Browsing by Author "Lee, Yi-Chia"

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Electroplated Ni-CNT Nanocomposite for Micromechanical Resonator Applications
(2012-06-01)
Lee, Yi-Chia
;
Li, Ming-Huang
;
Cheng, Y. T.
;
Hsu, Wensyang
;
Li, Sheng-Shian
In this letter, electroplated Ni-CNT nanocomposite is synthesized and utilized as a structural material for micromechanical resonator fabrication. Pretreated by sulfate sodium dodecyl, carbon nanotubes (CNTs) disperse well in electrolyte and can be incorporated in an electroplated Ni film. Clamped-clamped beam resonators fabricated using the nanocomposite show similar to 27% resonant frequency enhancement (from 498.75 to 634.72 kHz). Meanwhile, the Q factors of 781 and 760 for Ni and Ni-CNT nanocomposite resonators, which are comparable with the prior art, indicate that the anchor loss could dominate the Q performance of the beam resonators.
ELECTROPLATING PROCESS OF NI-CNTS NANOCOMPOSITE FOR MEMS RESONATOR FABRICATION
(2011)
Lee, Yi-Chia
;
Cheng, Y. T.
;
Hsu, Wensyang
;
機械工程學系
;
Department of Mechanical Engineering
The paper presents an electroplating process for Ni-Carbon Nanotubes (CNTs) nanocomposite micro-resonator (or mu-resonator) fabrication. Two kinds of chemical treatments, H(2)SO(4)/H(2)O(2) and Sodium dodecyl sulfate (SDS) have been utilized for the surface modification of CNTs, respectively. The resonant frequency and Q factor of the SDS treated Ni-CNTs nanocomposite resonators are 30.65 kHz and 221, respectively. The values are higher than that of the one made of pure Ni and the H(2)SO(4)/H(2)O(2) mixture treated Ni-CNTs nanocomposite. They are 29.35 kHz, 190, and 30.35 kHz, 198, respectively. The experimental results indicate a better dispersion treatment on the CNTs in an electroplating bath could result in more incorporated CNTs in the Ni matrix and exhibit better improvement of device performance.
Stress Gradient Modification of the Electroplated Ni-Diamond Nanocomposite for MEMS Fabrication
(2012)
Lee, Yi-Chia
;
Cheng, Yu-Ting
;
Hsu, Wensyang
;
機械工程學系
;
電子工程學系及電子研究所
The paper investigates the formation of stress gradient in electroplated Ni-based nanocomposite films and presents a process scheme to effectively reduce the stress by lowering plating current density. The stress gradient is characterized by measuring the radius of curvature from the surface profile of Ni-based micro-cantilever beams. For the case of the Ni-based films plated with the current density from 15.3 down to 0.8 mA/cm(2), the stress gradient of the films is formed in the range of -7.13 to -3.23 MPa/mu m. According to the cross sectional SEM images, it is found that the Ni-based film plated with 0.8 mA/cm(2) can have a uniformly distributed grain size that can result in a lower stress gradient. By lowering the plating current density from 15.3 to 0.8 mA/cm(2), about 41% and 21% of the stress gradient reduction can be realized in the Ni and Ni-diamond nanocomposite films, respectively, which can be utilized for MEMS resonator fabrication without having structural warpage. Furthermore, experimental results show that the performance of the Ni-diamond nanocomposite resonator can be enhanced in terms of the increase of resonant frequency and quality factor. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.002205jes] All rights reserved.