ZnO wide bandgap semiconductors preparation for optoelectronic devices

Ramelan, Ari Handono; Wahyuningsih, Sayekti; Munawaroh, H; Narayan, Roger J.

doi:10.1088/1757-899x/176/1/012008

Cited by 22 publications

(9 citation statements)

References 16 publications

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“…A plot of this is shown in Figure 14; the two possible band gap values obtained suggested that the composite of ZnO-Zn 2 SnO 4 had transited to an indirect bandgap material. The result is further confirmed by the plot of (αhv) 1/2 againsthv in Figure 14 given only one [41,42]. This result indicates that the wide bandgap of the semiconductor ZnO and Zn 2 SnO 4 has transformed to a narrow bandgap material.…”

Section: Optical Band Gap Determinationsupporting

confidence: 55%

Effect of tin on bandgap narrowing and optical properties of ZnO–Zn₂SnO₄ electrospun nanofibre composite

Bolarinwa

Onuu

Animashaun

et al. 2020

Journal of Taibah University for Science

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The quest for improved visible light absorption in ZnO-based photocatalysts and photodetectors is a prevailing research problem. One method of solving this problem is by narrowing the band gap of this material well into the range of visible light energy. In this work, we have demonstrated considerable band narrowing into the visible region in our electrospun ternary ZnO-Zn 2 SnO 4 nanofibres. We also showed that band narrowing is highly dependent on the amount of Sn in the synthesized composite which could be attributed to the creation of localized states in the ZnO band and the attendant structural changes. However, beyond 15%wt doping there were observed changes in the trend of the bandgap reduction, crystallite sizes, and width of the localized states in the ternary ZnO-Zn 2 SnO 4 band. The details of experimental procedures and discussion of results have been included in this paper.

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Section: Optical Band Gap Determinationsupporting

confidence: 55%

Effect of tin on bandgap narrowing and optical properties of ZnO–Zn₂SnO₄ electrospun nanofibre composite

Bolarinwa

Onuu

Animashaun

et al. 2020

Journal of Taibah University for Science

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“…The calculated E g of the samples are listed in Table III. From the Table, it was observed that the value of E g in the undoped ZnO is ≈ 3.34 eV which is lower than its typical value of 3.37 eV [50]. The lower band gap of the undoped ZnO might be caused by the number of point defects (vacancies and interstitials of Zn and O) [51].…”

Section: Resultsmentioning

confidence: 90%

The Effects of Mn Doping on the Structural and Optical Properties of ZnO

Bilgili¹

2019

Acta Phys. Pol. A

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Zn1−xMnxO (x = 0.00, 0.01, and 0.05, respectively) was synthesized by using solid state reaction method. The structural properties were characterized by using X-ray diffraction and scanning electron microscopy. Optical properties were investigated by UV-visible spectroscopy. X-ray diffraction patterns indicate that all samples have hexagonal wurtzite structure without any impurity phases. The diffraction intensity increases and the peak position shifts to a lower 2θ angle with Mn concentration. The lattice parameters a and c, the volume of unit cell increase with Mn content indicating that Mn 2+ ions go to Zn 2+ ions in ZnO lattice. The grain size increases with Mn doping while the microstrain and dislocation density decrease. UV-vis spectra of the samples show that undoped ZnO sample has an energy band gap Eg of 3.34 eV. The optical study indicates a red shift in the absorbance spectra and a decrease in the band gap Eg with Mn content. This decrease of band gap may be attributed to the influence of dopant ions. The morphology and grain distribution of ZnO samples were analysed by scanning electron microscopy. The particle sizes are higher in doped samples when compared to the undoped sample and the surface roughness increases with Mn content. The grains are closely, densely packed and pores/voids between the grains increase with Mn content.

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“…Using these measured transmission spectra, Tauc plots were used to estimate the bandgap for the AZO on Borofloat33 samples reported in this chapter. The estimated bandgap values are higher than what literature suggests for undoped ZnO at room temperature [426,427], and it agrees with literature values for heavily doped ZnO [428,429,430]. This difference could be attributed to the degenerate doping of a semiconductor, where doping ZnO with Al widens its optical bandgap due to the occupation of the lower part of the conduction band with dopants, as described by the Burstein-Moss (BM) effect [431] that was presented in section 4.4.…”

Section: Cary Measurementssupporting

confidence: 88%

Progress towards the realization of an optical Far-Field Superlens

Masouleh¹

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<p>Conventional optics suffer from a fundamental resolution limit due to the nature of light. The near-field superlens concept was introduced two decades ago, and its theory for enabling high resolution imaging is well-established now. Initially, this superlens, which has a simple setup, became a hot topic given the proposition of overcoming the diffraction limit. It has been demonstrated that a near-field superlens can reconstruct images using evanescent waves emanating from small objects by means of resonant excitations on the surface of the superlens. A modified version of the superlens named the far-field superlens is theorized to be able to project the near-field subwavelength information to the far-field region. By design, the far-field superlens is a near-field superlens with nanostructures added on top of it. These nanostructures, referred to as diffraction gratings help couple object information available in the evanescent waves to the far-field. Work reported in this thesis is divided to two major sections. The first describes the modelling technique that investigates the performance of a far-field superlens. This section focuses on evaluating the impact of the diffraction gratings geometry and the object size on the far-field superlens performance as well as the resulting far-field pattern. It was shown that a far-field superlens with a nanograting having a duty cycle of 40% to 50% produces the maximum intensity and contrast in the far-field interactions. For periodic rectangular objects, an inverse-trapezoidal nanograting was shown to provide the best contrast and intensity for far-field interactions. The minimal simulation domain to model a symmetric far-field superlens design was determined both in 2D and 3D. This input reduced the required modelling time and resources. Finally, a 3D far-field superlens model was proposed, and the effect of light polarization on the far-field pattern was studied. The second section of this thesis contains the experimental study that explores a new material as a potential candidate for the construction of far-field superlens. The material conventionally used for superlens design is silver, as its plasmonic properties are well-established. However, scaling down silver features to the nanoscale introduces fundamental fabrication challenges. Furthermore, silver oxidizes due to its reactions with sulphur compounds at ambient conditions, which means that operating a silver far-field superlens is only possible in a well-controlled environment. This disagrees with our proposed concept of a low-cost and robust superlens imaging device. On the other hand, highly doped semiconductors are emerging candidates for plasmonic applications due to the possibility of tuning their optical and electrical properties during the fabrication process. While the working principle of a superlens is independent of the plasmonic material of choice, every plasmonic material has a particular range of operating wavelengths. The pros and cons of each plasmonic material are usually identified once used experimentally. In this work, aluminium-doped zinc oxide was the proposed material of choice for the far-field superlens design. The second part of this thesis details the characterization results of the optical, electrical and structural properties of this proposed alternative. Our aluminium-doped zinc oxide samples were highly transparent for large parts of the spectrum. Their carrier concentration was of the order of 10+20 cm-3, and a resistivity of about 10-3 Ω.cm was achieved. The modelled dielectric permittivity for the studied samples showed a cross-over frequency in the near-infrared region, with the highest plasma frequency achieved in this study being 4710 cm-1.</p>

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ZnO wide bandgap semiconductors preparation for optoelectronic devices

Cited by 22 publications

References 16 publications

Effect of tin on bandgap narrowing and optical properties of ZnO–Zn₂SnO₄ electrospun nanofibre composite

Effect of tin on bandgap narrowing and optical properties of ZnO–Zn₂SnO₄ electrospun nanofibre composite

The Effects of Mn Doping on the Structural and Optical Properties of ZnO

Progress towards the realization of an optical Far-Field Superlens

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ZnO wide bandgap semiconductors preparation for optoelectronic devices

Cited by 22 publications

References 16 publications

Effect of tin on bandgap narrowing and optical properties of ZnO–Zn2SnO4 electrospun nanofibre composite

Effect of tin on bandgap narrowing and optical properties of ZnO–Zn2SnO4 electrospun nanofibre composite

The Effects of Mn Doping on the Structural and Optical Properties of ZnO

Progress towards the realization of an optical Far-Field Superlens

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Product

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Effect of tin on bandgap narrowing and optical properties of ZnO–Zn₂SnO₄ electrospun nanofibre composite

Effect of tin on bandgap narrowing and optical properties of ZnO–Zn₂SnO₄ electrospun nanofibre composite