Browsing by Author "Juang, J. -Y."

Now showing 1 - 9 of 9

Anisotropic ultrafast dynamics in doped Y1-xCaxBa2Cu3O7-delta superconducting thin films
(2008)
Luo, C. W.
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Wu, K. H.
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Lin, J. -Y.
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Uen, T. M.
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Gou, Y. S.
The anisotropic dynamics of photoinduced quasiparticle in the Y1-xCaxBa2Cu3O7-delta (YCBCO) is revealed by using the orientation-resolved femtosecond reflection spectroscopy. This bulk-sensitive spectroscopy, combining with the well-textured (110)- and (100)- YCBCO thin films, serves as an effective probe to quasiparticle relaxation dynamics along different crystallographic orientations. Since the temperature at which the peak of temperature-dependent relaxation time (tau) manifested in the transient reflectance (Delta R/R) measurements is believed to intimately relate to the opening of superconducting gap, the results reported here should shed some light on the issue of the competing order scenarios for over-doped high-T-c superconductors.
Cross-sectional transmission electron microscopy studies for deformation behaviors of AlN thin films under Berkovich nanoindentation
(2010-08-01)
Jian, Sheng-Rui
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Chen, G. -J.
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Chen, H. -G.
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Jang, Jason S. -C.
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Liao, Y. -Y.
This article reports a nanomechanical response study of the contact-induced deformation behavior in AlN thin film by using a combination of nanoindentation and the cross-sectional transmission electron microscopy (XTEM) techniques. AlN thin films are deposited on Si(1 1 1) substrates by using the helicon sputtering system. The hardness and Young's modulus of the AlN thin film are measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM) mode. The obtained values of hardness and Young's modulus are 24.79 +/- 0.33 GPa and 223.92 +/- 5.34 GPa, respectively. XTEM samples are prepared by using focused ion beam (FIB) milling to accurately position the cross-section of the indented area. Although the film's surface was free from fracture, AlN thin film showed evidence of radial crack along the columnar grain boundary underneath the center of Berkovich indentation for an applied load of 100 mN. XTEM results also indicated that the slip bands on {1 1 1} planes and an indentation-induced phase transformation zone of silicon substrate, containing the metastable phases of Si-III and Si-XII, and, the amorphous phases are observed. (C) 2010 Elsevier B.V. All rights reserved.
Effects of post-annealing on the structural and nanomechanical properties of sputter-deposited FePd thin films
(2015-11-05)
Jian, S. -R.
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Chang, H. -W.
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Wang, Y. -W.
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Yeh, H. -H.
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Juang, J. -Y.
The effects of post-annealing on the microstructures, surface morphologies and nanomechanical characteristics of FePd thin films are investigated by means of X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM) and nanoindentation techniques. The FePd thin films were deposited on the glass substrates at room temperature by magnetron sputtering system. Post-annealing was carried out at 500, 600 and 700 degrees C, respectively, resulting in progressive increase of the average grain size and surface roughness of FePd thin films, as well as the improved film crystallinity. XRD results show that FePd thin films are predominantly (111)-oriented, indicating a well-ordered microstructure. The hardness and Young\'s modulus of FePd thin films measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM) option indicated that both mechanical properties are decreased with increasing the annealing temperature. Furthermore, the relationship between the hardness and films grain size appears to follow closely with the Hall-Petch equation. (C) 2015 Elsevier B.V. All rights reserved.
Influence of annealing temperature on the structural, optical and mechanical properties of ALD-derived ZnO thin films
(2011-06-15)
Yen, C. -Y.
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Jian, S. -R.
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Chen, G. -J.
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Lin, C. -M.
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Lee, H. -Y.
ZnO thin films grown on Si(1 1 1) substrates by using atomic layer deposition (ALD) were annealed at the temperatures ranging from 300 to 500 degrees C. The X-ray diffraction (XRD) results show that the annealed ZnO thin films are highly (0 0 2)-oriented, indicating a well ordered microstructure. The film surface examined by the atomic force microscopy (AFM), however, indicated that the roughness increases with increasing annealing temperature. The photoluminescence (PL) spectrum showed that the intensity of UV emission was strongest for films annealed at 500 degrees C. The mechanical properties of the resultant ZnO thin films investigated by nanoindentation reveal that the hardness decreases from 9.2 GPa to 7.2 GPa for films annealed at 300 degrees C and 500 degrees C, respectively. On the other hand, the Young's modulus for the former is 168.6 GPa as compared to a value of 139.5 GPa for the latter. Moreover, the relationship between the hardness and film grain size appear to follow closely with the Hall-Petch equation. (C) 2011 Elsevier B. V. All rights reserved.
Mechanical responses of Mg-based bulk metallic glasses
(2010-10-01)
Jian, S. -R.
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Li, J. -B.
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Chen, K. -W.
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Jang, Jason S. -C.
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Juang, J. -Y.
In this study, the mechanical responses of the bonded interface method derived Mg(58)Cu(28.5)Gd(11)Ag(2.5) bulk metallic glasses (BMG) under the micro-/nano-indentation are investigated. A modified expanding cavity model is developed to analyze the morphological observations of shear band by Vickers indentation. Results indicate that the radius ratio of any two adjacent shear band circles is approximately constant. The ratio of the shear band deformation zone to the contact radius induced by indentation is also a constant, which depends on the constraint factor (the ratio of hardness to yield strength) of the material. The features predicted by the present model are consistent with the results obtained from the indentation experiments, indicating the validity of the expanding cavity model for describing the mechanical behaviors of the BMG materials. The cross-sectional transmission electron microscopy (XTEM) observations reveal that the terraced shear bands are formed on the interface of the bonded Mg-based BMG. The microstructures for the Vickers indentation-induced terraced shear bands are also discussed. (C) 2010 Elsevier Ltd. All rights reserved.
Nanoindentation Study of FePt Thin Films Deposited by Radio Frequency Magnetron Sputtering
(2016-03)
Chiu, Y. -J.
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Shen, C. -Y.
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Jian, S. -R.
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Chang, H. -W.
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Juang, J. -Y.
The microstructural and nanomechanical properties of Fe0.5Pt0.5 (FePt) thin films deposited on the glass substrates by radio frequency magnetron sputtering were investigated. Specifically, this study focused mainly on the effects of post-annealing on the evolvement of film microstructure and its correlation with the associated nano-mechanical properties. The X-ray diffraction (XRD) results indicated the FePt films were largely equiaxed with the average grain size being increased from similar to 27 nm to similar to 105 nm as the annealing temperature was raised from 400 degrees C to 700 degrees C. The associated film hardness and Young\'s modulus, as derived from the nano-indentation measurements, were decreased from 14.4 +/- 6.8 GPa and 194.2 +/- 9.1 GPa to 8.1 +/- 0.2 GPa and 153.8 +/- 6.5 GPa, respectively. The nano-mechanical properties of the present FePt films were well described by the Hall-Petch relation.
Optical properties of nonlinear solid solution GaSe(1-x) S (x) (0 < x a parts per thousand currency signaEuro parts per thousand 0.4) crystals
(2008-10-01)
Ku, S. -A.
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Luo, C. -W.
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Lio, H. -L.
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Wu, K. -H.
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Juang, J. -Y.
Transmission spectra and phase matching conditions for second harmonic generation in GaSe(1-x) S (x) (0 < x a parts per thousand currency signaEuro parts per thousand 0.4) solid solution crystals are experimentally investigated. An algorithm is suggested and dispersion equations are derived that allow the phase matching angles describing best the available experimental data to be estimated as a function of the mixing ratio x.
Optical properties of nonlinear solid solution GaSe1-x S (x) (0 < x a parts per thousand currency signaEuro parts per thousand 0.4) crystals
(2008-10-01)
Ku, S. -A.
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Luo, C. -W.
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Lio, H. -L.
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Wu, K. -H.
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Juang, J. -Y.
Transmission spectra and phase matching conditions for second harmonic generation in GaSe1-x S (x) (0 < x a parts per thousand currency signaEuro parts per thousand 0.4) solid solution crystals are experimentally investigated. An algorithm is suggested and dispersion equations are derived that allow the phase matching angles describing best the available experimental data to be estimated as a function of the mixing ratio x.
Rapid thermal annealing effects on the structural and nanomechanical properties of Ga-doped ZnO thin films
(2013-09-01)
Jian, S. -R.
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Chen, G. -J.
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Wang, S. -K.
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Lin, T. -C.
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Jang, J. S. -C.
In this study, the structural and nanomechanical properties of Ga-doped ZnO (GZO) thin films on glass substrates followed by rapid thermal annealing (RTA) process were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and nanoindentation techniques. The XRD results indicated that the annealed GZO thin films are textured, having a preferential crystallographic orientation along the hexagonal wurtzite (002) axis. Both the grain size and surface roughness of the annealed GZO thin films exhibit an increasing trend after RTA treatment. The hardness and Young's modulus of the annealed GZO thin films were measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM) option. Furthermore, the hardness and Young's modulus were found to increase with increasing grain size when the RTA time was prolonged from 0.5 to 3 min. The deformation behavior is referred to the inverse Hall-Petch effect commonly observed in systems deformed primarily via grain boundary sliding. The suppression of dislocation movement-associated deformation mechanism might be arisen from strong pinning effects introduced by Ga-doping. (C) 2012 Elsevier B.V. All rights reserved.