Browsing by Author "Jang, Jason Shian-Ching"

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Field emission characteristics of carbon nanotubes post-treated with high-density Ar plasma
(2010-01-15)
Wang, Wen-Pin
;
Wen, Hua-Chiang
;
Jian, Sheng-Rui
;
Cheng, Huy-Zu
;
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.
Mechanical properties of InGaN thin films deposited by metal-organic chemical vapor deposition
(2008-06-15)
Jian, Sheng-Rui
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Jang, Jason Shian-Ching
;
Lai, Yi-Shao
;
Yang, Ping-Feng
;
Yang, Chu-Shou
We report in this study characteristics of InGaN thin films developed by metal-organic chemical vapor deposition (MOCVD) at various growth temperatures. The effect of deposition temperatures on microstructures and mechanical properties are examined using X-ray diffraction (XRD), scanning probe microscopy (SPM), and nanoindentation techniques. The XRD analysis shows no evidence of phase separation for InGaN thin films. The SPM micrographs indicate that the films have relatively smooth surfaces. Hardness and Young's modulus of InGaN thin films vary according to the deposition temperature. As the deposition temperature increases from 730 to 790 degrees C, the grain size increases from 28 to 52 nm. Hardness for InGaN thin films dropped from 13.8 to 17.6 GPa in accordance with the increase of the grain size. By fitting experimental data with the Hall-Petch equation, a probable lattice friction stress of 3.48 GPa and Hall-Petch constant of 73.15 GPa nm(1/2) are obtained. (C) 2007 Elsevier B.V. All rights reserved.
Mechanical properties of the hexagonal HoMnO(3) thin films by nanoindentation
(2010-10-22)
Yen, Cheng-Yo
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Jian, Sheng-Rui
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Lai, Yi-Shao
;
Yang, Ping-Feng
;
Liao, Ying-Yen
The structural and nanomechanical characteristics of the hexagonal HoMnO(3) (HMO) thin films are investigated by means of X-ray diffraction (XRD), atomic force microscopy (AFM) and nanoindentation techniques in this study. The HMO thin films were deposited on YSZ(1 1 1) substrates by pulsed laser deposition (PLD). The XRD results reveal only pure (0 0 0 1)-oriented hexagonal HMO reflections without any discernible traces of impurity or secondary phases. Nanoindentation results exhibit discontinuities in the load-displacement curve (so-called multiple "pop-ins" event) during loading, indicating possible involvement of dislocation activities. No discontinuities were observed on unloading segment of the load-displacement curve. Continuous stiffness measurements (CSM) technique was carried out in the nanoindentation tests to determine the hardness and Young's modulus of the hexagonal HMO thin films. The obtained hardness and Young's modulus of the hexagonal HMO thin films are 14.2 +/- 0.7 GPa and 219.2 +/- 10.6 GPa, respectively with the room-temperature fracture toughness being in the order of 0.4 +/- 0.2 MPa m(1/2). (c) 2010 Elsevier B.V. All rights reserved.
Mechanical properties of the hexagonal HoMnO3 thin films by nanoindentation
(2010-10-22)
Yen, Cheng-Yo
;
Jian, Sheng-Rui
;
Lai, Yi-Shao
;
Yang, Ping-Feng
;
Liao, Ying-Yen
The structural and nanomechanical characteristics of the hexagonal HoMnO3 (HMO) thin films are investigated by means of X-ray diffraction (XRD), atomic force microscopy (AFM) and nanoindentation techniques in this study. The HMO thin films were deposited on YSZ(1 1 1) substrates by pulsed laser deposition (PLD). The XRD results reveal only pure (0 0 0 1)-oriented hexagonal HMO reflections without any discernible traces of impurity or secondary phases. Nanoindentation results exhibit discontinuities in the load-displacement curve (so-called multiple "pop-ins" event) during loading, indicating possible involvement of dislocation activities. No discontinuities were observed on unloading segment of the load-displacement curve. Continuous stiffness measurements (CSM) technique was carried out in the nanoindentation tests to determine the hardness and Young's modulus of the hexagonal HMO thin films. The obtained hardness and Young's modulus of the hexagonal HMO thin films are 14.2 +/- 0.7 GPa and 219.2 +/- 10.6 GPa, respectively with the room-temperature fracture toughness being in the order of 0.4 +/- 0.2 MPa m(1/2). (c) 2010 Elsevier B.V. All rights reserved.
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.