Browsing by Author "Cheng, Huy-Zu"

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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.
Field emission characteristics of carbon nanotubes post-treated with high-density Ar plasma
(2010-01-15)
Wang, Wen-Pin
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Wen, Hua-Chiang
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Jian, Sheng-Rui
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Cheng, Huy-Zu
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Jang, Jason Shian-Ching
The field emission characteristics of carbon nanotubes (CNTs) grown by thermal chemical vapor deposition (CVD) and subsequently surface treated by high-density Ar plasma in an inductively coupled plasma reactive ion etching (ICP-RIE) with the various plasma powers were measured. Results indicate that, after treated by Ar plasma with power between 250 and 500 W, the emission current density of the CNTs is enhanced by nearly two orders of magnitude (increased from 0.65 to 48 mA/cm(2)) as compared to that of the as-grown ones. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to investigate the structural features relevant to the modified field emission properties of CNTs. The SEM images of CNTs subjected to a 500 W Ar plasma treatment exhibit obvious damages to the CNTs. Nevertheless, the turn-on fields decreased from 3.6 to 2.2V/mu m, indicating a remarkable field emission enhancement. Our results further suggest that the primary effect of Ar plasma treatment might be to modify the geometrical structures of the local emission region in CNTs. In any case, the Ar plasma treatment appears to be an efficient method to enhance the site density for electron emission and, hence markedly improving the electric characteristics of the CNTs. (C) 2009 Elsevier B.V. All rights reserved.