Browsing by Author "Ko, Ting-Yu"

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Field-effect-dependent thermoelectric power in highly resistive Sb2Se3 single nanowire
(2018-04-01)
Sun, Kien Wen
;
Ko, Ting-Yu
;
Shellaiah, Muthaiah
;
應用化學系
;
電機學院
In this paper, we report the results of our experiments on and measurements of electrical resistivity and thermoelectric power (Seebeck coefficient) from single-crystalline antimony triselenide (Sb2Se3) single nanowires (NWs) with high resistivity (sigma similar to 4.37 x 10(-4) S/m). A positive Seebeck coefficient of approximately 661 mu V/K at room temperature was obtained using a custom-made thermoelectric power probe with an alternating current lock-in method (the 2 omega technique), which indicates that the thermal transport is dominated by holes. The measured Seebeck coefficient of the NWs is a factor of 2-3 lower than their bulk counterparts and is comparable to that of a highly conductive Sb2Se3 single NWs (approximately -750 mu V/K). We observed an increase in the Seebeck coefficients with increased bias voltages by field-effect gating, which cannot be explained by the modulation of the Fermi level in the NWs.
Spectroscopy of a single Sb(2)Se(3) nanorod
(2009-08-01)
Sun, Kien Wen
;
Yang, Cheng-Hang
;
Ko, Ting-Yu
;
Chang, Hao-Wei
;
Liu, Chen-Wei
In this paper, we present solvothermal methods to chemically synthesize Sb(2)Se(3) nanorods using dialkyl diselenophosphate (dsep) complexes of antimony. Energy-dispersive X-ray analysis shows the products are phase pure. We have also studied the Raman and photoluminescence spectroscopy of a single Sb(2)Se(3) nanorod with an average size of 60 nm in diameter and a length less than 1 mu m. Techniques have been devised to immobilize and allocate a single nano-object on an electron beam (E-beam) patterned smart substrate with metallic coordination markers. This also overcomes the limitation of spatial resolution of conventional Optical techniques (similar to 1 mu m) to perform optical spectroscopy on an individual nano-object less than 100 nm in size. Raman spectroscopy reveals that Sb(2)Se(3) nanorods synthesized at a lower temperature contain a small amount of Sb(2)Se(3). The broad linewidth observed in luminescence spectra from a single rod is attributed to the increasing number of surface defects, impurities, and dangle bonds attached on the surface as the nanoparticle size reduced to nanometer scale.
Spectroscopy of a single Sb2Se3 nanorod
(2009-08-01)
Sun, Kien Wen
;
Yang, Cheng-Hang
;
Ko, Ting-Yu
;
Chang, Hao-Wei
;
Liu, Chen-Wei
In this paper, we present solvothermal methods to chemically synthesize Sb2Se3 nanorods using dialkyl diselenophosphate (dsep) complexes of antimony. Energy-dispersive X-ray analysis shows the products are phase pure. We have also studied the Raman and photoluminescence spectroscopy of a single Sb2Se3 nanorod with an average size of 60 nm in diameter and a length less than 1 mu m. Techniques have been devised to immobilize and allocate a single nano-object on an electron beam (E-beam) patterned smart substrate with metallic coordination markers. This also overcomes the limitation of spatial resolution of conventional Optical techniques (similar to 1 mu m) to perform optical spectroscopy on an individual nano-object less than 100 nm in size. Raman spectroscopy reveals that Sb2Se3 nanorods synthesized at a lower temperature contain a small amount of Sb2Se3. The broad linewidth observed in luminescence spectra from a single rod is attributed to the increasing number of surface defects, impurities, and dangle bonds attached on the surface as the nanoparticle size reduced to nanometer scale.
Thermal and Thermoelectric Transport in Highly Resistive Single Sb2Se3 Nanowires and Nanowire Bundles
(2016-10-07)
Ko, Ting-Yu
;
Shellaiah, Muthaiah
;
Sun, Kien Wen
;
應用化學系
;
電子工程學系及電子研究所
In this study, we measured the thermal conductivity and Seebeck coefficient of single Sb2Se3 nanowires and nanowire bundles with a high resistivity (sigma similar to 4.37 x 10(-4) S/m). Microdevices consisting of two adjacent suspended silicon nitride membranes were fabricated to measure the thermal transport properties of the nanowires in vacuum. Single Sb2Se3 nanowires with different diameters and nanowire bundles were carefully placed on the device to bridge the two membranes. The relationship of temperature difference on each heating/sensing suspension membranes with joule heating was accurately determined. A single Sb2Se3 nanowire with a diameter of similar to 680 nm was found to have a thermal conductivity (k(NW)) of 0.037 +/- 0.002 W/m.K. The thermal conductivity of the nanowires is more than an order of magnitude lower than that of bulk materials (k similar to 0.36-1.9 W/m.K) and highly conductive (sigma similar to 3 x 10(4) S/m) Sb2Se3 single nanowires (k similar to 1 W/m.K). The measured Seebeck coefficient with a positive value of similar to 661 mu V/K is comparable to that of highly conductive Sb2Se3 single nanowires (similar to 750 mu V/K). The thermal transport between wires with different diameters and nanowire bundles was compared and discussed.