Bandgap energy tuning of electrochemically grown ZnO thin films by thickness and electrodeposition potential

Marotti, Ricardo E.

doi:10.1016/j.solmat.2004.01.008

Cited by 209 publications

(67 citation statements)

References 40 publications

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“…Although the feature due to Au electrode is still present, a more clear and typical absorption edge, due to ZnO, appears near 380 nm [15]. The derivative of the spectrum dR/dλ displays a clear peak that indicates a direct semiconductor band edge [28,29], as expected for ZnO [15]. The bandgap energy value obtained from this peak position is 3.29 eV, also in agreement with usually reported values for ZnO [4,27].…”

Section: Chemical Composition and Microstructuresupporting

confidence: 88%

“…Figure 3c shows the corresponding spectrum for ZnO NW arrays. Although the feature due to Au electrode is still present, a more clear and typical absorption edge, due to ZnO, appears near 380 nm [15]. The derivative of the spectrum dR/dλ displays a clear peak that indicates a direct semiconductor band edge [28,29], as expected for ZnO [15].…”

Section: Chemical Composition and Microstructurementioning

confidence: 77%

“…The optical properties of the samples were studied by diffuse reflectance spectroscopy rather than transmittance spectroscopy due to the optically opaque Au back contact [15]. A 1000 W electric power Xe lamp (ORIEL 6271) light source was used for this measurement.…”

Section: Sample Characterizationmentioning

confidence: 99%

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Comparative study on the properties of ZnO nanowires and nanocrystalline thin films

Broitman

Bojorge

Elhordoy³

et al. 2012

Surface and Coatings Technology

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The microstructural, morphological, optical and water-adsorption properties of nanocrystalline ZnO thin films and ZnO nanowires were studied and compared. The ZnO thin films were obtained by a sol–gel process, while the ZnO nanowires were electrochemically grown onto a ZnO sol–gel spin-coated seed layer. Thin films and nanowire samples were deposited onto crystalline quartz substrates covered by an Au electrode, able to be used in a quartz crystal microbalance. X-ray diffraction measurements reveal in both cases a typical diffraction pattern of ZnO wurtzite structure. Scanning electron microscopic images of nanowire samples show the presence of nanowires with hexagonal sections, with diameters ranging from 30 to 90 nm. Optical characterization reveals a bandgap energy of 3.29 eV for the nanowires and 3.35 eV for the thin films. A quartz crystal microbalance placed in a vacuum chamber was used to quantify the amount and kinetics of water adsorption onto the samples. Nanowire samples, which have higher surface areas than the thin films, adsorb significantly more water

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Section: Chemical Composition and Microstructuresupporting

confidence: 88%

Section: Chemical Composition and Microstructurementioning

confidence: 77%

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Comparative study on the properties of ZnO nanowires and nanocrystalline thin films

Broitman

Bojorge

Elhordoy³

et al. 2012

Surface and Coatings Technology

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“…Qin Guoqiang et al [38] have reported that the band gap of wurtzite ZnO changes under triaxial strains, a new type of strain where band gap increases [39] along with a and c lat− tice constants, although ZnO still remains a direct band gap semiconductor. Comparing with the unstrained ZnO, the E g increases under compressive strain but decreases under ten− sile strain.…”

Section: Transmission and Optical Band Gapmentioning

confidence: 99%

Enhancement in UV emission and band gap by Fe doping in ZnO thin films

Srivastava

Kumar

Khare

2014

Opto-Electronics Review

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Enhancement of the optical band gap of ZnO from 3.14 to 3.29 eV has been obtained using Fe dopant. Undoped and doped ZnO films are deposited by sol-gel spin coating. XRD patterns indicate polycrystalline nature and hexagonal wurtzite structure of Zn1−xFexO films. EDX analysis confirms the presence of iron dopant. The photoluminescence spectra show an ultraviolet emission peak at 398 nm (NBE emission) and defect emission peak at 485 nm. Intensity of the NBE emission is much higher for the doped samples with its ratio to defect emission intensity highest for 2 at. %doping. The NBE emission shifts to higher energy with increasing dopant concentration in a manner similar to that exhibited by the band gap. Surface morphology has been studied using FESEM.

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“…In effect, the rise in DR spectra (similar to the one in TT) can be assigned to ZnO bandgap absorption edge. 70 Therefore, the corresponding blue-shift as the NR diameter decreases may be related to quantum confinement effects of charge carriers inside these nanostructures. Although the smalls shifts observed in Fig.…”

Section: Optical Properties Of Thementioning

confidence: 99%

The Effect of a Sputtered Al-Doped ZnO Seed Layer on the Morphological, Structural and Optical Properties of Electrochemically Grown ZnO Nanorod Arrays

Campo¹,

Navarrete-Astorga

Pereyra³

et al. 2016

J. Electrochem. Soc.

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The effect of both a RF sputtered Al-doped ZnO (AZO) thin film seed layer onto a FTO/glass substrate and its growth time onto the morphological, structural and optical properties of the resulting electrochemically grown ZnO nanorod arrays (NRAs) have been studied. ZnO NRs grown onto the different AZO seed layers exhibit smaller mean diameter and length than those grown onto a bare FTO/glass substrate, but ZnO NR density presents an opposite behavior, by using an AZO seed layer ZnO nanorod density can be increased by a factor of six. ZnO nanorods are highly crystalline with a wurtzite hexagonal structure and with a preferential growth perpendicular to the substrate. The c-axis of most of the ZnO NRs grown onto an AZO seed layer is aligned within ±6 • from the substrate surface normal. Both NRAs mean length and density increases light scattering, without greatly affecting the spectra shape. The diffuse reflectance intensity is more sensitive to NR density variations than to length or diameter variations. NR diameter affects directly the shape of these diffuse reflectance spectra: they red-shifts and broadens when NR mean diameter increases. A small influence in the UV edge due to size quantization may be also present. In recent years, ZnO, a wide bandgap semiconductor with a direct bandgap of about 3.37 eV and high exciton binding energy (60 meV) at room temperature, has attracted increasing interest due to its unique ability to form a variety of nanostructures such as nanowires, nanorods, nanobelts, nanocombs, nanospheres, nano-tetrapods.1,2 Among them, the most interesting are nanorods and nanorod arrays (NRAs) vertically arranged with respect to the substrate.1 These ZnO nanostructures present a pseudo-one dimensional (1D) structure, with an enhanced surface-to-volume ratio and confinement effects.3 ZnO nanorods exhibit fewer defects than its thin-film structure, it is, therefore, a promising material for optoelectronic applications. 4 In fact, recently, single crystal ZnO nanowire and nanorod arrays have emerged as promising building blocks for a new generation of devices in different hi-tech domains such as optoelectronics, gas sensing, field emission, piezoelectrics and solar cells. 2,5,6 In particular, ZnO one dimensional nanostructures are good candidates for photovoltaic applications for three straightforward reasons: i) they have a low reflectivity that enhances the light absorption; ii) relatively high surface to volume ratio that enables interfacial charge separation and iii) fast electron transport along the crystalline 1D nanostructures that improves the charge collection efficiency. In fact, ZnO arrays of 1D nanostructures, such as nanowires and nanotubes, have been widely utilized as they provide a direct conduction pathway for the rapid collection of the photogenerated electrons, 7 reducing the non-radiative recombination and carrier scattering loss dramatically, 8 and providing as well a high junction area.9,10 Moreover, electron transport in the crystalline nanorod is expected to be several orde...

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Bandgap energy tuning of electrochemically grown ZnO thin films by thickness and electrodeposition potential

Cited by 209 publications

References 40 publications

Comparative study on the properties of ZnO nanowires and nanocrystalline thin films

Comparative study on the properties of ZnO nanowires and nanocrystalline thin films

Enhancement in UV emission and band gap by Fe doping in ZnO thin films

The Effect of a Sputtered Al-Doped ZnO Seed Layer on the Morphological, Structural and Optical Properties of Electrochemically Grown ZnO Nanorod Arrays

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