Browsing by Author "Lin, I-Nan"

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Effects of size and shell thickness of TiO2 hierarchical hollow spheres on photocatalytic behavior: An experimental and theoretical study
(2014-04-05)
Tsai, Min-Chiao
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Lee, Jeng-Yi
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Chen, Po-Chin
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Chang, Yuan-Wei
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Chang, Ya-Chen
Through a self-sacrificing template method, highly uniform hollow-spheres of TiO2 anatase are synthesized with controllable diameter from 365 nm to 930 nm. Compared to large hollow spheres, a large enhancement in the photocatalytic activity is reported for the small hollow spheres (with a thickness of 50 nm). By extending Mie\'s scattering theory from solid- to hollow-spheres, for a spherical scatter with a diameter of 300-900 nm, theoretical calculation reveal that each singular hollow sphere has absorption power equivalent to a solid sphere as the shell thickness parameter reaches a critical value of 0.3-0.6. This critical thickness parameter is independent to the size of a single hollow sphere, demonstrating that hollow spheres have quantitative advantages over solid spheres of the same weight. Moreover, calculation supported that small hollow spheres have stronger absorption power than large hollow spheres due to higher thickness. This greatly enhance the performance of small hollow spheres under a photocatalytic test. Our theoretical results showed good agreement to the experimental measurements, and provided a framework for the design of hollow-sphere nano-particles for optimized absorption power. (C) 2013 Elsevier B.V. All rights reserved.
Electron field emission properties on ultra-nano-crystalline diamond coated silicon nanowires
(2008-07-01)
Tzeng, Yu-Fen
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Lee, Chi-Young
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Chiu, Hsin-Tien
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Tai, Nyan-Hwa
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Lin, I-Nan
Ultra-nano-crystal line diamond (UNCD) nano-emitters were prepared by coating UNCD films on the tip of silicon nanowire (SiNW) templates by microwave plasma-enhanced chemical vapor deposition process. The electron field emission properties of the UNCD/SiNW nano-emitters varied markedly with the pre-seeding process for the SiNW-templates. The direct ultrasonication process is more efficient in the formation of the diamond nuclei than the carburization/ultrasonication process, yielding UNCD/SiNWs nano-emitters with better electron field emission properties. The electron field emission can be turned on at (E(0))(UNCD/SiNW4)= 3.75 V/mu m, yielding a large electron field emission current density of (Je)(UNCD/SiNW4)= 11.22 mA/cm(2) at an applied field of 9.75 V/mu m. These characteristics are significantly better than those of bare SiNWs or planar UNCD films. (C) 2008 Elsevier B.V. All rights reserved.
Electron field emission properties on UNCD coated Si-nanowires
(2008-04-01)
Tzeng, Yu-Fen
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Lee, Yen-Chih
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Lee, Chi-Young
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Chiu, Hsin-Tien
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Lin, I-Nan
The electron field emission (EFE) properties of Si-nanowires (SiNW) were improved by coating a UNCD films on the SiNWs. The SiNWs were synthesized by an electroless metal deposition (EMD) process, whereas the UNCD films were deposited directly on bare SiNW templates using Ar-plasma based microwave plasma enhanced chemical vapor deposition (MPE-CVD) process. The electron field emission properties of thus made nano-emitters increase with MPE-CVD time interval for coating the UNCD films, attaining small turn-on field (E(0)=6.4 V/mu m) and large emission current density (J(e)=6.0 mA/cm(2) at 12.6 V/mu m). This is presumably owing to the higher UNCD granulation density and better UNCD-to-Si electrical contact on SiNWs. The electron field emission behavior of these UNCD nanowires emitters is significantly better than the bare SiNW ((E(0))(SiNWs)=8.6 V/mu m and (J(e))(SiNWs)<0.01 mA/cm(2) at the same applied field) and is comparable to those for carbon nanotubes. (C) 2008 Elsevier B.V. All rights reserved.
Exploring Topological Defects in Epitaxial BiFeO(3) Thin Films
(2011-02-01)
Vasudevan, Rama K.
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Chen, Yi-Chun
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Tai, Hsiang-Hua
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Balke, Nina
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Wu, Pingping
Using a combination of piezoresponse force microscopy (PFM) and phase-field modeling, we demonstrate ubiquitous formation of center-type and possible ferroelectric closure domain arrangements during polarization switching near the ferroelastic domain walls in (100) oriented rhombohedral BiFeO(3). The formation of these topological defects is determined from the vertical and lateral PFM data and confirmed from the reversible changes in surface topography. These observations provide insight into the mechanisms of tip-induced ferroelastic domain control and suggest that formation of topological defect states under the action of local defect- and tip-induced fields is much more common than previously believed.
Exploring Topological Defects in Epitaxial BiFeO3 Thin Films
(2011-02-01)
Vasudevan, Rama K.
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Chen, Yi-Chun
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Tai, Hsiang-Hua
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Balke, Nina
;
Wu, Pingping
Using a combination of piezoresponse force microscopy (PFM) and phase-field modeling, we demonstrate ubiquitous formation of center-type and possible ferroelectric closure domain arrangements during polarization switching near the ferroelastic domain walls in (100) oriented rhombohedral BiFeO3. The formation of these topological defects is determined from the vertical and lateral PFM data and confirmed from the reversible changes in surface topography. These observations provide insight into the mechanisms of tip-induced ferroelastic domain control and suggest that formation of topological defect states under the action of local defect- and tip-induced fields is much more common than previously believed.
Fabrication of an ultra-nanocrystalline diamond-coated silicon wire array with enhanced field-emission performance
(2007-10-31)
Tzeng, Yu-Fen
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Liu, Kao-Hsiang
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Lee, Yen-Chih
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Lin, Sue-Jian
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Lin, I-Nan
Large- area ultra- nanocrystalline diamond- coated silicon nanowire ( UNCD/ SiNW) field- emitter arrays were prepared by the deposition of ultra- nanocrystalline diamond ( UNCD) on the tips of arrays of silicon nanowires ( SiNWs) with uniform diameters. The electron field- emission ( EFE) behavior of UNCD/ SiNW arrays as well as that of the SiNW arrays has been observed. The SiNWs exhibit good electron field- emission properties with turn- on fields ( E0) of about 7.6 V mu m- 1, which is superior to the EFE properties of planar- silicon materials. The turn- on fields are related to the diameter of the SiNWs. Coating the SiNWs with a UNCD film further improves their EFE properties. The threshold field for attaining J(e) = 0.1 mAcm(-2) EFE current density is 16.0 V mu m(-1) for bare SiNWs and 10.2 V mu m(-1) for UNCD/ SiNWs. The improvement in EFE properties due to the UNCD coating is presumably due to the lower work function of field emission of the UNCD materials, compared to that of the silicon materials.
Growth of polycrystalline tubular silicon carbide Yajima-type reaction at the vapor-solid interface
(2007-08-07)
Wang, Chia-Hsin
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Lin, Huang-Kai
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Ke, Tsung-Ying
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Palathinkal, Thomas-Joseph
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Tai, Nyan-Hwa
Polycrystalline tubular SiC on Si is prepared by reacting MeSiHCl2 vapor and Ca thin film on Si at 773-923 K followed by heat treatment at 1273 K. The reaction is a solvent-free Yajima-type process taking place at the vapor-solid interface. The products phase-segregate into a cable-like radial heterostructure composed of a core of CaCl2 and a shell of SiCxHy. After removal of the CaCl2 core, the layer of polycrystalline SiC tubes on Si can emit electrons at a low applied field of 2.5 V/mu m with a current of 10 mu A/cm(2).
Investigation of the spectral characteristics of silicon-vacancy centers in ultrananocrystalline diamond nanostructures and single crystalline diamond
(2020-01-21)
Kunuku, Srinivasu
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Chen, Yen-Chun
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Chen, Chien-Hsu
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Kandasami, Asokan
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Chang, Wen-Hao
Silicon-vacancy (SiV) centers were produced in single crystalline diamond (SCD) and ultrananocrystalline diamond (UNCD) nanostructures via Si ion implantation or in situ Si doping. SiV-embedded UNCD (SiV-UNCD) was fabricated by both top-down and bottom-up methods. The spectral properties of the SiV centers, including the zero phonon line (ZPL) width and decay time, were investigated in the SCD and UNCD nanostructures. All the SiV-UNCD nanostructures showed bright emission regardless of the preparation method. However, the decay time of the SiV centers was affected by the synthesis procedure. A SiV decay time of tau similar to 0.19 ns was observed for UNCD nanostructures formed by in situ doping, whereas the SiV decay time was similar to 0.43 ns for SiV-UNCD clusters prepared by Si ion implantation into UNCD deposited on Ti/sapphire substrates. The ultrasonication of UNCD clusters on Ti/sapphire pyramids produced bright SiV-UNCD nanoclusters with sizes of similar to 50 nm, a ZPL width of 13.5 nm, and a decay time of 0.35 ns, suggesting promising potential in bioimaging applications. SiV-containing SCD (type Ia or type IIa) showed enhanced SiV spectral properties with a ZPL width of 6.08 nm and longer decay time of 1.3 ns. Published under license by AIP Publishing.
Investigations on Diamond Nanostructuring of Different Morphologies by the Reactive-Ion Etching Process and Their Potential Applications
(2013-08-14)
Kunuku, Srinivasu
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Sankaran, Kamatchi Jothiramalingam
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Tsai, Cheng-Yen
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Chang, Wen-Hao
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Tai, Nyan-Hwa
We report the systematic studies on the fabrication of aligned, uniform, and highly dense diamond nanostructures from diamond films of various granular structures. Self-assembled Au nanodots are used as a mask in the self-biased reactive-ion etching (RIE) process, using an O-2/CF4 process plasma. The morphology of diamond nanostructures is a close function of the initial phase composition of diamond. Cone-shaped and tip-shaped diamond nanostructures result for microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) films, whereas pillarlike and grasslike diamond nanostructures are obtained for Ar-plasma-based and N-2-plasma-based ultrananocrystalline diamond (UNCD) films, respectively. While the nitrogen-incorporated UNCD (N-UNCD) nanograss shows the most-superior electron-field-emission properties, the NCD nanotips exhibit the best photoluminescence properties, viz, different applications need different morphology of diamond nanostructures to optimize the respective characteristics. The optimum diamond nanostructure can be achieved by proper choice of granular structure of the initial diamond film. The etching mechanism is explained by in situ observation of optical emission spectrum of RIE plasma. The preferential etching of sp(2)-bonded carbon contained in the diamond films is the prime factor, which forms the unique diamond nanostructures from each type of diamond films. However, the excited oxygen atoms (O*) are the main etching species of diamond film.
One-Step Ge/Si Epitaxial Growth
(2011-07-01)
Wu, Hung-Chi
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Lin, Bi-Hsuan
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Chen, Huang-Chin
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Chen, Po-Chin
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Sheu, Hwo-Shuenn
Fabricating a low-cost virtual germanium (Ge) template by epitaxial growth of Ge films on silicon wafer with a Ge(x)Si(1-x) (0 < x < 1) graded buffer layer was demonstrated through a facile chemical vapor deposition method in one step by decomposing a hazardousless GeO(2) powder under hydrogen atmosphere without ultra-high vacuum condition and then depositing in a low-temperature region. X-ray diffraction analysis shows that the Ge film with an epitaxial relationship is along the in-plane direction of Si. The successful growth of epitaxial Ge films on Si substrate demonstrates the feasibility of integrating various functional devices on the Ge/Si substrates.
Self-carbonized lamellar nano/micro hierarchical structure C/TiO2 and its Li-ion intercalation performance
(2012)
Chen, Po-Chin
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Tsai, Min-Chiao
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Chen, Huang-Chin
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Lin, I-Nan
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Sheu, Hwo-Shuenn
In this study, two new layered titanates, fibrillar TiO2 center dot(CH3COOH)(1.4) and chrysanthemum-like TiO2 center dot(CH3COOH)(0.9) (named as FT and CT) with acetic acid and acetate intercalation have been synthesized by reacting titanium isopropoxide (TTIP) with acetic acid at different temperatures. Furthermore, nano/micro hierarchical structure TiO2 with high TiO2-B/anatse ratio was obtained by annealing the titanate (CT). For use as an anode for lithium ion batteries, uniform carbon coated titanium dioxide with high TiO2-B content was obtained by "self-carbonizing'' CT under argon atmosphere at 350 degrees C, and the compound was named SC-CT350. The capacity of the anode made from SC-CT350 can reach 144 mA h g(-1) under a high charging/discharging rate (10 C) and showed excellent retention ability.
Stacked Silicon Nanowires with Improved Field Enhancement Factor
(2010-02-01)
Tzeng, Yu-Fen
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Wu, Hung-Chi
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Sheng, Pei-Sun
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Tai, Nyan-Hwa
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Chiu, Hsin Tien
This work describes newly structured stacked silicon nanowires (s-SiNWs), consisting of nanosized silicon wires on top of silicon microrods (SiMRs) and exhibiting pronouncedly superior electron held emission (EFE) characteristics to the conventional SiNWs, by using a two-step electroless metal deposition process. Experimental results indicate that for these s-SiNWs, the electrostatic "screen effect" is markedly suppressed and the held enhancement factor (beta-value) is significantly increased ((beta)(s-SiNWs) = 2533). Additionally, the turn-on held (Eo) for triggering the EFE process is reduced to a level comparable with that of carbon nanotubes, viz. (E(0))(s-SiNWs) = 2.0 V/mu m. This simple and robust modified electroless metal deposition approach does not require either a high temperature or an expensive photolithographic process and possesses great potential for applications.
Structural and Electrical Properties of Conducting Diamond Nanowires
(2013-02-27)
Sankaran, Kamatchi Jothiramalingam
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Lin, Yen-Fu
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Jian, Wen-Bin
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Chen, Huang-Chin
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Panda, Kalpataru
Conducting diamond nanowires (DNWs) films have been synthesized by N-2-based microwave plasma enhanced chemical vapor deposition. The incorporation of nitrogen into DNWs films is examined by C Is X-ray photoemission spectroscopy and morphology of DNWs is discerned using field-emission scanning electron microscopy and transmission electron microscopy (TEM). The electron diffraction pattern, the visible-Raman spectroscopy, and the near-edge X-ray absorption fine structure spectroscopy display the coexistence of sp(3) diamond and sp(2) graphitic phases in DNWs films. In addition, the microstructure investigation, carried out by high-resolution TEM with Fourier transformed pattern, indicates diamond grains and graphitic grain boundaries on surface of DNWs. The same result is confirmed by scanning tunneling microscopy and scanning tunneling spectroscopy (STS). Furthermore, the STS spectra of current-voltage curves discover a high tunneling current at the position near the graphitic grain boundaries. These highly conducting regimes of grain boundaries form effective electron paths and its transport mechanism is explained by the three-dimensional (3D) Mott's variable range hopping in a wide temperature from 300 to 20 K. Interestingly, this specific feature of high conducting grain boundaries of DNWs demonstrates a high efficiency in field emission and pave a way to the next generation of high-definition flat panel displays or plasma devices.
Synthesis of SiV-diamond particulates via the microwave plasma chemical deposition of ultrananocrystalline diamond on soda-lime glass fibers
(2016-10-01)
Kunuku, Srinivasu
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Chen, Yen-Chun
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Yeh, Chien-Jui
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Chang, Wen-Hao
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Manoharan, Divinah
Wereport the synthesis of silicon-vacancy (SiV) incorporated spherical shaped ultrananocrystalline diamond (SiV-UNCD) particulates (size similar to 1 mu m) with bright luminescence at 738 nm. For this purpose, different granular structured polycrystalline diamond films and particulates were synthesized by using three different kinds of growth plasma conditions on the three types of substrate materials in the microwave plasma enhanced CVD process. The grain size dependent photoluminescence properties of nitrogen vacancy (NV) and SiV color centers have been investigated for different granular structured diamond samples. The luminescence of NV center and the associated phonon sidebands, which are usually observed in microcrystalline diamond and nanocrystalline diamond films, were effectively suppressed in UNCD films and UNCD particulates. Micron sized SiV-UNCD particulates with bright SiV emission has been attained by transfer of SiV-UNCD clusters on soda-lime glass fibers to inverted pyramidal cavities fabricated on Si substrates by the simple crushing of UNCD/soda-lime glass fibers in deionized water and ultrasonication. Such a plasma enhanced CVD process for synthesizing SiV-UNCD particulates with suppressed NV emission is simple and robust to attain the bright SiV-UNCD particulates to employ in practical applications.
Ti5Si3 nanowire and its field emission property
(2008-04-08)
Lin, Huang-Kai
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Tzeng, Yu-Fen
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Wang, Chia-Hsin
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Tai, Nyan-Hwa
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Lin, I-Nan