Browsing by Author "Ko, T. Y."

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Electrical and Optical Properties of a Single Sb(2)Se(3) Nanorod
(2009-06-01)
Ko, T. Y.
;
Yang, C. H.
;
Sun, K. W.
;
Chang, H. W.
;
Sarkar, B.
In this paper we present the methods to chemically synthesize the Sb(2)Se(3) nanorods and study the electrical and optical properties of a single Sb(2)Se(3) nanorod with an average size of 70 nm in diameter and a length of about 1 mu m to 2 mu m. The techniques we devised can immobilize and allocate a single nano-object on an electron beam (E-beam) patterned smart substrate. It can also overcome the limitation of the spatial resolution of conventional optical techniques (similar to 1 mu m) to obtain optical spectroscopy in an individual nano-object less than 100 nm in size. We also demonstrate the techniques in using E-beam defined metallic coordination markers as electrodes to measure the conductance of a single Sb(2)Se(3) nanorod.
Electrical and Optical Properties of a Single Sb2Se3 Nanorod
(2009-06-01)
Ko, T. Y.
;
Yang, C. H.
;
Sun, K. W.
;
Chang, H. W.
;
Sarkar, B.
In this paper we present the methods to chemically synthesize the Sb2Se3 nanorods and study the electrical and optical properties of a single Sb2Se3 nanorod with an average size of 70 nm in diameter and a length of about 1 mu m to 2 mu m. The techniques we devised can immobilize and allocate a single nano-object on an electron beam (E-beam) patterned smart substrate. It can also overcome the limitation of the spatial resolution of conventional optical techniques (similar to 1 mu m) to obtain optical spectroscopy in an individual nano-object less than 100 nm in size. We also demonstrate the techniques in using E-beam defined metallic coordination markers as electrodes to measure the conductance of a single Sb2Se3 nanorod.
Electron transport mechanisms in individual cobalt-doped ZnO nanorods
(2012-11-01)
Ko, T. Y.
;
Tsai, M. -H.
;
Lee, C. -S.
;
Sun, K. W.
;
應用化學系
This study examined carrier transport in single cobalt-doped zinc oxide (Co:ZnO) nanorods in temperatures ranging from 80 to 405 K. Measurements were taken on single nanorods deposited on a Si template, where two- and four-point metallic contacts were previously made using e-beam lithography, dielectrophoresis, and focused ion beam. In both two-and four-point probe measurements, the current-voltage curves were clearly linear and symmetrical with respect to both axes. The electrical measurements were carried out according to three different measuring methods to accurately determine the resistivity of the single Co:ZnO nanorods. The Co-doped nanorods exhibited ferromagnetic behavior at room temperature. The remanence permanent magnet of the nanorods increased with increasing Co concentration, however, this was accompanied by the decrease in electrical resistivity. The transport properties were dominated by the thermal activation of electrons from the Fermi level to the conduction band for a temperature above 140-160 K, and to the impurity band at a lower temperature. The electronic transport of the nanorods was influenced by the surface states when exposed in the air.
Optical and electrical properties of single Sb(2)Se(3) nanorod
(2009-12-01)
Ko, T. Y.
;
Sun, K. W.
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
In this report. methods of solvothermal synthesis of Sb(2)Se(3) nanorods from a single-source precursor Sb[Se(2)P(O (1)Pr)(2)](3) were demonstrated The synthesized Sb(2)Se(3) nanorods were expected to have new optical and electrical properties. With the electron beam (E-beam) lithography and focus ion beam (FIB) techniques, we achieved immobilization and positioning of a single Sb(2)Se(3) nanorod on a patterned template. By using the confocal Raman microscope and two-point.-contact electrical measurement methods, we obtained optical and electrical characteristics from a single Sb(2)Se(3) nanorod (C) 2009 Elsevier B.V. All rights reserved.
Optical and electrical properties of single Sb2Se3 nanorod
(2009-12-01)
Ko, T. Y.
;
Sun, K. W.
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
In this report. methods of solvothermal synthesis of Sb2Se3 nanorods from a single-source precursor Sb[Se2P(O Pr-1)(2)](3) were demonstrated The synthesized Sb2Se3 nanorods were expected to have new optical and electrical properties. With the electron beam (E-beam) lithography and focus ion beam (FIB) techniques, we achieved immobilization and positioning of a single Sb2Se3 nanorod on a patterned template. By using the confocal Raman microscope and two-point.-contact electrical measurement methods, we obtained optical and electrical characteristics from a single Sb2Se3 nanorod (C) 2009 Elsevier B.V. All rights reserved.
Photoluminescence and Raman Spectroscopy of Single Diamond Nanoparticle
(2008)
Wang, J. Y.
;
Ko, T. Y.
;
Sun, K. W.
;
應用化學系
;
Department of Applied Chemistry
The paper reports the techniques that we have devised for immobilizing and allocating a single nanodiamond on the electron beam (E-beam) patterned smart substrate. The properly designed coordination markers on the semiconductor substrate and the high throughput of the confocal microscope provide us with a convenient tool to single out a nanodiamond with a size less than 100 nm and to study its optical properties on a single nanostructure basis. We have observed a broad PL emission centered at about 700 nm from a single nanodiamond which is due to the defects, vacancies in the nanodiamonds or the disordered carbon layer covered on the nanodiamond surface. We also observe red-shift in energy and asymmetrical broadening In linewidth of the sp(3) bonding Raman peak when the size of the single nanodiamond is decreased.
Photoluminescence and Raman spectroscopy of single diamond nanoparticle
(2008-01-01)
Sun, K. W.
;
Wang, J. Y.
;
Ko, T. Y.
;
應用化學系
;
應用化學系分子科學碩博班
The article reports techniques that we have devised for immobilizing and allocating a single nanodiamond on the electron beam (E-beam) lithography patterned semiconductor substrate. By combining the E-beam patterned smart substrate with the high throughput of a confocal microscope, we are able to overcome the limitation of the spatial resolution of optical techniques (similar to 1 mu m) to obtain the data on individual nano-object with a size range between 100 and 35 nm. We have observed a broad photoluminescence centered at about 700 nm from a single nanodiamond which is due to the defects, vacancies in the nanodiamonds, and the disordered carbon layer covered on the nanodiamond surface. We also observe red-shift in energy and broadening in linewidth of the sp(3) bonding Raman peak when the size of the single nanodiamond is reduced due to the phonon-confinement effects.
Raman spectroscopy of single nanodiamond: Phonon-confinement effects
(2008-04-14)
Sun, K. W.
;
Wang, J. Y.
;
Ko, T. Y.
;
應用化學系
;
應用化學系分子科學碩博班
In this paper, we devise techniques for immobilizing and allocating a single nanodiamond on the electron beam (e-beam) patterned smart substrate. The properly designed coordination markers on the semiconductor substrate and the high throughput of the confocal microscope provide us with a convenient tool to single out a nanodiamond with a size less than 100 nm and to study Raman spectroscopy. We observe a redshift in energy and broadening in the linewidth of the sp(3) bonding Raman peak when the size of the diamond is decreased from 90 to 35 nm. The observed shifts and linewidth broadening arise from the phonon-confinement effects and are in good agreement with calculations reported by [Ager Phys. Rev. B 43, 6491 (1991)] and [Yoshikawa Appl. Phys. Lett. 62, 3114 (1993)]. (C) 2008 American Institute of Physics.
Trapped charge-induced pyroelectric-like transient response in single high-resistivity Sb2Se3 nanowires
(2015-04-01)
Ko, T. Y.
;
Sun, K. W.
;
應用化學系
;
電子工程學系及電子研究所
;
Department of Applied Chemistry
Dynamic scanning photocurrent microscopy was applied to Sb2Se3 crystalline single nanowires (NWs) to analyze their transient photocurrent responses. These NWs exhibited switching behavior with rapid rise and decay times upon illumination by laser pulses. The estimated spectral responsivity and external quantum efficiency for a freshly-prepared NW at a bias voltage of 0.3 V and excitation wavelength of 488 nm were similar to 16.9 mA/W and similar to 42.9%, respectively. A pyroelectric-like current transient was observed with reduced spectral responsivity when nonpolar Sb2Se3 single-crystalline NWs were excited by laser pulses. Because Sb2Se3 NWs were non-pyroelectric or ferroelectric, the pyroelectric-like current could possibly be attributed to temperature dependent nonlinear space-charge distributions. Defects produced by the external electrical bias generated and re-distributed space charges in the NWs. As a result, the temperature dependent inhomogeneous electric field led to nonlinear expansions or contractions of the lattice (electrostriction) that can produce pyroelectric current. We obtained a lower bound of equivalent pyroelectric coefficient a >= 60.09 mu C/m(2) K from these materials by fitting the electrical transients. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim