Browsing by Author "Pan, Fu-Ming"

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A mechanistic study of hydrogen gas sensing by PdO nanoflake thin films at temperatures below 250 degrees C
(2015-01-01)
Chiang, Yu-Ju
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Li, Kuang-Chung
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Lin, Yi-Chieh
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Pan, Fu-Ming
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材料科學與工程學系
We prepared PdO nanoflake thin films on the SiO2 substrate by reactive sputter deposition, and studied their sensing response to H-2 at temperatures between 25 and 250 degrees C. In addition to the oxygen ionosorption model, which is used to describe the early H-2 sensing response over the temperature range studied, the H-2 sensing kinetics of the PdO thin films can be separated into three temperature regimes: temperatures below 100 degrees C, around 150 degrees C and above 200 degrees C. At temperatures below 100 degrees C, PdO reduction is the dominant reaction affecting the H-2 sensing behavior. At temperatures around 150 degrees C, Pd reoxidation kinetically competes with PdO reduction leading to a complicated sensing characteristic. Active PdO reduction by H-2 promotes the continuing growth of Pd nanoislands, facilitating dissociative oxygen adsorption and thus the subsequent Pd reoxidation in the H-2-dry air gas mixture. The kinetic competition between the PdO reduction and reoxidation at 150 degrees C leads to the observation of an inverse of the increase in the sensor conductivity. At temperatures above 200 degrees C, the PdO sensor exhibits a sensor signal monotonically increasing with the H-2 concentration, and the H-2 sensing behavior is consistent with the Mars-van-Krevelen redox mechanism.
Acetone sensing mechanism of PdO at temperatures below 250 degrees C
(2017-04-02)
Tsai, Cheng-Yu
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Chen, Yi Sheng
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Cheng, I-Kai
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Pan, Fu-Ming
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交大名義發表
Amorphous carbon coated silicon nanotips fabricated by MPCVD using anodic aluminum oxide as the template
(2007)
Chen, Te-Ming
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Pan, Fu-Ming
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Hung, Jui-Yi
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Chang, L.
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Wu, Shich-Chuan
We have used nanoporous anodic aluminum oxide (AAO) as a template to fabricate amorphous carbon (alpha-C) coated silicon nanotips by microwave plasma chemical vapor deposition (MPCVD). During the preparation of the well-ordered AAO pore channel array, an underlying TiN layer was anodically oxidized as well in the late stage of the AAO anodization, forming titanium oxide nanomasks for Si nanotip fabrication. The titanium oxide nanomasks were then used to transfer the arrangement pattern of the AAO pore channel array to the Si substrate by plasma etch in the MPCVD system and, therefore, a well-ordered Si nanotip array was produced. An alpha-C layer similar to 5 nm thick was in situ deposited on the Si nanotips during the MPCVD process. The alpha-C layer was rich in nanocrystalline graphitic carbons according to Raman and Auger electron spectroscopies. The nanocrystalline graphitic carbons in the coating and the sharp tip shape made the Si nanotip a good field emitter and a field enhancement factor of similar to 659 was obtained. (c) 2007 The Electrochemical Society.
Analysis of field emission of fabricated nanogap in Pd strips for surface conduction electron-emitter displays
(2008-04-01)
Lo, Hsiang-Yu
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Li, Yiming
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Tsai, Chih-Hao
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Pan, Fu-Ming
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材料科學與工程學系
We study the field emission (FE) property of a nanometer-scale gap structure in a palladium strip, which was fabricated by hydrogen absorption under high-pressure treatment. A vigorous cracking process could be accompanied by extensive atomic migration during the hydrogen treatment. A three-dimensional finite-difference time-domain particle-in-cell method is adopted to simulate the electron emission in a surface-conduction electron-emitter display (SED) device. Examinations of conducting characteristics, FE efficiency, the local field around the emitter, and the current density on the anode plate with one FE emitter are conducted. The image of a light spot is successfully produced on a phosphor plate, which implies that the explored electrode with nanometer separation possesses a potential SED application. Experimental observation and numerical simulation show that the proposed structure can be used as a surface conduction electron emitter and has a high FE efficiency with low turn-on voltage and a different electron emission mechanism. This study benefits the advanced SED design for a new type of electron source.
Anodic aluminum oxide as a template for CNT field emitters and AAO-CNT triode structure
(2005)
Lin, Chen-Chun
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Pan, Fu-Ming
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Liu, Mei
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Chang, Kai-Chun
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Chen, Po-Lin
We have used anodic aluminum oxide (AAO) as the template to grow carbon nanotubes (CNTs) for the application of field-emission display technology. In order to obtain optimal field emission properties, we have tried to control the density and the length of the CNTs grown from AAO pore channels by tuning the growth time and the CH4 concentration of the precursor gas mixture. AAO pore channel arrays were grown in the triode structure, which was fabricated on silicon wafers by conventional integrated circuit processes.
Anodic-aluminum-oxide templated carbon nanotubes in the field emission triode
(2007)
Lin, Chen-Chun
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Chang, Kai-Chun
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Pan, Fu-Ming
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Kuo, Cheng-Tzu
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Liu, Mei
To fabricate the field-emission triode structure, carbon nanotubes (CNT) were used as field emitters and grown in the anodic aluminum oxide (AAO). AAO thin layer with vertical pore channels was first prepared on the Si (100) substrate and was used to template the following growth of CNTs in an electron cyclotron resonance chemical vapor deposition (ECR-CVD) system. The tetraethoxysilane (TEOS) oxide and At layer were deposited on the CAITs and acted as the dielectric layer and gate electrode layers for the triode structure, respectively. Reactive ion and wet etches were then used to open the field-emission area in the triode. Field-emission characteristics of the CNT emitters have been studied and an anode turn-on field of similar to 8.05 V/mu m was measured.
Carbon-Coated Porous Aluminum Oxides Used as Spacer Overlayers to Reduce Secondary Electron Emission for Field Emission Display Applications
(2013-07-01)
Yu, Tung-Yuan
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Pan, Fu-Ming
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Chen, Cheng-Li
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Chen, Te-Ming
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Chen, Tsung-Han
Porous surface structures can mitigate the charging effect of vacuum spacers of field-emission flat panel display due to the abundance of secondary electrons (SEs) emitted from the spacers during field emission display (FED) operation. In this study, we fabricated porous anodic aluminum oxide (AAO) overlayers on glass substrates to examine the effect of carbon deposition on the reduction of SE emissions. This paper reports that uniform AAO overlayers can be simultaneously prepared on both sides of a glass plate 2 x 10 cm(2) in size. The SE emission of the AAO overlayer was examined by using an Auger electron microscope. When a small amount of carbon is evaporation-deposited on the as-prepared AAO overlayer, the SE emission efficiency is significantly decreased and the reduction in the SE emission is ascribed to the low SE yield of the carbon deposit and the suppression of SE escape from the narrowed pore channels. However, a heavy deposition of carbon results in a smaller surface roughness of the AAO overlayer, thereby increasing SE emission. The carbon-coated AAO overlayer demonstrates favorable electrical and mechanical properties, making it suitable for use in FED vacuum spacers. (C) 2013 The Japan Society of Applied Physics
Characteristics of Gate-All-Around Junctionless Polysilicon Nanowire Transistors With Twin 20-nm Gates
(2015-09-01)
Liu, Tung-Yu
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Pan, Fu-Ming
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Sheu, Jeng-Tzong
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材料科學與工程學系奈米科技碩博班
;
分子醫學與生物工程研究所
A high performance gate-all-around (GAA) junctionless (JL) polycrystalline silicon nanowire (poly-Si NW) transistor with channel width of 12 nm, channel thickness of 45 nm, and gate length of 20 nm has been successfully demonstrated, based on a simplified double sidewall spacer process. Without suffering serious short-channel effects, the GAA JL poly-Si NW device exhibits excellent electrical characteristics, including a subthreshold swing of 105 mV/dec, a drain-induced barrier lowering of 83 mV/V, and a high I-on/I-off current ratio of 7 x 10(8) (V-G = 4 V and V-D = 1 V). Such GAA JL poly-Si NW devices exhibit potential for low-power electronics and future 3-D IC applications.
Charge-trap non-volatile memories fabricated by laser-enabled low-thermal budget processes
(2015-11-02)
Huang, Wen-Hsien
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Shieh, Jia-Min
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Pan, Fu-Ming
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Yang, Chih-Chao
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Shen, Chang-Hong
We fabricated charge-trap non-volatile memories (NVMs) using low thermal budget processes, including laser-crystallization of poly-Si thin film, chemical vapor deposition deposition of a stacked memory layer, and far-infrared-laser dopant activation. The thin poly-Si channel has a low defect-density at the interface with the bulk, resulting in a steep subthreshold swing for the NVM transistors. The introduction of the stacked SiO2/AlOxNy tunnel layer and the SiNx charge-trap layer with a gradient bandgap leads to reliable retention and endurance at low voltage for the NVMs. The low thermal budget processes are desirable for the integration of the nano-scaled NVMs into system on panels. (C) 2015 AIP Publishing LLC.
CO2 laser annealing of low-hole-concentration polycrystalline germanium for the fabrication of enhancement-mode nMOSFET
(2018-10-01)
Kasirajan, Han Anand
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Huang, Wen-Hsien
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Kao, Ming-Hsuan
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Wang, Hsing-Hsiang
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Shieh, Jia-Min
A p-type polycrystalline Ge (poly-Ge) film processed by UV and CO2 laser annealing reduces the hole concentration from 6 x 10(18) to 2 x 10(16) cm(-3), accompanied by poly-grain growth. The decrease in hole concentration arises from the defect annealing using a CO2 laser, as demonstrated by the changes in the work function, that is, the valence-band maximum (VBM). The laser processes reduce the thermal budget for the fabrication of an enhancement-mode poly-Ge nMOSFET, which has a l(on)/l(off) ratio of 5 x 10(3), a Vth of 2V, and a subthreshold swing of 250 mV/dec., and will be potential fabrication methods for monolithic 3D integrated circuits in the future. (C) 2018 The Japan Society of Applied Physics
Controlled functionalization of a double-junction n(+)/n(-)/n(+) polysilicon nanobelt for hydrogen sensing application
(2016-04-01)
Nhan Ai Tran
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Sang, Chen-Hsiang
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Pan, Fu-Ming
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Sheu, Jeng-Tzong
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材料科學與工程學系奈米科技碩博班
In this paper, a double-junction n(+)/n(-)/n(+) polysilicon nanobelt selectively functionalized with platinum has been studied for hydrogen sensing application. The selective modification of the devices is performed by the combination of localized ablation of a resist and a lift-off process of e-beam evaporation of a catalyst material. The coverage of a Pt layer on the n(-) region is precisely controlled by adjusting Joule heating bias and pulse length. The Pt-functionalized devices show a rapid response to hydrogen with a limit of detection of only 5 ppm. The device with fully Pt-covered n(-) region is optimum for obtaining the best response to hydrogen. (C) 2016 The Japan Society of Applied Physics
Controlled functionalization of a double-junction n(+)/n(-)/n(+) polysilicon nanobelt for hydrogen sensing application
(2016-04)
Nhan Ai Tran
;
Sang, Chen-Hsiang
;
Pan, Fu-Ming
;
Sheu, Jeng-Tzong
;
材料科學與工程學系
In this paper, a double-junction n(+)/n(-)/n(+) polysilicon nanobelt selectively functionalized with platinum has been studied for hydrogen sensing application. The selective modification of the devices is performed by the combination of localized ablation of a resist and a lift-off process of e-beam evaporation of a catalyst material. The coverage of a Pt layer on the n(-) region is precisely controlled by adjusting Joule heating bias and pulse length. The Pt-functionalized devices show a rapid response to hydrogen with a limit of detection of only 5 ppm. The device with fully Pt-covered n(-) region is optimum for obtaining the best response to hydrogen. (C) 2016 The Japan Society of Applied Physics
Correlation of surface processes with characteristic sensing responses of PdO thin films to ethanol
(2019-04-15)
Cheng, I-Kai
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Wang, Jeng-Han
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Tsai, Cheng-Yu
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Chen, Yi-Sheng
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Pan, Fu-Ming
Gas sensing characteristics of PdO nanoflake thin films exposed to ethanol (EtOH) at temperatures below 250 degrees C was studied. The PdO thin film responses distinctly to 0.15 ppm EtOH in dry air at temperatures above 100 degrees C. A characteristic valley-shaped response feature develops in the early stage of the exposure to EtOH at 150 degrees C and above. Formation of the valley feature is a result of the combined effects of two types of surface processes, which successively modify the sensor conductance in the opposite way. Dehydrogenation of adsorbed EtOH induces reduction of preadsorbed oxygen anions and the PdO substrate, resulting in the drop of the conductance. On the other hand, subsequent adsorption of EtOH and oxygen on newly growing Pd nanoclusters, which develop due to the reduction of the PdO substrate, causes the increase in the conductance. The Pd nanoclusters can be later reoxidized in the EtOH gas mixture, thereby modifying the sensing behavior of the PdO sensor. X-ray photoelectron spectroscopy (XPS), diffusive reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature programmed desorption (TPD) were used to study adspecies and gaseous species formed in the EtOH gas sensing reactions. On the basis of the characteristic electrical response and chemical characterizations, we proposed the formation mechanism for the characteristic response feature.
Coverage Analysis for the Core/Shell Electrode of Dye-Sensitized Solar Cells
(2010-06-03)
Tien, Ta-Chang
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Pan, Fu-Ming
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Wang, Lih-Ping
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Tsai, Feng-Yu
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Lin, Ching
In this study, we established a core/shell (C/S) model that evaluates the surface coverage of an overlayer deposited on nanoparticles in terms of X-ray photoelectron spectroscopy signals of the nanoparticles. We used the model to estimate the coverage of Al(2)O(3) shell layers, which were deposited on the nanoporous TiO(2) electrodes of dye-sensitized solar cells (DSSCs) by atomic layer deposition (ALD), as a function of the number of ALD reaction cycles. The surface coverage increased with the average thickness of the Al(2)O(3) shell layers, indicating that the ALD Al(2)O(3) deposition on the nanoporous electrode was via the island growth mode. The power conversion efficiency of the DSSCs was highest after the first ALD reaction cycle for the Al(2)O(3) shell layers, which had a coverage of 0.25, according to the C/S model. The study shows that, to further improve the PCE, optimization of the ALD Al(2)O(3) deposition condition is required so that the surface coverage of the shell layer can be increased at the first ALD reaction cycle.
Dark current suppression of amorphous selenium based photosensors by the ZnO hole blocking layer
(2014-05-01)
Yu, Tung-Yuan
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Pan, Fu-Ming
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Chang, Cheng-Yi
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Hu, Tien
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Chen, Jenn-Fang
To study the influence of defects in the hole blocking layer (HBL) on the dark current of amorphous selenium (a-Se) based photosensors, we prepared ZnO thin films by reactive sputter deposition (RSD) for the use as the HBL of the photosensors. The ZnO HBL layers prepared with different oxygen flow rates were characterized by X-ray photoelectron spectroscopy, Raman scattering analysis and photoluminescence, indicating that the density of oxygen vacancies in the ZnO thin films is significantly affected by the oxygen flow rate. The deep level transient spectroscopy measurement reveals two hole trap levels present in the RSD deposited ZnO thin films; one is at 0.94 eV and the other at 0.24 eV above the valence band edge. The electrical performance of the a-Se photosensor is largely influenced by the amount of oxygen vacancies in the ZnO thin film. The a-Se photosensor with the ZnO HBL of the most oxygen vacancies has the lowest dark current and demonstrates the highest breakdown field. (C) 2014 Elsevier B.V. All rights reserved.
Double-metal-gate nanocrystalline Si thin film transistors with flexible threshold voltage controllability
(2013-11-11)
Chiou, Uio-Pu
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Shieh, Jia-Min
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Yang, Chih-Chao
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Huang, Wen-Hsien
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Kao, Yo-Tsung
We fabricated nano-crystalline Si (nc-Si: H) thin-film transistors (TFTs) with a double-metal-gate structure, which showed a high electron-mobility (mu(FE)) and adjustable threshold voltages (V-th). The nc-Si: H channel and source/drain (S/D) of the multilayered TFT were deposited at 375 degrees C by inductively coupled plasma chemical vapor deposition. The low grain-boundary defect density of the channel layer is responsible for the high mu(FE) of 370 cm(2) /V-s, a steep subthreshold slope of 90 mV/decade, and a low V-th of -0.64 V. When biased with the double-gate driving mode, the device shows a tunable V-th value extending from -1V up to 2.7 V. (C) 2013 AIP Publishing LLC.
Effect of hole blocking dielectric layer on microstructure and photoconducting properties of polycrystalline Se thin films
(2018-09-01)
Chang, Cheng-Yi
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Lin, Yi-Jie
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Huang, Yu-Wei
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Liao, Jye-Yow
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Lin, Jian-Siang
We fabricated polycrystalline selenium (c-Se) based photodetectors using three different dielectrics (HfO2, Al2O3 and SiO2) as the hole blocking layer (HBL), and studied the influence of the HBLs on the photoconducting performance of the photodetectors. The microstructure of the c-Se layer is greatly influenced by the nucleation behavior of the tellurium (Te) adhesion layer deposited between the c-Se layer and the HBLs. The photoconducting performance of the photodetectors is basically dependent on the barrier height at the junctions of the HBL with the tin-doped indium oxide (ITO) anode and with the c-Se layer. A higher barrier height at the HBL/ITO junction leads to a lower dark current density (I-D) of the photodetectors. However, the photodetector with the SiO2 HBL exhibits the largest I-D as the bias exceeds 2 V although it has the highest junction barrier height. We attribute the abnormity to the rugged morphology of the c-Se layer, which is a result of a less dense Te nucleation on the SiO2 HBL. The photocurrent density (I-ph) is inversely related to the junction barrier height at the HBL/c-Se contact. The c-Se photodetector with the HfO2 HBL has the largest I-Ph and the one with the SiO2 HBL has the smallest. The photodetector with the HfO2 HBL exhibits a quantum efficiency of 89% at 6 V.
Effect of Process Variation on Field Emission Characteristic in Surface Conduction Electron-Emitters
(2007)
Lo, Hsiang-Yu
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Li, Yiming
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Chao, Hsueh-Yung
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Tsai, Chih-Hao
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Pan, Fu-Ming
In this work, we explore the effect of process variation on field emission characteristics in surface conduction electron-emitters. The structure of palladium thin-film emitter is fabricated on the substrate and the nanometer scaled gap is formed by the focused ion beam (FIB) technique. Different shapes of nanogaps due to the process variations are investigated by the experiment and 3D Maxwell particle-in-cell simulation. Four deformation structures are examined, and it is found that the Type 1 exhibits high emission efficiency due to a stronger electric field around the apex and larger the emission current among structures. The electron emission current is dependent upon the angle of inclination of surface.
Effect of process variation on field emission characteristics in surface-conduction electron emitters
(2008-07-01)
Lo, Hsiang-Yu
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Li, Yiming
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Tsai, Chih-Hao
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Chao, Hsueh-Yung (Robert)
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Pan, Fu-Ming
In this paper, we explore the effect of process variation on field emission characteristics in surface-conduction electron emitters. The structure of Pd thin-film emitter is fabricated on the substrate and the nanometer scale gap is formed by the focused ion beam technique. Different shapes of nanogaps due to the process variations are investigated by the experiment and three-dimensional Maxwell particle-in-cell simulation. Four deformation structures are examined, and it is found that the type I exhibits high emission efficiency due to a stronger electric field around the apex and larger emission current among structures. The electron emission current is dependent upon the angle of inclination of surface. Hydrogen plasma treatment is also used to increase the edge roughness of the nanogap and thereby dramatically improve the field emission characteristics. For the nanogap with a separation of 90 nm, the turn-on voltage significantly reduces from 60 to 20 V after the hydrogen plasma treatment.
Effect of Surface Reduction Treatments of Plasma-Enhanced Atomic Layer Chemical Vapor Deposited TaN(x) on Adhesion with Copper
(2010-01-01)
Chang, Chih-Chieh
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Pan, Fu-Ming
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Chen, Ching-Wen
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材料科學與工程學系
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Department of Materials Science and Engineering
This study performs surface reduction treatments, including hydrogen plasma treatment and rapid thermal anneal (RTA) in hydrogen ambient, to reduce the nitrogen content in the surface layer of the TaN(x) ultrathin film deposited by plasma-enhanced atomic layer deposition (PE-ALD). A four-point bend delamination test and a pull-off tensile test are used to study the interfacial strength of the PE-ALD thin film with copper. According to X-ray photoelectron spectroscopy and Auger electron spectroscopy, a new chemical phase with a very small nitrogen content, possibly beta-TaN(x), is formed on the PE-ALD TaN(x) thin film after the RTA treatment. The increase in the Ta/N atomic ratio in the RTA-treated TaN(x) thin film significantly improves the adhesion of the TaN(x) film with the sputter-deposited Cu layer. However, the hydrogen-plasma-treated TaN(x) thin film shows a slight decrease in nitrogen content but still demonstrates better adhesion with the Cu layer compared with the as-deposited one. While the Cu overlayer on the RTA-treated PE-ALD TaN(x) thin film can sustain the thermal anneal at 600 degrees C, the one on the as-deposited TaN(x) thin film exhibits voiding even at a temperature as low as 400 degrees C.