Browsing by Author "Chang, Huang-Wei"

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Influence of Post-Annealing on the Structural and Nanomechanical Properties of Co Thin Films
(2020-02-01)
Hwang, Yeong-Maw
;
Pan, Cheng-Tang
;
Lu, Ying-Xu
;
Jian, Sheng-Rui
;
Chang, Huang-Wei
The correlations between the microstructure and nanomechanical properties of a series of thermal annealed Co thin films were investigated. The Co thin films were deposited on glass substrates using a magnetron sputtering system at ambient conditions followed by subsequent annealing conducted at various temperatures ranging from 300 degrees C to 800 degrees C. The XRD results indicated that for annealing temperature in the ranged from 300 degrees C to 500 degrees C, the Co thin films were of single hexagonal close-packed (hcp) phase. Nevertheless, the coexistence of hcp-Co (002) and face-centered cubic (fcc-Co (111)) phases was evidently observed for films annealed at 600 degrees C. Further increasing the annealing temperature to 700 degrees C and 800 degrees C, the films evidently turned into fcc-Co (111). Moreover, significant variations in the hardness and Young's modulus are observed by continuous stiffness nanoindentation measurement for films annealed at different temperatures. The correlations between structures and properties are discussed.
Structural and nanomechanical properties of BiFeO3 thin films deposited by radio frequency magnetron sputtering
(2013-06-25)
Jian, Sheng-Rui
;
Chang, Huang-Wei
;
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.