scanning Electron Microscopy (SEM) micrographs revealed the film’s granular nature composed of rod-shaped and spherical nanoparticles which agglomerated to form micro-ring like film clusters on the film surface. The average transmittance in the visible region, optical band gap and Urbach energy were approximately 75–80%, 3.28 eV and 57 meV, respectively. The refractive index and extinction coefficient were determined using Swanepoel’s envelope method. Raman spectroscopy revealed the presence of small amounts of residual tensile stress and low density of defects in the ZnO thin films. This was consistent with XRD analysis. A low sheet resistivity (6.03×101  Ωcm) and high figure of merit (4.35×10−6  Ω−1) were obtained for our films indicating their suitability in optoelectronic applications.

No MeSH data available.


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Optical transmission spectrum of the micro-ring structured ZnO thin film. The dotted curves for TM and Tm are the envelopes generated in the high transmission region.
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fig0015: Optical transmission spectrum of the micro-ring structured ZnO thin film. The dotted curves for TM and Tm are the envelopes generated in the high transmission region.

Mentions: Fig. 3 shows the transmittance spectrum of the ZnO micro-ring structured thin films. Fluctuations and wave-like patterns appeared on the transmittance spectrum due to the interference of light reflected between the air-film and film-glass interfaces, indicating the film’s low surface roughness and good uniformity [37]. The film had an average transparency of about 75–80% in the visible region which may be associated with the film’s good structural homogeneity and crystallinity [7]. This was higher than 20% [26] and 25% [27] for undoped ZnO microrods and 60% [15] for undoped ZnO microsausages. A sharp absorption edge was observed at approximately 375 nm and this was in fair agreement with Karakaya et al. [38] and Winer et al. [10]. This strong absorption correlates with the band gap at which incident photons will be having enough energy to cause electronic excitations across the band gap [38].


Synthesis and characterization of zinc oxide thin films for optoelectronic applications
Optical transmission spectrum of the micro-ring structured ZnO thin film. The dotted curves for TM and Tm are the envelopes generated in the high transmission region.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384418&req=5

fig0015: Optical transmission spectrum of the micro-ring structured ZnO thin film. The dotted curves for TM and Tm are the envelopes generated in the high transmission region.
Mentions: Fig. 3 shows the transmittance spectrum of the ZnO micro-ring structured thin films. Fluctuations and wave-like patterns appeared on the transmittance spectrum due to the interference of light reflected between the air-film and film-glass interfaces, indicating the film’s low surface roughness and good uniformity [37]. The film had an average transparency of about 75–80% in the visible region which may be associated with the film’s good structural homogeneity and crystallinity [7]. This was higher than 20% [26] and 25% [27] for undoped ZnO microrods and 60% [15] for undoped ZnO microsausages. A sharp absorption edge was observed at approximately 375 nm and this was in fair agreement with Karakaya et al. [38] and Winer et al. [10]. This strong absorption correlates with the band gap at which incident photons will be having enough energy to cause electronic excitations across the band gap [38].

View Article: PubMed Central - PubMed

ABSTRACT

Micro-ring structured zinc oxide (ZnO) thin films were prepared on glass substrates by spray pyrolysis and their structural, morphological, optical and electrical properties were investigated. X-ray Diffraction (XRD) analysis revealed the films’ hexagonal wurtzite phase with a preferred (002) grain orientation. The mean crystallite size calculated on the basis of the Debye-Scherrer model was 24 nm and a small dislocation density of 1.7×10−3  nm−2 was obtained, indicating the existence of few lattice defects and good crystallinity. Scanning Electron Microscopy (SEM) micrographs revealed the film’s granular nature composed of rod-shaped and spherical nanoparticles which agglomerated to form micro-ring like film clusters on the film surface. The average transmittance in the visible region, optical band gap and Urbach energy were approximately 75–80%, 3.28 eV and 57 meV, respectively. The refractive index and extinction coefficient were determined using Swanepoel’s envelope method. Raman spectroscopy revealed the presence of small amounts of residual tensile stress and low density of defects in the ZnO thin films. This was consistent with XRD analysis. A low sheet resistivity (6.03×101  Ωcm) and high figure of merit (4.35×10−6  Ω−1) were obtained for our films indicating their suitability in optoelectronic applications.

No MeSH data available.


Related in: MedlinePlus