Structural and optical properties of ZnO thin films prepared by molecular precursor and sol–gel methods

Theopolina Amakali; Likius S. Daniel; Veikko Uahengo; Nelson Y. Dzade; Nora H. de Leeuw

doi:10.3390/cryst10020132

Structural and optical properties of ZnO thin films prepared by molecular precursor and sol–gel methods

Theopolina Amakali^*, Likius S. Daniel, Veikko Uahengo, Nelson Y. Dzade, Nora H. de Leeuw

^*Corresponding author for this work

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

Zinc oxide (ZnO) is a versatile and inexpensive semiconductor with a wide direct band gap that has applicability in several scientific and technological fields. In this work, we report the synthesis of ZnO thin films via two simple and low-cost synthesis routes, i.e., the molecular precursor method (MPM) and the sol–gel method, which were deposited successfully on microscope glass substrates. The films were characterized for their structural and optical properties. X-ray diffraction (XRD) characterization showed that the ZnO films were highly c-axis (0 0 2) oriented, which is of interest for piezoelectric applications. The surface roughness derived from atomic force microscopy (AFM) analysis indicates that films prepared via MPM were relatively rough with an average roughness (Ra) of 2.73 nm compared to those prepared via the sol–gel method (Ra = 1.55 nm). Thin films prepared via MPM were more transparent than those prepared via the sol–gel method. The optical band gap of ZnO thin films obtained via the sol–gel method was 3.25 eV, which falls within the range found by other authors. However, there was a broadening of the optical band gap (3.75 eV) in thin films derived from MPM.

Original language	English
Article number	132
Number of pages	11
Journal	Crystals
Volume	10
Issue number	2
DOIs	https://doi.org/10.3390/cryst10020132
Publication status	Published - 22 Feb 2020

Funding

Funding: The authors acknowledge the Royal Society and the UK Department for International Development, for a research grant under the Africa Capacity Building Initiative (ACBI), which funded this research. Acknowledgments: This work made use of XRD and AFM facilities of the Botswana International University of Acknowledgments: This work made use of XRD and AFM facilities of the Botswana International University of Science and Technology (BIUST) and we are grateful to Foster Mbaiwa for his help with sample characterization. Sachin Rondiya is thanked for his assistance with the analyses of the XRD and AFM data. The SEM instrument uscehdariascbtearsiezdataitonSw. Danr.s SeaacUhinni vReorsnidtyiyaan ids DthaannikeledR .fJoornheiss iassaspisptarenccieatwedithfotrhheisanhaellypswesitohf SthEeM XmRDeaasundre mAFenMts d. ata. The SEM instrument used is based at Swansea University and Dr Daniel R. Jones is appreciated for his help with SEM measurements.

Keywords

Crystallite size
Molecular precursor method
Optical band gap
Zinc oxide

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title = "Structural and optical properties of ZnO thin films prepared by molecular precursor and sol–gel methods",

abstract = "Zinc oxide (ZnO) is a versatile and inexpensive semiconductor with a wide direct band gap that has applicability in several scientific and technological fields. In this work, we report the synthesis of ZnO thin films via two simple and low-cost synthesis routes, i.e., the molecular precursor method (MPM) and the sol–gel method, which were deposited successfully on microscope glass substrates. The films were characterized for their structural and optical properties. X-ray diffraction (XRD) characterization showed that the ZnO films were highly c-axis (0 0 2) oriented, which is of interest for piezoelectric applications. The surface roughness derived from atomic force microscopy (AFM) analysis indicates that films prepared via MPM were relatively rough with an average roughness (Ra) of 2.73 nm compared to those prepared via the sol–gel method (Ra = 1.55 nm). Thin films prepared via MPM were more transparent than those prepared via the sol–gel method. The optical band gap of ZnO thin films obtained via the sol–gel method was 3.25 eV, which falls within the range found by other authors. However, there was a broadening of the optical band gap (3.75 eV) in thin films derived from MPM.",

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AU - Uahengo, Veikko

AU - Dzade, Nelson Y.

AU - de Leeuw, Nora H.

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AB - Zinc oxide (ZnO) is a versatile and inexpensive semiconductor with a wide direct band gap that has applicability in several scientific and technological fields. In this work, we report the synthesis of ZnO thin films via two simple and low-cost synthesis routes, i.e., the molecular precursor method (MPM) and the sol–gel method, which were deposited successfully on microscope glass substrates. The films were characterized for their structural and optical properties. X-ray diffraction (XRD) characterization showed that the ZnO films were highly c-axis (0 0 2) oriented, which is of interest for piezoelectric applications. The surface roughness derived from atomic force microscopy (AFM) analysis indicates that films prepared via MPM were relatively rough with an average roughness (Ra) of 2.73 nm compared to those prepared via the sol–gel method (Ra = 1.55 nm). Thin films prepared via MPM were more transparent than those prepared via the sol–gel method. The optical band gap of ZnO thin films obtained via the sol–gel method was 3.25 eV, which falls within the range found by other authors. However, there was a broadening of the optical band gap (3.75 eV) in thin films derived from MPM.

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Structural and optical properties of ZnO thin films prepared by molecular precursor and sol–gel methods

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