Browsing by Author "Chen, Guo-Ju"

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Annealing-Driven Microstructural Evolution and Its Effects on the Surface and Nanomechanical Properties of Cu-Doped NiO Thin Films
(2019-02-01)
Wang, San-Ho
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Jian, Sheng-Rui
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Chen, Guo-Ju
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Cheng, Huy-Zu
;
Juang, Jenh-Yih
The effects of annealing temperature on the structural, surface morphological and nanomechanical properties of Cu-doped (Cu-10 at %) NiO thin films grown on glass substrates by radio-frequency magnetron sputtering are investigated in this study. The X-ray diffraction (XRD) results indicated that the as-deposited Cu-doped NiO (CNO) thin films predominantly consisted of highly defective (200)-oriented grains, as revealed by the broadened diffraction peaks. Progressively increasing the annealing temperature from 300 to 500 degrees C appeared to drive the films into a more equiaxed polycrystalline structure with enhanced film crystallinity, as manifested by the increased intensities and narrower peak widths of (111), (200) and even (220) diffraction peaks. The changes in the film microstructure appeared to result in significant effects on the surface energy, in particular the wettability of the films as revealed by the X-ray photoelectron spectroscopy and the contact angle of the water droplets on the film surface. The nanoindentation tests further revealed that both the hardness and Young's modulus of the CNO thin films increased with the annealing temperature, suggesting that the strain state and/or grain boundaries may have played a prominent role in determining the film's nanomechanical characterizations.
Nanoindentation-induced phase transformation in (110)-oriented Si single-crystals
(2010-06-01)
Jian, Sheng-Rui
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Chen, Guo-Ju
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Juang, Jenh-Yih
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電子物理學系
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Department of Electrophysics
Pressure-induced plastic deformation and phase transformations manifested as the discontinuities displayed in the loading and unloading segments of the load-displacement curves were investigated by performing the cyclic nanoindentation tests on the (1 1 0)-oriented Si single-crystal with a Berkovich diamond indenter. The resultant phases after indentation were examined by using the cross-sectional transmission electron microscopy (XTEM) technique. The behaviors of the discontinuities displayed on the loading and re-loading segments of the load-displacement curves are found to closely correlate to the formation of Si-II metallic phase, while those exhibiting on the unloading segments are relating to the formation of metastable phases of Si-XII, and amorphous silicon as identified by TEM selected area diffraction (SAD) analyses. Results revealed that the primary indentation-induced deformation mechanism in Si is intimately depending on the detailed stress distributions, especially the reversible Si-II <-> Si-XII/Si-III phase transformations might have further complicated the resultant phase distribution. In addition to the frequently observed stress-induced phase transformations and/or crack formations, evidence of dislocation slip bands was also observed in tests of Berkovich nanoindentation. (C) 2009 Elsevier Ltd. All rights reserved.
Structural and nanomechanical properties of a-plane ZnO thin films deposited under different oxygen partial pressures
(2012-05-01)
Jian, Sheng-Rui
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Chen, Hou-Guang
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Chen, Guo-Ju
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Jang, Jason S. C.
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Juang, Jenh-Yih
The effects of O-2 partial pressure during RF magnetron sputtering on the structural and nanomechanical properties of a-plane ZnO thin films were investigated by using X-ray diffraction (XRD) and nanoindentation techniques. The XRD and the transmission electron microscopy (TEM) selected area diffraction results indicate that the epitaxial relationship between ZnO thin films and Al2O3 substrates is ZnO (11 (2) over bar0)//Al2O3 (1 (1) over bar 02). The average values of the hardness and Young's modulus of the a-plane ZnO films were found to decrease with increasing oxygen partial pressure. The cross-sectional TEM revealing the localized plastic deformation of ZnO thin films beneath the Berkovich indenter, indicating the prominent role played by the threading dislocations in the film deformation behavior. At higher indentation loadings, the sapphire substrate exhibits extensive deformation with narrow slip bands appearing on {0001} plane. However, no evidence of pressure-induced phase transformation, as well as cracking and/or delamination phenomena at the film-substrate interface was observed. (C) 2011 Elsevier B.V. All rights reserved.
Surface Analysis and Optical Properties of Cu-Doped ZnO Thin Films Deposited by Radio Frequency Magnetron Sputtering
(2018-08-01)
Chen, Guo-Ju
;
Jian, Sheng-Rui
;
Juang, Jenh-Yih
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電子物理學系
;
Department of Electrophysics
In this study, Cu-doped ZnO (CZO) thin films were grown on glass substrates by using the radio frequency magnetron sputtering technique. The effects of Cu doping on the structural, surface morphological, optical properties, and wettability behaviors of CZO thin films were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), UV-Visible spectroscopy, and contact angle measurement, respectively. The XRD results indicated that all CZO thin films were textured, having a preferential crystallographic orientation along the hexagonal wurtzite (002) axis. The average transmittance in the visible wavelength region was above 80% for all CZO thin films. The optical band gap of the CZO films decreased from 3.18 to 2.85 eV when the Cu-doping was increased from 2% to 10%. In addition, the water contact angle measurements were carried out to delineate the Cu-doping effects on the changes in the surface energy and wettability of the films.
The effects of annealing temperature and sputtering power on the structure and magnetic properties of the Co-Fe-Zr-B thin films
(2012-11-01)
Chen, Guo-Ju
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Jian, Sheng-Rui
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Jang, Jason Shian-Ching
;
Shih, Yung-Hui
;
Chen, Yuan-Tsung
The microstructure and magnetic properties of the amorphous Co-Fe-Zr-B thin films grown on glass substrates by dc magnetron sputtering are investigated using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) techniques. The Co-Fe-Zr-B thin films deposited at room temperature were annealed at temperatures ranged from 683 K to 773 K. Experimental results indicated that the coercivity (H-c) of the Co-Fe-Zr-B thin films is significantly influenced by residual stress and crystalline phases within the films. The correlation of the coercivity and the microstructure of Co-Fe-Zr-B thin films are discussed. After annealed at 683 K, the coercivity of the Co-Fe-Zr-B film was as low as 1.2 Oe. (C) 2012 Elsevier Ltd. All rights reserved.