Browsing by Author "Dai, Wei-Syuan"

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An Extended-Gate Field-Effect Transistor With Low-Temperature Hydrothermally Synthesized SnO2 Nanorods as pH Sensor
(2012-10-01)
Li, Hung-Hsien
;
Dai, Wei-Syuan
;
Chou, Jung-Chuan
;
Cheng, Huang-Chung
;
電子工程學系及電子研究所
An extended-gate field-effect transistor (EGFET) with low-temperature hydrothermally synthesized SnO2 nanorods as the pH sensor was demonstrated for the first time. The SnO2 nanorod sensor exhibited the higher sensitivity of 55.18 mV/pH and larger linearity of 0.9952 in the wide sensing range of pH 1-13 with respect to the thin-film one. The nearly 15% sensitivity enhancement for such a sensor was attributed to the high surface-to-volume ratio of the nanorod structure, reflecting larger effective sensing areas. The characteristics of the output voltage versus sensing time also indicated good reliability and durability for the SnO2 nanorod sensor. Furthermore, the hysteresis was only 3.69 mV after the solution was changed as pH7 --> pH3 --> pH7 --> pH11 --> pH7.
Coaxial-structured ZnO/silicon nanowires extended-gate field-effect transistor as pH sensor
(2013-02-01)
Li, Hung-Hsien
;
Yang, Chi-En
;
Kei, Chi-Chung
;
Su, Chung-Yi
;
Dai, Wei-Syuan
An extended-gate field-effect transistor (EGFET) of coaxial-structured ZnO/silicon nanowires as pH sensor was demonstrated in this paper. The oriented 1-mu m-long silicon nanowires with the diameter of about 50 nm were vertically synthesized by the electroless metal deposition method at room temperature and were sequentially capped with the ZnO films using atomic layer deposition at 50 degrees C. The transfer characteristics (I-DS-V-REF) of such ZnO/silicon nanowire EGFET sensor exhibited the sensitivity and linearity of 46.25 mV/pH and 0.9902, respectively for the different pH solutions (pH 1-pH 13). In contrast to the ZnO thin-film ones, the ZnO/silicon nanowire EGFET sensor achieved much better sensitivity and superior linearity. It was attributed to a high surface-to-volume ratio of the nanowire structures, reflecting a larger effective sensing area. The output voltage and time characteristics were also measured to indicate good reliability and durability for the ZnO/silicon nanowires sensor. Furthermore, the hysteresis was 9.74 mV after the solution was changed as pH 7 -> pH 3 -> pH 7 -> pH 11 -> pH 7. (C) 2012 Elsevier B.V. All rights reserved.