Browsing by Author "Wu, Shyh-Chi"

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Effect of repetition nanoindentation of GaN epilayers on a-axis sapphire substrates
(2011-05-01)
Lin, Meng-Hung
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Wen, Hua-Chiang
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Chang, Zue-Chin
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Wu, Shyh-Chi
;
Wu, Wen-Fa
In this work, gallium nitride (GaN) epilayers were deposited on a-axis sapphire substrate by means of metal organic chemical vapor deposition (MOCVD). Berkovich nanoindentation was used to explore the repetition pressure-induced impairment of the GaN film. The observation of load-displacement vs stress-strain curves concludes that basal slip is implicated in the deformation on the A plane GaN. The increase in the hardness (H) and elasticmodulus (E) was determined from cyclic nanoindentation, and resulted in a crack due to the formation of incipient slip bands and/or the to-and-fro motion of mobile dislocation. It is indicated that the generation of individual dislocation and residual deformation of the GaN films are showed by CL mapping analysis. From the morphological studies, it is revealed that the crack was found by means of atomic force microscope (AFM) technique at nine loading/reloading cycles even after the indentation beyond the critical depth on the residual indentation impression. Copyright (C) 2010 John Wiley & Sons, Ltd.
Evaluating nanotribological behavior of annealing Si(0.8)Ge(0.2)/Si films
(2011-12-01)
Wu, Ming-Jhang
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Wen, Hua-Chiang
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Wu, Shyh-Chi
;
Yang, Ping-Feng
;
Lai, Yi-Shao
In this study, the SiGe epilayers were created on silicon substrate by using ultra-high vacuum chemical vapor deposition (UHV/CVD) and followed by annealing procedures. The frictional behaviors of SiGe epilayers were subjected to nanoscratch techniques under a ramping load. Damage caused by scratching was examined by atomic force microscopy (AFM); the results showed that the pile-up phenomena were significant on both sides of the scratch in the case of SiGe epilayers, suggesting that the dynamic deformation behavior was dominated by cracking as ploughing occurred during scratching. In addition, the SiGe epilayers films with different annealed conditions exhibited the decrease in coefficient of friction (COF), indicating the higher shear resistance exist in annealed SiGe epilayers, which probably affect the film uniformity and device yield under IC process integration. (C) 2011 Elsevier Ltd. All rights reserved.
Evaluating nanotribological behavior of annealing Si0.8Ge0.2/Si films
(2011-12-01)
Wu, Ming-Jhang
;
Wen, Hua-Chiang
;
Wu, Shyh-Chi
;
Yang, Ping-Feng
;
Lai, Yi-Shao
In this study, the SiGe epilayers were created on silicon substrate by using ultra-high vacuum chemical vapor deposition (UHV/CVD) and followed by annealing procedures. The frictional behaviors of SiGe epilayers were subjected to nanoscratch techniques under a ramping load. Damage caused by scratching was examined by atomic force microscopy (AFM); the results showed that the pile-up phenomena were significant on both sides of the scratch in the case of SiGe epilayers, suggesting that the dynamic deformation behavior was dominated by cracking as ploughing occurred during scratching. In addition, the SiGe epilayers films with different annealed conditions exhibited the decrease in coefficient of friction (COF), indicating the higher shear resistance exist in annealed SiGe epilayers, which probably affect the film uniformity and device yield under IC process integration. (C) 2011 Elsevier Ltd. All rights reserved.
Fracture responses of microstructures of electron beam-welded D6AC
(2012-07-20)
Wu, Shyh-Chi
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Wen, Hua-Chiang
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Wu, Ming-Jhang
;
Chou, Chang-Pin
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機械工程學系
In this study, D6AC steel was produced from flow forming (wall thickness reduction: 67%) and then it was subjected to electron beam welding and tempering treated. We characterized the specimens in terms of their microstructures and nanotribological properties. After tempering treatment at 315 degrees C, the yield strength increased from 381 to 1334 MPa and the percentage elongation increased remarkably from 0.5 to 7.8%. We performed these mechanical studies for the samples subjected to each set of experimental conditions, and determined the tribological characteristics from the heat-affected zone and the fusion zone. Lower degrees of adhesion reflected the presence of interlinks and rearrangements of indenter tip at lateral force that have been responsible for fluctuations in the coefficients of friction. (C) 2012 Elsevier Ltd. All rights reserved.
Nanoindentation response of zinc titanate thin films deposited by co-sputtering process
(2012-07-01)
Wu, Shyh-Chi
;
Jeng, Yeau-Ren
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Yau, Wei-Hung
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Wu, Kuan-Te
;
Tsai, Chien-Huang
In this study, ZnTiO3 films were grown by radio frequency magnetron co-sputtering using a sintered ceramic target on silicon substrates, we used nanoindenter techniques under a CSM mode to evaluate the hardness (H) and elastic modulus (E) of the films after annealing in temperature range of 520-820 degrees C. The measured values of hardness and elastic moduli of the ZnTiO3 films were in the range from 8.5 +/- 0.4 to 5.6 +/- 0.4 GPa and from 171 +/- 2.3 to 155 +/- 2.5 GPa, respectively. It is evident that an increase in the roughness due to high annealing temperature using atomic force microscopy. The XRD patterns were observed that as-deposited films are mainly amorphous, however, the hexagonal ZnTiO3 phase was observed with the ZnTiO3 (1 0 4), (1 1 0), (1 1 6), and (2 1 4) peaks from 620 to 820 degrees C, indicating that there is highly (1 0 4)-oriented ZnTiO3 on the silicon substrate. The X-ray photoelectron spectroscopy core level analysis of the ZnTiO3 films have been measured for O 1s that can be attributed the weaker bonds and lower resistance at the film based on the higher annealed temperature. The H, M, Rms, and Ra were altered due to the grain growth and recovery to result in a relax crystallinity at ZnTiO3 films. (C) 2012 Elsevier B. V. All rights reserved.
Nanomechanical characteristics of annealed Si/SiGe superlattices
(2011-08-15)
Wu, Ming-Jhang
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Wen, Hua-Chiang
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Wu, Shyh-Chi
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Yang, Ping-Feng
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Lai, Yi-Shao
In this study, the nanomechanical damage was investigated on the annealed Si/SiGe strained-layer superlattices (SLSs) deposited using an ultrahigh-vacuum chemical vapor deposition (UHVCVD). Nanoscratch, nanoindenter, atomic force microscopy (AFM), and transmission electron microscopy (TEM) techniques were used to determine the nanomechanical behavior of the SiGe films. With a constant force applied, greater hardness number and larger coefficients of friction (mu) were observed on the samples that had been annealed at 600 degrees C, suggesting that annealing of the Si/SiGe SLSs can induce greater shear resistance. AFM morphological studies of the Si/SiGe SLSs revealed that pile-up phenomena occurred on both sides of each scratch, with the formation of some pellets and microparticles. The Si/SiGe SLSs that had been subjected to annealing under various conditions exhibited significantly different features in their indentation results. Indeed, the TEM images reveal slight dislocation propagation in the microstructures. Thus, the hardness and elastic modulus can be increased slightly after annealing treatment because the existence of comparatively unstable microstructures. It is suggested that cracking phenomena dominate the damage cause of Si/SiGe SLSs. (C) 2011 Elsevier B. V. All rights reserved.
Nanotribological behavior of thermal treatment of zinc titanate thin films
(2012-10-01)
Wu, Shyh-Chi
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Yau, Wei-Hung
;
Tsai, Chien-Huang
;
Chou, Chang-Pin
;
機械工程學系
We present a study of the nanotribological behavior of ZnTiO3 films; the surface morphology, stoichiometry, and friction (mu) were analyzed using atomic force microscopy, X-ray photoelectron spectroscopy, and nanoscratch system. It is confirmed that the measured values of H and mu of the ZnTiO3 films were in the range from 8.5?+/-?0.4 to 5.6?+/-?0.4 GPa and from 0.164 to 0.226, respectively. It is suggested that the hexagonal ZnTiO3 decomposes into cubic Zn2TiO4 and rutile TiO2 based on the thermal treatment; the H, mu, and RMS were changed owing to the grain growth and recovery that results in a relax crystallinity of ZnTiO3 films. From X-ray photoelectron spectroscopy measured, core levels of O 1 can attribute the weaker bonds as well as lower resistance after thermal treatment. The XRD patterns showed that as-deposited films are mainly amorphous; however, the hexagonal ZnTiO3 phase was observed with the ZnTiO3 (104), (110), (116), and (214) peaks from 620 to 820 degrees C, indicating that there is highly (104)-oriented ZnTiO3 on the silicon substrate. Copyright (c) 2012 John Wiley & Sons, Ltd.
Sliding wear resistance of tempered D6ac steel
(2013-01-01)
Wu, Shyh-Chi
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Wene, Hua-Chiang
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Tseng, Kuang-Hung
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Yau, Wei-Hung
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Wu, Ming-Jhang
The aim of this study was to determine the sliding wear resistance of D6ac (tempered at room temperature, 450, or 550 degrees C) and to perform tribological responds. The obtained microstructures exhibited a heavy number of misfit dislocations from work hardening of the parent material, with the degree of disorder dislocation decreasing gradually upon increasing the temperature from 450 to 550 degrees C. XRD spectra observed that the residual austenite and/or mixed structures of ferrite with the precipitation of carbides at 550 degrees C will result in a softer state than that of the room temperature specimen. The elevated temperature affected the tribological behavior and induced in the parent material a significant surface response failure. The lateral force increased gradually up to 50 mu N in the tempered cases, due to the enhanced toughness. We suggest that the increase in the coefficients of friction upon increasing the tempering temperature from 450 to 550 degrees C resulted due to a soft ferrite phase. Slightly stable fluctuations of the values of mu appeared for the surfaces scratched at a constant load; therefore, plastic deformation occurred along the wear path. For the measured results of the D6ac from room temperature to 550 degrees C, the coefficient of friction was 0.34 +/- 0.05, 0.27 +/- 0.04, and 0.13 +/- 0.02, respectively. The experimental result also can be evidenced from tribological stressing and mechanical behavior. (C) 2012 Elsevier Ltd. All rights reserved.
Tribological behavior of electron beam D6ac weldment
(2013-01-01)
Wu, Shyh-Chi
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Tseng, Kuang-Hung
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Wen, Hua-Chiang
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Wu, Ming-Jhang
;
Chou, Chang-Pin
A flow formed D6ac steel tubing was joined using electron beam (EB) welding. Thereafter, the EB weldments were treated by tempering at temperatures of 450 degrees C and 550 degrees C. After tempering, the microstructural features, mechanical properties, and tribological characteristics of the EB D6ac weldment were studied. This study used a scratch test to evaluate the sliding wear resistance of the tempered weldment. Results indicate that the tempering softens the microstructure by reducing the dislocation density of the flow formed D6ac steel. For the 450 degrees C/2 h/air cooling tempering treated D6ac steel, the fracture toughness of the EB weldment can be significantly improved. The tribological behavior of the tempered D6ac weldment depended on the tempered microstructures. (C) 2012 Elsevier B.V. All rights reserved.