Effect of Concentration on the Optical and Solid State Properties of ZnO Thin Films Deposited by Aqueous Chemical Growth (ACG) Method

Mammah, Sylvester Lekoo; Opara, Fidelix Ekeoma; Sigalo, Friday Barikpe; Ezugwu, Sabastine; Ezema, Fabian I.

doi:10.4236/jmp.2012.310187

Cited by 4 publications

(1 citation statement)

References 26 publications

(22 reference statements)

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“…Among TMOs, zinc oxide stands out as the most frequently employed electron transport layer. − ZnO is categorized as an n-type semiconductor due to inherent crystalline defects such as oxygen vacancies and interstitial Zn atoms. It boasts a wide direct band gap (approximately 3.37 V at room temperature) and exhibits the capacity to form thin films with high optical transparency and electronic mobility. − Furthermore, ZnO thin films exhibit a wide range of work functions, spanning from around 3.0 eV to over 5.0 eV. , The low work function values enable favorable alignment with the work function of transparent conductive oxides (TCOs), typically found in the front electrodes of devices (e.g., approximately 4.4 eV for FTO).…”

Section: Introductionmentioning

confidence: 99%

Influence of Grain Boundaries on Nanoscale Charge Transport Properties of Transparent Conductive ZnO-Based Electrodes

Moreira,

dos Santos,

Salomão

et al. 2023

ACS Appl. Electron. Mater.

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The presence of defect states, such as grain boundaries (GBs), can interfere with the charge transport properties of various semiconductor oxides. In this research, electrostatic force microscopy (EFM) and conducting atomic force microscopy (c-AFM) techniques were used to explore the nanoscale surface electrical properties of zinc oxide (ZnO) thin films deposited on a conductive fluorine-doped tin oxide (FTO) substrate. Films like these are often used as anode materials in photovoltaic and other optoelectronic devices. EFM measurements revealed the presence of charge trapping within the grain boundary region, suggesting localized band-bending effects. Furthermore, a current map obtained through c-AFM indicated that the grain regions exhibited higher conductivity, validating the observations made with EFM. By combination of c-AFM and Kelvin probe force microscopy (KPFM), it was possible to obtain experimental confirmation of band bending at grain boundaries. Data extracted from current−voltage (I−V) curves allowed the quantification of local saturation currents of 1.29 and 0.75 nA at the grain and GB. It was also possible to calculate the difference in potential barrier height between grain and GB as 50.40 meV. Urbach energy calculations identified the existence of defect states within the band gap. These defect states shifted the Fermi level toward the conduction band, reducing the local work functions to 3.93 and 3.89 eV for the grain and GB. These findings align with the thermionic emission (TE) model and Schottky−Mott theory, contributing to a deeper understanding of nanoscale charge transport within ZnO-based anodes and paving the way for the development of transparent conductive oxide-based optoelectronic devices and other applications.

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Section: Introductionmentioning

confidence: 99%

Influence of Grain Boundaries on Nanoscale Charge Transport Properties of Transparent Conductive ZnO-Based Electrodes

Moreira,

dos Santos,

Salomão

et al. 2023

ACS Appl. Electron. Mater.

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Effect of annealing on hydrothermally deposited Co3O4-ZnO thin films for supercapacitor applications

Obodo

Chime

Nkele

et al. 2021

Materials Today: Proceedings

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Properties of nanostructured ZnO thin films synthesized using a modified aqueous chemical growth method

Apeh

Chime

Agbo

et al. 2019

Mater. Res. Express

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Research and development of nano-sized Zinc Oxide (ZnO) has recently received great attention due to its remarkable properties such as large exciton binding energy of 60 meV, extraordinary photosensitivity, nontoxic nature, wide bandgap and the fact that it is a low cost material with many technological applications. The inherent necessity for stoichiometric ZnO nanostructures suggest that a deposition method where the film stoichiometry is controlled by a chemical reaction is unavoidable. Moreover, it is extremely important, when developing new methods for deposition of ZnO nanostructures to keep the deposition system as simple as possible, maximize throughput, and keep costs at a minimum. Modified aqueous chemical growth method offer such an opportunity. In this work, ZnO nano-petals on microscope glass substrates have been prepared by using a modified aqueous chemical growth method. On the other hand, before utilization of the fabricated ZnO nanostructures by any technique for any technological applications, it is essential to investigate morphological, optical, electrical and structural properties. In this work morphological, optical, electrical and structural properties with respect to change in deposition time have been cross examined using FESEM, UV-Vis spectroscopy, I-V properties by Keithley system and XRD respectively. SEM micrographs have revealed very little changes in the shape, orientations and distribution of ZnO nanopetals formed with change in deposition times. SEM micrographs have also revealed the growth pattern for the prepared ZnO nano-petals which proceeds via a nucleation, and coalescence of ZnO nuclei. XRD analysis have revealed that the synthesized ZnO nano-petals have a hexagonal Wurtzite ZnO structure with peaks at 2θ positions 31.7°, 34.4°, 36.2°, 47.4°, 56.5°and 62.7° belonging to the (100), (002), (101), (102), (110) and (103) planes respectively. UV-Vis spectroscopy has in the same way shown that the synthesized ZnO nano-petals have energy band gaps ranging from 3.46 eV to 3.65 eV. I-V measurements have disclosed that the ZnO nano-petals are conductive. Film resistivity values obtained from the I-V curves showed an exponential increase in resistivity with increased film thickness. Our method of preparation of ZnO nano-petals via a chemical assisted route can serve as benchmark for controlled synthesis of ZnO nanostructures for various technological applications.

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Effect of Concentration on the Optical and Solid State Properties of ZnO Thin Films Deposited by Aqueous Chemical Growth (ACG) Method

Cited by 4 publications

References 26 publications

Influence of Grain Boundaries on Nanoscale Charge Transport Properties of Transparent Conductive ZnO-Based Electrodes

Influence of Grain Boundaries on Nanoscale Charge Transport Properties of Transparent Conductive ZnO-Based Electrodes

Effect of annealing on hydrothermally deposited Co3O4-ZnO thin films for supercapacitor applications

Properties of nanostructured ZnO thin films synthesized using a modified aqueous chemical growth method

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