Browsing by Author "Jian, S. -R."

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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.
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.
The nanoindentation responses of nickel surfaces with different crystal orientations
(2007)
Ju, S. -P.
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Wang, C. -T.
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Chien, C. -H.
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Huang, J. C.
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Jian, S. -R.
Molecular dynamics (MD) simulations are applied to elucidate the anisotropic characteristics in the material responses for crystallographic nickel substrates with (100), (110) and (111) surface orientations during nanoindentation, compensating for the experimental limitation of nanoindentation-particularly for pure nickel substrates of three crystallographic orientations. This study examines several factors under indentation: three-dimensional phases of plastic deformation which correspond to atomic stress distributions, pile-up patterns at maximum indentation depth, and extracted material properties at different crystallographic orientations. The present results reveal that the strain energy of the substrate exerted by the tip is stored by the formation of the homogeneous nucleation, and is dissipated by the dislocation sliding of the {111} plane. The steep variations of the indentation curve from the local peak to the local minimums are affected by the numbers of slip angle of {111} sliding plane. The pile-up patterns of the three nickel substrates prove that the crystalline nickel materials demonstrate the pile-up phenomenon from nanoindentation on the nano-scale. The three crystallographic nickel substrates exhibit differing amounts of pile-up dislocation spreading at different crystallographic orientations. Finally, the effects of surface orientation in material properties of FCC nickel material on the nano-scale are observable through the slip angle numbers of {111} sliding planes which influence hardness values, as well as the cohesive energy of different crystallographic surfaces that indicate Young's modulus.