Browsing by Author "Hsu, Chih-Yu"

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A Method of Extracting Metal-Gate High-k Material Parameters Featuring Electron Gate Tunneling Current Transition
(2011-04-01)
Hsu, Chih-Yu
;
Chang, Hua-Gang
;
Chen, Ming-Jer
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
For metal-gate high-k dielectrics, there is a transition region in the electron gate tunneling current I(g), as characterized by a plot of dlnI(g)/dV(g) versus V(g). In this paper, we systematically construct a new fitting over the region, which can accurately determine material parameters, including metal work function, high-k electron affinity, and tunneling effective masses of electrons. First of all, a calculation of gate current due to electron direct tunneling and/or Fowler-Nordheim tunneling from an inversion layer is performed, yielding the guidelines of the fitting. Experimental samples are presented with n-channel metal-oxide-semiconductor field-effect transistors having low effective oxide thickness (1.4 nm) TaC/HfSiON/SiON gate stacks. Underlying material parameters are extracted accordingly and remain valid for higher temperature and gate voltage. We also demonstrate that a conventional method without a dlnI(g)/dV(g) fitting might lead to erroneous results. Thus, the dlnI(g)/dV(g) fitting is crucial to metal-gate high-k material parameter assessment.
Dual-color electrochromic films incorporating a periodic polymer nanostructure
(2012)
Wei, Hung-Yu
;
Hsiao, Yu-Sheng
;
Huang, Jen-Hsien
;
Hsu, Chih-Yu
;
Chang, Feng-Chih
In this study, we used electrochemical deposition with a polystyrene (PS) bead template to prepare thin layers of poly(3,4-ethylenedioxythiophene) (PEDOT) that has a nanometer-scale honeycomb periodicity. To achieve dual-color electrochromic films, we then used pulsed electrochemical deposition to form polyaniline (PANI) layers on the rims of the PEDOT honeycomb film. Modifying the depositing charge density of PANI allowed tuning of the color of the composite films. We estimated the coloration efficiencies with respect to the values expected for corresponding amounts of pristine single layers of PEDOT and PANI. As a result of improved contact between the polymer film and the electrolyte, the coloration efficiencies of the structured composite films were much closer to their theoretical values than those of the corresponding bilayer composite films. Moreover, the switching times of the structured composite films were much faster than those of the bilayer composite films prepared without the nanostructures.
Dye-sensitized solar cells with a micro-porous TiO(2) electrode and gel polymer electrolytes prepared by in situ cross-link reaction
(2009-11-01)
Lee, Kun-Mu
;
Hsu, Chih-Yu
;
Chiu, Wei-Hao
;
Tsui, Meng-Chin
;
Tung, Yung-Liang
The ionic conductivities and performances of dye-sensitized solar cells(DSSCs) of gel polymer electrolytes(GPEs) prepared by in situ cross-link reaction with different cross-linkers were investigated. The poly(imidazole-co-butylmethacrylate)-based GPE containing the 1,2,4,5-tetrakis(bromomethyl)benzene (B4Br) cross-linker showed a higher ionic conductivity than that containing cross-linkers with a linear structure, due to the formation of micro-phase separation that resulted in an increase in ion transport paths in the GPE. Moreover, the co-adsorbent((4-pyridylthio) acetic acid, PAA) co-adsorbed with N3 dye on the TiO(2) electrode not only reduced dye aggregation, but also reacted with the cross linkers in the GPE at the TiO(2)/GPE interface. A decrease in the charge transport resistance at the TiO2/GPE interface was noted after forming the gel; thus the value of J(SC) significantly increased from 7.72 to 10.00 m A cm(-2). In addition, in order to reduce the ionic diffusion resistance within the TiO(2) electrode, incorporation of monodispersed PMMA in the TiO(2) paste was considered. With the optimal weight ratio of PMMA/TiO(2) (w/w 3.75), the TiO(2) electrode exhibited larger pores (ca. 350 nm) uniformly distributed afters intering at 500 degrees C, and the ionic diffusion resistance within the TiO2 film could significantly be reduced. The cell conversion efficiency increased from 3.61% to 5.81% under illumination of 100 mW cm (-2), an improvement of ca. 55%. (C) 2009 Elsevier B. V. All rights reserved.
Dye-sensitized solar cells with a micro-porous TiO2 electrode and gel polymer electrolytes prepared by in situ cross-link reaction
(2009-11-01)
Lee, Kun-Mu
;
Hsu, Chih-Yu
;
Chiu, Wei-Hao
;
Tsui, Meng-Chin
;
Tung, Yung-Liang
The ionic conductivities and performances of dye-sensitized solar cells(DSSCs) of gel polymer electrolytes(GPEs) prepared by in situ cross-link reaction with different cross-linkers were investigated. The poly(imidazole-co-butylmethacrylate)-based GPE containing the 1,2,4,5-tetrakis(bromomethyl)benzene (B4Br) cross-linker showed a higher ionic conductivity than that containing cross-linkers with a linear structure, due to the formation of micro-phase separation that resulted in an increase in ion transport paths in the GPE. Moreover, the co-adsorbent((4-pyridylthio) acetic acid, PAA) co-adsorbed with N3 dye on the TiO2 electrode not only reduced dye aggregation, but also reacted with the cross linkers in the GPE at the TiO2/GPE interface. A decrease in the charge transport resistance at the TiO2/GPE interface was noted after forming the gel; thus the value of J(SC) significantly increased from 7.72 to 10.00 m A cm(-2). In addition, in order to reduce the ionic diffusion resistance within the TiO2 electrode, incorporation of monodispersed PMMA in the TiO2 paste was considered. With the optimal weight ratio of PMMA/TiO2 (w/w 3.75), the TiO2 electrode exhibited larger pores (ca. 350 nm) uniformly distributed afters intering at 500 degrees C, and the ionic diffusion resistance within the TiO2 film could significantly be reduced. The cell conversion efficiency increased from 3.61% to 5.81% under illumination of 100 mW cm (-2), an improvement of ca. 55%. (C) 2009 Elsevier B. V. All rights reserved.
Enhanced Hole Gate Direct Tunneling Current in Process-Induced Uniaxial Compressive Stress p-MOSFETs
(2009-08-01)
Hsu, Chih-Yu
;
Lee, Chien-Chih
;
Lin, Yi-Tang
;
Hsieh, Chen-Yu
;
Chen, Ming-Jer
On a nominally 1.27-nm-thick gate oxide p-MOSFET with shallow trench isolation (STI) longitudinal compressive mechanical stress, hole gate direct tunneling current in inversion is measured across the wafer. The resulting average gate current exhibits an increasing trend with STI compressive stress. However, this is exactly contrary to the currently recognized trend: hole gate direct tunneling current decreases with externally applied compressive stress, which is due to the strain-altered valence-band splitting. To determine the mechanisms responsible, a quantum strain simulator is established, and its validity is confirmed. The simulator then systematically leads us to the finding of the origin: a reduction in the physical gate oxide thickness, with the accuracy identified down to 0.001 nm, occurs under the influence of the STI compressive stress. The strain-retarded oxide growth rate can significantly enhance hole direct tunneling and thereby reverse the conventional trend due to the strain-altered valence-band splitting.
Evidence for a Very Small Tunneling Effective Mass (0.03m(0)) in MOSFET High-k (HfSiON) Gate Dielectrics
(2012-04-01)
Chen, Ming-Jer
;
Hsu, Chih-Yu
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have recently conducted experimental and modeling tasks on TaC/HfSiON/SiON n-type MOSFETs, leading to an effective mass of 0.03m(0) for 2-D electrons tunneling in high-k HfSiON dielectrics. In this letter, we present extra evidence obtained from complementary MOSFETs undergoing the same TaC/HfSiON/SiON processing, which shows that such a very small tunneling effective mass is existent not only for 3-D electrons but also for 2-D holes. This new finding is very important because it can substantially enhance the current understanding of gate tunneling leakage suppression in metal-gate high-k MOSFETs.
INCORPORATING TEXTURE INFORMATION INTO REGION-BASED UNSUPERVISED IMAGE SEGMENTATION USING TEXTURAL SUPERPIXELS
(2014)
Hsu, Chih-Yu
;
Hsieh, Yi-Yu
;
Lo, Kuo-Hua
;
Chuang, Jen-Hui
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資訊工程學系
Recently, an unsupervised image segmentation framework, Segmentation by Aggregating Superpixels (SAS) is proposed and shown to be very promising. However, the texture cues, which have been shown to be very effective in many researches, are not used. In this paper, we propose an effective method for incorporating texture information into the SAS framework, using superpixels. To extract texture information, our algorithm first uses texture filtering and subsequently GMM clustering. Then, we develop an edge-aware low-pass filtering to generate multiple-scale textural superpixels (TXSPs) from the clustering results. Finally, by joining TXSPs with the superpixel set originally used in SAS, the incorporation of texture information is accomplished. Our method achieves superior performance on the Berkeley Segmentation Dataset (BSDS300) under several evaluation criteria when compared to other benchmark algorithms.
Influence of molecular weight on silole-containing cyclopentadithiophene polymer and its impact on the electrochromic properties
(2012-03-01)
Huang, Jen-Hsien
;
Huang, Annie Tzuyu
;
Hsu, Chih-Yu
;
Lin, Jiann-Tsuen
;
Chu, Chih-Wei
In this article, we have systematically studied the effect of molecular weight on poly[(4,4'-bis(2-ethylhexyl)dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(5,5'-thienyl-4,4'-dihexyl-2,2'bithiazole)-2,6-diyl], a novel cathodically coloring electrochromic polymer. The polymer with higher molecular weight can stack much better due to the stronger pi-pi* interaction and was found to exhibit better charge transfer property and lower internal resistance. These results have shown to enhance the coloration efficiency of the polymer remarkably. For the molecular weight of 33.6 kg/mol, the coloration efficiency is 423 cm(2)/C, much higher compared with the low molecular weight polymer (6.3 kg/mol, 226 cm(2)/C). (C) 2011 Elsevier B.V. All rights reserved.
On the Mean Free Path for Backscattering in k(B)T Layer of Bulk Nano-MOSFETs
(2008-12-01)
Chen, Ming-Jer
;
Lu, Li-Fang
;
Hsu, Chih-Yu
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We perform Monte Carlo particle simulations on a silicon conductor for the purposes of reexamining the channel backscattering in bulk nano-MOSFETs. The resulting mean free path lambda(0) for backscattering in a long and near-equilibrium conductor is constant, regardless of the potential profile. However, the apparent mean free path lambda(1) in a local quasi-ballistic k(B)T layer depends on the curvature of the potential profile. In a linear potential profile, the lambda(1) extracted in a wide range of the conductor length (15 to 100 nm) and lattice temperature (150 to 300 K) is found to fall below lambda(0). The carrier heating as the origin of reduced mean free path is inferred from the simulated carrier velocity distribution near the injection point. Strikingly, the mean free paths in a parabolic potential profile remain consistent: lambda(1) = lambda(0) This indicates the absence or weakening of the carrier heating in the layer of interest, valid only for the parabolic potential barrier.
Organic solar cells featuring nanobowl structures
(2013-04-01)
Wei, Hung-Yu
;
Huang, Jen-Hsien
;
Hsu, Chih-Yu
;
Chang, Feng-Chih
;
Ho, Kuo-Chuan
Although organic solar cells having a bilayer configuration provide continuous conducting pathways for carrier transport to the requisite electrodes, their efficiencies have remained low because of the short exciton diffusion lengths of organic semiconductors. In this paper, we describe unique spatial organic solar cells featuring nanobowl array structures that capture more light and generate more power than planar organic solar cells. To construct bilayer solar cells, we used electrochemical deposition (with polystyrene beads as the template) to fabricate poly(3,4-ethylenedioxythiophene) nanobowl arrays, functioning as the hole extraction layer, on indium tin oxide substrates and then deposited copper phthalocyanine and a fullerene (C-60 or C-70) to function as the active layer, onto the nanobowl arrays. By implementing this spatial structure, we could control the active layer's thickness, such that it would be suitable for exciton dissociation, while maintaining a high absorption of incident light (by increasing the absorber volume without decreasing the area of the donor-acceptor interface, such that the light path in the active layer was increased) and ensuring high exciton dissociation efficiency (by enlarging the donor-acceptor interface). Relative to an equally thick planar control active layer the photocurrent generated by such bilayer solar cells increased by approximately 90%.
Solvent-Annealing-Induced Self-Organization of Poly(3-hexylthiophene), a High-Performance Electrochromic Material
(2009-12-01)
Huang, Jen-Hsien
;
Yang, Chuan-Yi
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Hsu, Chih-Yu
;
Chen, Cheng-Lun
;
Lin, Lu-Yin
We have systematically studied the self-organization of poly(3-hexylthiophene) (P3HT), an electrochromic material, upon control of the solvent evaporation race. We characterized these polymer films using atomic force microscopy and X-ray diffraction measurements. Well-ordered P3HT structures were developed after solvent annealing; these highly crystalline structures exhibited enhanced electrochromic contrast and reduced resistance within the film, leading to larger coloration efficiencies and faster switching times. The optical contrast (Delta%T), coloration efficiency, and switching time of the P3HT films increased from 54.2%, 182,6 cm(2) C(-1), and 5.3 s, respectively, prior to solvent annealing to 64.8%, 293.5 cm(2) C(-1), and 3.2 s, respectively, after application of the solvent-annealing conditions.
The Influence of Charge Trapping on the Electrochromic Performance of Poly(3,4-alkylenedioxythiophene) Derivatives
(2010-02-01)
Huang, Jen-Hsien
;
Hsu, Chih-Yu
;
Hu, Chih-Wei
;
Chu, Chih-Wei
;
Ho, Kuo-Chuan
This paper describes the electrochromic properties of a series of poly(3,4-alkylenedioxythiophene) (PXDOT) derivatives featuring various ring sizes and substitutions. The presence of a bulky group on the monomer resulted in a polymer possessing a more-open morphology, which promoted reversible ionic transfer. We used an electrochemical quartz crystal microbalance and cyclic voltammetry to investigate the properties of these polymers. We found that both cations and anions were involved in the charge compensation process. Furthermore, PXDOT derivatives possessing larger ring sizes and/or longer alkyl substituents exhibited less trapping of ions within the polymer during the redox process, The long-term electrochromic stability of these PXDOTs depended strongly on the number of trapped ions. Although the transmittance attenuation of poly(3,4-ethylenedioxythiophene) (PEDOT) decreased from 53 to 42 96, we observed no significant decay for poly(diethyl-3,4-dihydro-2H-thieno[3,4-b]-[1,4]dioxepine) (PProDOT-Et(2)) after 400 cycles.