Browsing by Author "Tseng, Yu-Chin"

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Dislocation Energetics and Pop-Ins in AlN Thin Films by Berkovich Nanoindentation
(2013-09-01)
Jian, Sheng-Rui
;
Tseng, Yu-Chin
;
Teng, I-Ju
;
Juang, Jenh-Yih
;
電子物理學系
Nanoindentation-induced multiple pop-ins were observed in the load-displacement curves when the mechanical responses of AlN films grown on c-plane sapphire substrates were investigated by using Berkovich indenters. No evidence of phase transformation is revealed by cross-sectional transmission electron microscopy (XTEM) and selected area diffraction (SAD) analyses. Instead XTEM observations suggest that these "instabilities" resulted from the sudden nucleation of dislocations propagating along the slip systems lying on the {0001} basal planes and the {10 (1) over bar1} pyramidal planes commonly observed in hexagonal compound semiconductors. Based on this scenario, an energetic estimation of dislocation nucleation is made.
Nanomechanical properties of Bi2Te3 thin films by nanoindentation
(2015-01-15)
Tasi, Cheng-Hsun
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Tseng, Yu-Chin
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Jian, Sheng-Rui
;
Liao, Ying-Yen
;
Lin, Chih-Ming
In this study, the microstructural, morphological and nanomechanical properties of Bi2Te3 thin films are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and nanoindentation techniques. The Bi2Te3 thin films were deposited on c-plane sapphire substrates using pulsed laser deposition (PLD) under the various helium gas pressures. The XRD results indicated that the Bi2Te3 thin films are textured with the c-axis preferentially oriented normal to the films surface. Both the grain size and surface roughness of the Bi2Te3 thin films exhibit an increasing trend with increasing the helium gas pressure. Furthermore, the hardness and Young\'s modulus of the Bi2Te3 thin films are measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM) mode were found to range from 2.92 +/- 0.12 to 4.02 +/- 0.14 GPa and from 106.31 +/- 0.63 to 127.46 +/- 9.21 GPa, respectively, when the helium gas pressure was increased from 2 x 10(-5) to 2 x 10(-3) Torr. (C) 2014 Elsevier B.V. All rights reserved.
Structural and nanomechanical properties of BiFeO3 thin films deposited by radio frequency magnetron sputtering
(2013-06-25)
Jian, Sheng-Rui
;
Chang, Huang-Wei
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Tseng, Yu-Chin
;
Chen, Ping-Han
;
Juang, Jenh-Yih
The nanomechanical properties of BiFeO3 (BFO) thin films are subjected to nanoindentation evaluation. BFO thin films are grown on the Pt/Ti/SiO2/Si substrates by using radio frequency magnetron sputtering with various deposition temperatures. The structure was analyzed by X-ray diffraction, and the results confirmed the presence of BFO phases. Atomic force microscopy revealed that the average film surface roughness increased with increasing of the deposition temperature. A Berkovich nanoindenter operated with the continuous contact stiffness measurement option indicated that the hardness decreases from 10.6 to 6.8 GPa for films deposited at 350A degrees C and 450A degrees C, respectively. In contrast, Young's modulus for the former is 170.8 GPa as compared to a value of 131.4 GPa for the latter. The relationship between the hardness and film grain size appears to follow closely with the Hall-Petch equation.
The deformation behavior and fracture toughness of single crystal YSZ(111) by indentation
(2018-02-25)
Yen, Cheng-Yo
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Jian, Sheng-Rui
;
Tseng, Yu-Chin
;
Juang, Jenh-Yih
;
電子物理學系
The nano-scale deformation behaviors and indentation-induced fracture features of the (111)-oriented yttrium-stabilized zirconia single crystal (YSZ(111)) were investigated by Berkovich and micro-Vicker indentations, respectively. The load-displacement curves in the Berkovich nano-indentation experiments evidently exhibited indentation-induced single "pop-in" phenomenon during loading, indicating that the nano-scale deformation in the YSZ(111) crystals is due primarily to the activities of dislocation nucleation and propagation. Based on this scenario, the number of nanoindentation-induced dislocation loops giving rise to the pop-in event was estimated to be around 2 x 10(5) with a critical radius of similar to 2 nm. The hardness and Young's modulus of YSZ(111) single crystal obtained by the continuous contact stiffness measurements (CSM) mode were 22.3 +/- 1.1 GPa and 270.6 +/- 8.5 GPa, consistent with those reported previously in the literature. In addition, the fracture toughness of YSZ(111) single crystal was estimated to be about 1.4-1.6 MPa m(1/2). (C) 2017 Elsevier B.V. All rights reserved.