Browsing by Author "Lee, Tzong-Ming"

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Effects of Mechanical Strains on the Characteristics of Top-Gate Staggered a-IGZO Thin-Film Transistors Fabricated on Polyimide-Based Nanocomposite Substrates
(2012-07-01)
Lin, Chang-Yu
;
Chien, Chih-Wei
;
Wu, Chung-Chih
;
Yeh, Yung-Hui
;
Cheng, Chun-Cheng
In this paper, we had successfully implemented flexible top-gate staggered amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) on colorless and transparent polyimide (PI)-based nanocomposite substrates using fully lithographic and etching processes that are compatible with existing TFT mass fabrication technologies. The use of the selectively coated release layer between the nanocomposite PI film and the glass carrier ensured smooth debonding of the plastic substrate after TFT fabrication. The TFTs showed decent performances (with mobility > 10 cm(2)/V . s) either as fabricated or as debonded from the carrier glass. By bending the devices to different radii of curvature (from a flat state to an outward bending radius of 5 mm), influences of mechanical strains on the characteristics of flexible a-IGZO TFTs were also investigated. In general, the mobility of the flexible a-IGZO TFT increased with the tensile strain, whereas the threshold voltage decreased with the tensile strain. The variation of the mobility in a-IGZO TFTs versus the strain appeared smaller than those observed for amorphous silicon TFTs.
Thermal conductivity and structure of non-covalent functionalized graphene/epoxy composites
(2011-12-01)
Teng, Chih-Chun
;
Ma, Chen-Chi M.
;
Lu, Chu-Hua
;
Yang, Shin-Yi
;
Lee, Shie-Heng
Non-covalent functionalization was used to functionalize graphene nanosheets (GNSs) through pi-pi stacking of pyrene molecules with a functional segmented polymer chain, which results in a remarkable improvement in the thermal conductivity of GNS-filled polymer composites. The functional segmented poly(glycidyl methacrylate) containing localized pyrene groups (Py-PGMA) was prepared by atom transfer radical polymerization, and Py-PGMA was characterized by nuclear magnetic resonance spectroscopy. Raman spectra, X-ray photoelectron spectroscopy and thermogravimetric analysis reveal the characteristics of Py-PGMA-GNS. Differential scanning calorimetry indicated that the functional groups on Py-PGMA-GNSs can generate covalent bonds with the epoxy matrix, and further form a cross-linked structure in Py-PGMA-GNS/epoxy composites. The Py-PGMA on the GNS surface not only plays an important role to facilitate a homogeneous dispersion in the polymer matrix but also improves the GNS-polymer interaction, which results in a high contact area. Consequently, the thermal conductivity of integrated Py-PGMA-GNS/epoxy composites exhibited a remarkable improvement and is much higher than epoxy reinforced by multi-walled carbon nanotubes or GNSs. The thermal conductivity of 4 phr Py-PGMA-GNS/epoxy has about 20% (higher than that of pristine GNS/epoxy) and 267% (higher than pristine MWCNT/epoxy). (C) 2011 Elsevier Ltd. All rights reserved.