Browsing by Author "Hsu, Hui-Lin"

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Erbium-Doped Amorphous Carbon-Based Thin Films: A Photonic Material Prepared by Low-Temperature RF-PEMOCVD
(2014-03-01)
Hsu, Hui-Lin
;
Leong, Keith R.
;
Teng, I-Ju
;
Halamicek, Michael
;
Juang, Jenh-Yih
The integration of photonic materials into CMOS processing involves the use of new materials. A simple one-step metal-organic radio frequency plasma enhanced chemical vapor deposition system (RF-PEMOCVD) was deployed to grow erbium-doped amorphous carbon thin films (a-C:(Er)) on Si substrates at low temperatures (<200 degrees C). A partially fluorinated metal-organic compound, tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate) Erbium(+III) or abbreviated Er(fod)(3), was incorporated in situ into a-C based host. Six-fold enhancement of Er room-temperature photoluminescence at 1.54 mu m was demonstrated by deuteration of the a-C host. Furthermore, the effect of RF power and substrate temperature on the photoluminescence of a-C:D(Er) films was investigated and analyzed in terms of the film structure. Photoluminescence signal increases with increasing RF power, which is the result of an increase in [O]/[Er] ratio and the respective erbium-oxygen coordination number. Moreover, photoluminescence intensity decreases with increasing substrate temperature, which is attributed to an increased desorption rate or a lower sticking coefficient of the fluorinated fragments during film growth and hence [Er] decreases. In addition, it is observed that Er concentration quenching begins at similar to 2.2 at% and continues to increase until 5.5 at% in the studied a-C: D(Er) matrix. This technique provides the capability of doping Er in a vertically uniform profile.
Fabrication of cone-shaped CNF/SiC-coated Si-nanocone composite structures and their excellent field emission performance
(2012)
Teng, I-Ju
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Hsu, Hui-Lin
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Jian, Sheng-Rui
;
Kuo, Cheng-Tzu
;
Juang, Jenh-Yih
Novel cone-shaped carbon nanofiber (CNF)/silicon carbide (SiC)-coated Si-nanocone (Si-NC) composite structures with excellent field emission (FE) performance have been fabricated by a simple microwave plasma chemical vapour deposition process. Transmission electron microscopy analyses reveal that the newly developed cone-shaped composite structures are composed of bamboo-like herringbone CNFs grown vertically on the tips of conical SiC layers with a flat-top Si cone embedded underneath. For this CNF/SiC-coated Si-NC composite array, a ultra-low threshold field of 0.32 V mu m(-1) (at 10 mA cm(-2)), a large emission current density of 668 mA cm(-2) at 1.05 V mu m(-1), and a field enhancement factor as high as similar to 48 349 are obtained. In addition, the FE lifetime test performed at a large emission current density of 200 mA cm(-2) under an applied field of 1 V mu m(-1) shows no discernible decay during a period of over 260 minutes. We deduce that this superior FE performance can be attributed to the specific bamboo-like herringbone CNFs with numerous open graphitic edges and a faceted top end, and the conical base SiC/ Si structures with sufficient adhesion to the substrate surface. Such a novel structure with promising emission characteristics makes it a potential material for electron field emitters.
Flexible UV-Ozone-Modified Carbon Nanotube Electrodes for Neuronal Recording
(2010-05-18)
Hsu, Hui-Lin
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Teng, I-Ju
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Chen, Yung-Chan
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Hsu, Wei-Lun
;
Lee, Yu-Tao
Carbon nanotubes were grown on flexible polyimide substrates at temperatures below 400 degrees C as electrodes for extracellularly neuronal recording. The electrical charge-transfer and electrochemical properties of such CNT electrodes were enhanced by UV-ozone exposure, which induced the formation of C-O, C=O, and O-C=O bonds and reduced the CNT/electrolyte interfacial impedance while increasing the interfacial capacitance.
Highly graphitized laterally interconnected SWCNT network synthesis via a sandwich-grown method
(2011-04-13)
Teng, I-Ju
;
Chen, Kai-Ling
;
Hsu, Hui-Lin
;
Jian, Sheng-Rui
;
Wang, Li-Chun
We present a sandwich-grown method for growing laterally interconnected single-walled carbon nanotube (SWCNT) networks with a high degree of graphitization by microwave plasma chemical vapour deposition (MPCVD). An Al(2)O(3)-supported Fe catalyst precursor layer deposited on an oxidized Si substrate with an upper Si cover is first pretreated in pure hydrogen, and then exposed to a gas mixture of methane/hydrogen for growth process at a lower growth temperature and a faster rate. The effects of various parameters, such as catalyst film thickness, gas flow rate, working pressure, growth time and plasma power, on the morphologies and structural characteristics of the SWCNT networks are investigated, and therefore provide the essential conditions for direct growth of laterally interconnected SWCNT networks. Analytical results demonstrate that the SWCNT-based lateral architecture comprises a mixture of graphene-sheet-wrapped catalyst particles and laterally interconnected nanotubes, isolated or branched or assembled into bundles. The results also show that the formation of the laterally interconnected SWCNT networks is related to the sandwich-like stack approach and the addition of an Al(2)O(3) layer in the MPCVD process. The successful growth of lateral SWCNT networks provides new experimental information for simply and efficiently preparing lateral SWCNTs on unpatterned substrates, and opens a pathway to create network-structured nanotube-based devices.
In-situ doping of erbium in hydrogenated amorphous carbon by low temperature metalorganic radio frequency plasma enhanced chemical vapor deposition
(2014-11-03)
Hsu, Hui-Lin
;
Leong, Keith R.
;
Halamicek, Michael
;
Teng, I-Ju
;
Mahtani, Pratish
A significant improvement in the photoluminescence of erbium doped amorphous carbon (a-C: H(Er)) is reported. The effects of the RF power on the anode and cathode a-C: H films were investigated in terms of the microstructural and local bonding features. It was determined that Er doped a-C: H films should be placed on the anode to obtain wider bandgap and lower percentage of sp(2) carbon bonding. The metalorganic compound, tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate) Erbium(+III) or Er(fod)(3), was incorporated in-situ into an a-C: H host by metalorganic rf plasma enhanced chemical vapor deposition. This technique provides the capability of doping Er in a vertically uniform profile. The high erbium concentration (3.9 at.%), partial fluorination of the surrounding ligands, and the large optical bandgap of the host a-C: H are the primary factors that enable enhancement of the photoluminescence. (C) 2014 Elsevier B. V. All rights reserved.
Laser, buffer layer and CoCrPtO(x)-assisted low temperature fabrication process of a small-sized-CNT pattern by MPCVD
(2010-10-01)
Teng, I-Ju
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Hong, Tsai-Hau
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Hsu, Hui-Lin
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Jian, Sheng-Rui
;
Wang, Wei-Hsiang
For improving compatibility with IC processes, this work presents a low temperature process (<400 degrees C) to fabricate a small-sized-carbon nanotube (CNT) (<6 graphene layers) pattern by buffer layer (AlN) and CoCrPtO(x) catalyst precursor-assisted microwave plasma chemical vapor deposition (MPCVD). Without high temperature heating on the whole specimen, the low temperature process mainly results from selective local activation laser heating (>= 600 degrees C) to form the catalyst nanostructures, which are beneficial to low temperature H-plasma treatment to form catalyst nanoparticles for CNT growth. The functions of the buffer layer and the catalyst precursor are to help the heat dissipation and the small-sized CNT formation. (C) 2010 Elsevier B.V. All rights reserved.
Laser, buffer layer and CoCrPtOx-assisted low temperature fabrication process of a small-sized-CNT pattern by MPCVD
(2010-10-01)
Teng, I-Ju
;
Hong, Tsai-Hau
;
Hsu, Hui-Lin
;
Jian, Sheng-Rui
;
Wang, Wei-Hsiang
For improving compatibility with IC processes, this work presents a low temperature process (<400 degrees C) to fabricate a small-sized-carbon nanotube (CNT) (<6 graphene layers) pattern by buffer layer (AlN) and CoCrPtOx catalyst precursor-assisted microwave plasma chemical vapor deposition (MPCVD). Without high temperature heating on the whole specimen, the low temperature process mainly results from selective local activation laser heating (>= 600 degrees C) to form the catalyst nanostructures, which are beneficial to low temperature H-plasma treatment to form catalyst nanoparticles for CNT growth. The functions of the buffer layer and the catalyst precursor are to help the heat dissipation and the small-sized CNT formation. (C) 2010 Elsevier B.V. All rights reserved.
On the use of new oxidized Co-Cr-Pt-O catalysts for vertically-aligned few-walled carbon nanotube forest synthesis in electron cyclotron resonance chemical vapor deposition
(2014-12-01)
Teng, I-Ju
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Huang, Chong-Sian
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Hsu, Hui-Lin
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Chung, I-Chuan
;
Jian, Sheng-Rui
A new class of the multi-element catalysis system, Co-Cr-Pt-O, is used for vertically-aligned few-walled carbon nanotube (CNT) forest synthesis by a sandwich-growth technology in electron cyclotron resonance chemical vapor deposition. The effect of catalyst compositions on the resulting particle sizes after pretreatment, and the influence of process parameters on the CNT forest heights and diameters are investigated. Results show that a plasma pretreatment step reduces the metal oxides present in the as-deposited Co-Cr-Pt-O catalyst to their metallic states or to mixed metallic/oxidic states, and the co-catalytic synergistic effect during the reduction process thus leads to the production of uniformly small particles with a size of 3.3-3.9 nm over the substrate. Moreover, with CH4 as the carbon source, vertically-aligned CNT forests of similar to 12 mu m in height are achieved, and further characterizations indicate that the forests consist of dominant triple-walled nanotubes with an average inner tube diameter of 3.2-3.7 nm mostly. Additionally, field emission measurements show that the turn-on field of the CNT-forest emitters is below 2.6 V/mu m, and the emission current density can reach 110 mA/cm(2) at 4.5 V/mu m. High reproducibility of field emission characteristics and Raman signals suggests the regularity of the CNT forests in structure and size. (C) 2014 Elsevier Ltd. All rights reserved.
Reduction of Photoluminescence Quenching by Deuteration of Ytterbium-Doped Amorphous Carbon-Based Photonic Materials
(2014-08-01)
Hsu, Hui-Lin
;
Leong, Keith R.
;
Teng, I-Ju
;
Halamicek, Michael
;
Juang, Jenh-Yih
In situ Yb-doped amorphous carbon thin films were grown on Si substrates at low temperatures (<200 degrees C) by a simple one-step RF-PEMOCVD system as a potential photonic material for direct integration with Si CMOS back end-of-line processing. Room temperature photoluminescence around 1 mu m was observed via direct incorporation of optically active Yb3+ ions from the selected Yb(fod)(3) metal-organic compound. The partially fluorinated Yb(fod)(3) compound assists the suppression of photoluminescence quenching by substitution of C-H with C-F bonds. A four-fold enhancement of Yb photoluminescence was demonstrated via deuteration of the a-C host. The substrate temperature greatly influences the relative deposition rate of the plasma dissociated metal-organic species, and hence the concentration of the various elements. Yb and F incorporation are promoted at lower substrate temperatures, and suppressed at higher substrate temperatures. O concentration is slightly elevated at higher substrate temperatures. Photoluminescence was limited by the concentration of Yb within the film, the concentration of Yb ions in the +3 state, and the relative amount of quenching due to the various de-excitation pathways associated with the vibrational modes of the host a-C network. The observed wide full-width-at-half-maximum photoluminescence signal is a result of the variety of local bonding environments due to the a-C matrix, and the bonding of the Yb3+ ions to O and/or F ions as observed in the X-ray photoelectron spectroscopy analyses.
Temperature-dependent electrical and photo-sensing properties of horizontally-oriented carbon nanotube networks synthesized by sandwich-growth microwave plasma chemical vapor deposition
(2013-02-01)
Teng, I-Ju
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Hsu, Hui-Lin
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Jian, Sheng-Rui
;
Wang, Li-Chun
;
Chen, Kai-Ling
The electrical and photo-sensing properties of horizontally-oriented interconnected carbon nanotube networks (CNT-NWs) prepared by means of a microwave plasma chemical vapor deposition sandwich-growth process are investigated. The temperature-dependent dark and illuminated current-voltage and transfer characteristics of CNT-NW-assisted devices are measured. Results show that the current-voltage characteristics of the devices exhibit nonlinear behavior, and the current can be further modulated by a gate voltage, revealing p-type semiconducting behavior with a device mobility of similar to 14.5 cm(2)/V.s and an on-off current ratio of -10(3). Moreover, when the CNT-NW-assisted devices are irradiated with 1.25-25 mu m infrared (IR) from 300 to 11 K, the photo currents increase approximately 1.1- to 2.7-fold compared to the dark currents at +/- 2 V bias voltage. Such results demonstrate that the presented CNT-NWs have high potential for IR photo-sensor applications. (C) 2012 Elsevier B.V. All rights reserved.