Browsing by Author "Wang, Chia-Hsin"

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Anti-site defect effect on the electronic structure of a Bi2Te3 topological insulator
(2018-01-01)
Chuang, Pei-Yu
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Su, Shu-Hsuan
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Chong, Cheong-Wei
;
Chen, Yi-Fan
;
Chou, Yu-Heng
Tuning the Fermi level (EF) in Bi2Te3 topological-insulator (TI) films is demonstrated on controlling the temperature of growth with molecular-beam epitaxy (MBE). Angle-resolved photoemission spectra (ARPES) reveal that EF of Bi2Te3 thin films shifts systematically with the growth temperature (Tg). The key role that a Bi-on-Te(1) (BiTe1) antisite defect plays in the electronic structure is identified through extended X-ray-absorption fine-structure (EXAFS) spectra at the Bi L-3-edge. Calculations of electronic structure support the results of fitting the EXAFS, indicating that the variation of EF is due to the formation and suppression of BiTe1 that is tunable with the growth temperature. Our findings provide not only insight into the correlation between the defect structure and electronic properties but also a simple route to control the intrinsic topological surface states, which could be useful for applications in TIbased advanced electronic and spintronic devices.
Deposition of mesoporous silicon carbide thin films from (Me3Si)(4)Sn: Tin nanoparticles as in situ generated templates
(2007-10-30)
Wang, Chia-Hsin
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Shen, Wen-Yih
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Sheng, Pei-Sun
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Lee, Chi-Young
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Chiu, Hsin-Tien
With use of Sn(SiMe3)(4) as the precursor, amorphous SiC1+x thin films with Sri nanoparticles embedded were grown on Si substrates at 923 K by low-pressure chemical vapor deposition. After treatment under hydrogen plasma at 923 K, the Sri nanoparticles in the films were removed by an HF solution and by evaporation at 1423 K. Following the removal of Sri, high-temperature treatments at 1273-1423 K converted the amorphous thin films into mesoporous semiconducting beta-SiC thin films with pore sizes 10-100 nm.
Growth of high-aspect-ratio gold nanowires on silicon by surfactant-assisted galvanic reductions
(2008-06-03)
Huang, Ting-Kai
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Chen, Ying-Chieh
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Ko, Hsin-Chun
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Huang, Hsin-Wei
;
Wang, Chia-Hsin
A simple galvanic reduction for direct growth of An nanowires on silicon wafers is developed. The nanowires were prepared by reacting HAuCl4(aq) with Sn-(s) in the presence of CTAC((aq)) (cetyltrimethylammonium chloride) and NaNO3(aq), which were important to the product morphology development. The nanowire diameter was 50-100 nm, and the length was more than 20 mu m.
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).
Preparation of Mo2C@a-C core-shell powders via carburization of Mo particles by 1-chlorobutane and hexachlorobenzene
(2007-07-01)
Chien, Chun-Hsiung
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Sheng, Pei-Sun
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Wang, Chia-Hsin
;
Huang, Chih-Hao
;
Lin, Huang-Kai
Mo2C@a-C core-shell powders were prepared by reacting Mo powders with gaseous 1-chlorobutane or hexachlorobenzene at 1173 K. The chlorinated reactants acted as the source of carbon for the carburization of Mo and the source of chlorine, which assists the etching of Mo to reduced particle sizes. (C) 2006 Elsevier B.V. All rights reserved.
Role of Tin Chloride in Tin-Rich Mixed-Halide Perovskites Applied as Mesoscopic Solar Cells with a Carbon Counter Electrode
(2016-12)
Tsai, Cheng-Min
;
Wu, Hui-Ping
;
Chang, Sun-Tang
;
Huang, Chi-Feng
;
Wang, Chia-Hsin
We report the synthesis and characterization of alloyed Sn Pb methylammonium mixed-halide perovskites (CH3NH3SnyPb1-yI3-xClx) to extend light harvesting toward the near infrared region for carbon-based mesoscopic solar cells free of organic hole-transport layers. The proportions of Sn in perovskites are well controlled by mixing tin chloride (SnCl2) and lead iodide (Pbl(2)) in varied stoichiometric ratios (y = 0-1). SnCl2 plays a key role in modifying the lattice structure of the perovskite, showing anomalous optical and optoelectronic properties; upon increasing the concentration of SnC2, the variation of the band gap and band energy differed from those of the Snl(2) precursor. The CH3NH3SnyPb1-yI3-xClx devices showed enhanced photovoltaic performance upon increasing the proportion of SnCl2 until y = 0.75, consistent with the corresponding potential energy levels. The photovoltaic performance was further improved upon adding 30 mol % tin fluoride (SnF2) with device configuration FTO/TiO2/Al2O3/NiO/C, producing the best power conversion efficiency, 5.13%, with great reproducibility and intrinsic stability.
Silicon carbide nanostructures from reactions between vapors of organochlorosilanes and liquid of sodium-factors affecting morphology and composition
(2007-12-01)
Wang, Chia-Hsin
;
Liu, Wen-Chih
;
Lee, Chi-Young
;
Chiu, Hsin-Tien
;
應用化學系
Cubic shells and spherical nanoparticles of beta-SiC were produced at 1273 K by processing the ceramic precursors formed from the reactions between vapors of organochlorosilanes, Me2SiCl2, MeSiCl3, MeSiHCl2, and PhSiCl3, and liquid Na at 523-723 K. From Me2SiCl2, a flexible linear polycarbosilane precursor was synthesized and covered the NaCl byproduct surface to form a cubic shape. Hollow cubic beta-SiC shells were produced after the NaCl templates were removed. From MeSiCl3, a rigid cross-linked polycarbosilane was produced and phase segregated from the NaCl byproduct. The precursor was transformed into nanoparticles without special morphology. MeSiHCl2 produced a cross-linked polysilane precursor at low temperatures, which can be converted into a mixture of beta-SiC and Si nanoparticles. At high temperatures, the polysilane converted to polycarbosilane and produced hollow cubic beta-SiC shells. The carbon-rich PhSiCl3 generated cube-like particles as the final product, which contained beta-SiC and carbon.
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