54 제23회 한국반도체학술대회

Ink-jet printed ambipolar transistors and inverters based on semiconducting carbon nanotubes with chemical doping technique

Juhee Lee, Bongsik Choi, Jinsu Yoon, Minsu Jeon, Yongwoo Lee, Jungmin Han, Jieun Lee, Dong Myong Kim, Dae Hwan Kim, and Sung-Jin Choia)

School of EE, Kookmin University, Seoul 136-702, Korea, E-mail : a)sjchoiee@kookmin.ac.kr

Carbon nanotubes have attracted extensive interests in electronic device applications because of high carrier mobility, excellent mechanical flexibility, and solution-based processability at room temperature. To efficiently fabricate various circuits based on carbon nanotube transistors, recently CMOS-like circuits consisting of ambipolar carbon nanotube transistors have received significant attentions due to their ease of fabrication and adaptiveness of more circuit design [1]. In this work, we demonstrate the ink-jet printed ambipolar transistors based on pre-separated, semiconducting carbon nanotube network as a channel by employing solution-based chemical doping technique with polyethyleneimine (PEI). The PEI has been reported as efficient electron dopants that exhibit stability in air and the adsorbed PEI on carbon nanotubes can readily overcome p-doping effects by oxygen molecules and have the electron-donating ability of amine groups in polymer [2]. Firstly, we present a solution-based doping technique for converting ink-jet printed p-type semiconducting carbon nanotube network transistors into ambipolar transistors by coating PEI on top surface of devices. Secondly, the electrical performance of ink-jet printed PEI coated ambipolar carbon nanotube network transistors is characterized by controlling the polyethyleneimine (PEI) concentration. Finally, the logic inverter consisting of two identical ambipolar carbon nanotube transistors is also demonstrated with a gain of 10 and power dissipation of 1.410-5 at operating voltage of 10 V. We expect that the concept presented here will be benefitial for development of various future electronic applications.

Fig 1. (a) Schematic of ink-jet printed, ambipolar carbon nanotube network transistor with PEI coating. (b) Transfer characteristics and (c) on-state currents before and after PEI coating on carbon nanotube network transistors. (d) Voltage transfer characteristics of inverter with two idential ambipolar carbon nanotube network transistors and circuit diagram (inset).

[1] W. J. Yu, et al., Nano Lett. 9, 4 (2009) [2] M. Shim, et al., J. Am. Chem. Soc. 123, 46 (2001) Acknowledgement: National research foundation of Korea (Grant 2013R1A1A1057870)

Alignment of Unpurified, Solution-Processed Single Walled Carbon Nanotubes via Dielectropherosis and Its Purification Scheme

Geun Woo Baek, Yoon Gy Hong , In Jae Yim, Hyeun Woo Kim, You-Beom Lee, Jae Hyeon Ryu, Gi Taek Yu,

and Sung Hun Jin* Department of Electronic Engineering, Incheon National University, Incheon 406-772, Korea

Tel: 82-32-835-8865 E-mail : shjin@inu.ac.kr

As silicon transistors approach to the physical limit of a few nanometer, single walled carbon nanotubes

have been still regarded as one of viable options for the ultra-scaled transistors with sub 10 nm channel length

because of their high saturation velocity and intrinsic thinness of one nanometer dimension which enables to

have a superior electrostatic control. However, placement and purity (>99.999%) control of SWNTs including

wafer scaled-integration with high density (>200/ μm) have been still long standing problems in this field.

Particularly wafer-scaled integration of SWNTs with utra-high purity via low cost based process scheme is

dramatically required for the first pavement of being open to the real application including low power

radio-frequency circuits, nanoscale digital switching devices, and chemical sensors with unique functionality.

Here we reported solution processed alignment schemes via [1] dielectropherosis which is fully

compatible with [2] thermo-capillarity enabled purification (TcEP) with wafer-sized scalability. In this study, for

the low-cost and high yield of purification, we proposed to use solution processed single walled carbon

nanotubes with moderate purity (>80%) as it is synthesized by using the novel catalyst based chemical vapor

deposition, which is immediately ready to be extended toward tons of manufacturability. One of key results as

shown in Fig. 1 indicates that the controllability of SWNT density and its alignment by using unpurified,

solution processed SWNTs via dielectropherosis and its initial transfer curves for aligned SWNT FETs before

TcEP, which hint SWNTs as they are synthesized have high portion of semiconducting nanotubes.

30 20 10 0 -10 -20 -3010

-12

10-10

10-8

10-6

10-4

10-2

100

W/L=100/30m, VDS

=-1V

-I DS (A

)

VGS

(V)

1000:1 7000:1

(a) (c)(b)

Fig 1. Scanning electron microscope (SEM) images for aligned SWNTs via dielectropherosis by using unpurified, solution

processed single walled carbon nanotubes with different concentration of (a) 1000:1 and (b) 7,000:1, respectively. (c) Transfer

characteristics for aligned SWNTs FETs right after dielectropherosis with split concentration.

[1] Shashank Shekhar et al, ACS Nano. 5, 1739 (2011).

[2] Sung Hun Jin and S. N. Dunham et al, Nature Nanotechnology, 8, 347–355 (2013)

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