Browsing by Author "Lo, Po-Yuan"

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A carbon nanotube field effect transistor with tunable conduction-type by electrostatic effects
(2006-07-01)
Chen, Bae-Horng
;
Wei, Jeng-Hua
;
Lo, Po-Yuan
;
Wang, Hung-Hsiang
;
Lai, Ming-Jinn
In this paper, we report a conduction-type-tunable carbon nanotube field effect transistor (CNT-FET) with double-gate structure (DG CNT-FET). In this study, a specially designed narrow top-gate is created to modulate the energy band in the middle region of a single CNT. In the proposed DG device structure, the top-gate and bottom-gate biases exhibit independent modulation behaviors. Depending on whether a positive or negative bias is applied to the top-gate, the CNT-FET can be operated in either n- or p-type conduction. Energy band diagram conducive to the physical mechanisms of the proposed DG CNT-FET device structure is proposed. Based on the proposed hypothesis, ambipolar CNT-FETs can indeed be converted to n- or p-type-like behaviors. (c) 2006 Elsevier Ltd. All rights reserved.
Novel method of converting metallic-type carbon nanotubes to semiconducting-type carbon nanotube field-effect transistors
(2006-04-01)
Chen, Bae-Horng
;
Wei, Jeng-Hua
;
Lo, Po-Yuan
;
Pei, Zing-Way
;
Chao, Tien-Sheng
Depending on the chirality, single-walled carbon nanotubes (SWNTs) can be either metallic or semiconducting. Thus far, the production of SWNTs, irrespective of synthesis methods, still yields a mixture of both types, with the metallic type being prevalent. However, semiconducting-type SWNTs are needed for carbon nanotube field-effect transistors (CNT-FETs) as well as many sensors. This is because only the semiconducting-type SWNTs can be effectively modulated by the gate voltage. In contrast, the lack of field effect in metallic-type SWNTs adversely impacts their applications in high-performance electronic devices. In this study, we demonstrate for the first time a novel plasma treatment method that allows us to convert metallic-type carbon nanotubes to semi conducting-type CNT-FETs. On the basis of our experimental results, we believe that the ion bombardment during Ar plasma treatment attacks both metallic- and semiconducting-type nanotubes; however, the metallic-type carbon nanotubes are more vulnerable to the attack than those of the semiconducting type, and are subsequently transformed into the latter type.
Prospect of cobalt-mix-tetraethoxysilane method on localized lateral growth of carbon nanotubes for both p- and n-type field effect transistors
(2006-09-01)
Chen, Bae-Horng
;
Lin, Horng-Chih
;
Huang, Tiao-Yuan
;
Wei, Jeng-Hua
;
Hwang, Chien-Liang
To apply carbon nanotubes (CNTs) to nanoelectronics, researchers must effectively control the placement and manipulation of massive numbers of CNTs. In this work, we demonstrate a precise growth of single-walled carbon nanotubes (SWNT) on preassigned locations with only cobalt as catalyst. This is in contrast to the laborious and time-consuming physical manipulation of numerous nanotubes one at a time used in the conventional approach. Laterally grown CNTs were accomplished in preassigned areas using an integrated circuit compatible process in this study. In order to synthesize SWNT as the channel of a field effect transistor (FET), the cobalt-mix-tetraethoxysilane (CMT) solution and catalytic chemical vapor deposition were used. The CMT solution has the unique property of well dispersing the cobalt catalyst and uniformly embedding it in predetermined locations after the CMT solution has solidified. Our results show that laterally grown bundled-CNTs could be formed in atmospheric chemical vapor deposit ion with ethanol, by properly controlling the temperature of process, the process time, and the hydrogen reduction time. Since our bundled-CNTs were exposed to the air, all the as-grown CNT-FETs we manufactured exhibit p-type characteristics. Furthermore, we also demonstrate air-stable n-type CNT-FETs successfully without resorting to any additional and complicated annealing process by simply depositing a silicon nitride film on the as-grown p-type devices by plasma enhanced (PECVD) at 390 degrees C. The use of prepatterned catalyst islands, CVD method, and flexibility of simultaneously manufacturing both n- and p-type CNT-FETs may open a new era for applications of CNT-based nanoelectronics. (c) 2006 American Vacuum Society.