Browsing by Author "Chen, Rong-Sheng"

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Characteristics of ZnO thin films prepared by radio frequency magnetron sputtering
(2008-03-01)
Yang, Ping-Feng
;
Wen, Hua-Chiang
;
Jian, Sheng-Rui
;
Lai, Yi-Shao
;
Wu, Sean
We investigated in this study structural and nanomechanical properties of zinc oxide (ZnO) thin films deposited onto Langasite substrates at 200 degrees C through radio frequency magnetron sputtering with an radio frequency power at 200 W in an O(2)/Ar gas mixture for different deposition time at 1, 2, and 3 h. Surface morphologies and crystalline structural characteristics were examined using X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The deposited film featured a polycrystalline nature, with (100), (002), and (101) peaks of hexagonal zinc oxide at 31.75 degrees, 34.35 degrees, and 36.31 degrees. As the deposition time increased, the ZnO film became predominantly oriented along the c-axis (002) and the surface roughness decreased. Through Berkovich nanoindentation following a continuous stiffness measurement technique, the hardness and Young's modulus of ZnO thin films increased as the deposition time increased, with the best results being obtained for the deposition time of 3 h. In addition, surface acoustic wave properties of ZnO thin films were also presented. (C) 2007 Elsevier Ltd. All rights reserved.
Characterizations of ZnO thin films deposited onto langasite substrates by r.f. magnetron sputtering
(2007)
Yang, Ping-Feng
;
Wen, Hua-Chiang
;
Jian, Sheng-Rui
;
Lail, Yi-Shao
;
Wu, Sean
We investigated in this study structural and nanomechanical properties of zinc oxide (ZnO) thin films deposited onto langasite substrates at 200 degrees C through r.f. magnetron sputtering with an r.f. power at 200 W in an O2/Ar gas mixture for different deposition time at 1, 2, and 3 h. Surface morphologies and crystalline structural characteristics were examined using x-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The deposited film featured a polycrystalline nature, with (100), (002), and (101) peaks of hexagonal ZnO at 31.75 degrees, 34.35 degrees, and 36.31 degrees. As the deposition time increased, the ZnO film became predominantly oriented along the c-axis (002) and the surface roughness decreased. Through Berkovich nanoindentation following a continuous stiffness measurement (CSM) technique, the hardness and Young\'s modulus of the ZnO thin films increased as the deposition time increased, with the best results being obtained for the deposition time of 3 h.
Morphological, structural, and mechanical characterizations of InGaN thin films deposited by MOCVD
(2008-09-08)
Yang, Ping-Feng
;
Jian, Sheng-Rui
;
Lai, Yi-Shao
;
Yang, Chu-Shou
;
Chen, Rong-Sheng
Presented in this study are surface roughness, crystalline structure, and nanomechanical properties of InGaN thin films deposited under various growth temperatures, obtained by means of X-ray diffraction (XRD), atomic force microscopy (AFM), and nanoindentation techniques. The InGaN thin films with different In contents were deposited on sapphire substrates through a metal-organic chemical-vapor deposition (MOCVD) system. Changes in mechanical properties for InGaN thin films are discussed in conjunction with deposition temperature, surface morphology and crystalline structure. The XRD measurements showed that there was no phase separation of In as the In composition went from 25 at.% to 34 at.%. Moreover, both XRD and AFM showed larger grain and surface roughness in In0.25Ga0.75N thin films. Nanoindentation results indicate that hardness and Young's modulus both decreased as the indentation depth increased. The contact stress-strain relationships were also analyzed. (C) 2007 Elsevier B.V. All fights reserved.
Nanoindentation-induced phase transformation of silicon
(2006)
Yang, Ping-Feng
;
Jian, Sheng-Rui
;
Lai, Yi-Shao
;
Chen, Tsan-Hsien
;
Chen, Rong-Sheng
In this study, the deformation behavior of single-crystal Si (100) was examined using nanoindentation, followed by analysis using cross-sectional transmission electron microscopy (XTEM), scanning electron microscopy (SEM), and Raman microspectroscopy. XTEM samples were prepared by focused ion beam (FIB) milling to accurately position the cross-section through the indentations. The deformation via phase transformation was clearly observed with micro-Raman and XTEM, showing the presence of high-pressure crystalline phases Si-Ill and Si-XII following pressure release. The indentation fracture toughness of Si is also discussed.