Electrical evidence for the encapsulation of ${\text{C}}_{60}$ inside a carbon nanotube: Random telegraph signal and hysteric current--voltage characteristics

Electrical evidence for the encapsulation of $C_{60}$ inside a carbon nanotube: Random telegraph signal and hysteric current–voltage characteristics

Han Young Yu, Dong Su Lee, Ursula Dettlaff-Weglikowska, Siegmar Roth, and Yung Woo Park

Phys. Rev. B 78, 155415 – Published 10 October 2008

Abstract

We present electrical evidence for the encapsulation of $C_{60}$ ’s inside a carbon nanotube, random telegraph signals (RTSs), and hysteric current–voltage characteristics. RTSs are shown only at voltages higher than a critical voltage. We suggest that the origin of the RTSs is ascribed to the instability of the quantum harmonic oscillations of $C_{60}$ ’s. RTSs are smeared out at a temperature which is well correlated with the energy level of the vibrational quantum mediated by the van der Waals binding between the carbon nanotube and $C_{60}$ ’s. In addition, hysteric behavior in cyclic current–voltage characteristics is explained by the longitudinal motion and resettlement of the $C_{60}$ ’s with the modulation of the size of the quantum dot mediated by the $C_{60}$ insertion.

Received 20 May 2008

DOI:https://doi.org/10.1103/PhysRevB.78.155415

Authors & Affiliations

Han Young Yu^1,2, Dong Su Lee^1,3, Ursula Dettlaff-Weglikowska³, Siegmar Roth³, and Yung Woo Park^1,*

¹School of Physics, Seoul National University, Seoul 151-747, Republic of Korea and Nano Systems Institute–National Core Research Center, Seoul National University, Seoul 151-747, Republic of Korea
²Electronics and Telecommunications Research Institute, Daejeon 305-700, Republic of Korea
³Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany

^*Author to whom correspondence should be addressed. ywpark@phya.snu.ac.kr

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Vol. 78, Iss. 15 — 15 October 2008

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Figure 1
(Color online) (a) A representative AFM image of a $C_{60}$ device. (b) A schematic diagram of the $C_{60}$ device circuit. A $C_{60}$ peapod is deposited on top of the electrodes, a source electrode is connected to a voltage source and a current meter, and highly $n$ -doped bottom silicon is connected to a gate.Reuse & Permissions
Figure 2
(Color online) (a) Bias voltage dependence of the RTSs with applied voltages from 0.9 to 1.4 V at $T = 1.8 K$ . (b) A plot of the averaged current levels deduced from the bias-voltage-dependent RTSs and an $I - V$ characteristic at $T = 1.8 K$ : the threshold voltage $V_{th}$ (0.51 V) and the critical voltage $V_{C}$ , where the differential conductance shows peaks and discrete current levels appear, respectively. Upper inset: An $I - V$ characteristic with applied voltages ranging from $- 2$ to 2 V at $T = 1.8 K$ . Lower inset: Differential conductance curve. Comparing the behavior of $I - V$ characteristic (line) to the discrete current levels of the RTSs (diamonds), the fluctuations in the $I - V$ curve are well correlated with the deviations of the discrete RTS levels.Reuse & Permissions
Figure 3
(Color online) Left: Schematic diagram of the variation of the binding potential $U$ with respect to the distance $r$ from the inner wall of carbon nanotube to the surface of $C_{60}$ . Right: Schematic diagram of the structure of a peapod with a single $C_{60}$ , the electronic band diagram for the peapod quantum dot, and the resulting subband from the quantum harmonic oscillations (the energy of $h$ ) of $C_{60}$ near the stable position in a direction perpendicular to the tube axis. A: Pure carbon nanotube region; B: $C_{60}$ inserted region in a peapod; $E_{1}$ and $E_{2}$ : The energy states mediated by the peapod quantum dot.Reuse & Permissions
Figure 4
(Color online) (a) Temperature-dependent RTSs with a source-drain voltage of 1.3 V. (a) Discrete current levels appear at temperatures ranging from 1.8 to 100 K. (b) Current fluctuations without quantized levels at temperatures from 200 to 300 K.Reuse & Permissions
Figure 5
(Color online) Plot of the conductance in the discrete RTS levels as a function of temperature from 1.8 to 300 K at $V_{SD} = 1.3 V$ . Inset shows RTS levels above critical temperature of 150 K.Reuse & Permissions
Figure 6
(Color online) (a) Cyclic $I - V$ characteristics of a $C_{60}$ peapod device at $T = 1.8 K$ . The induced current was measured under the following sequence of voltage sweeps: up1, down1, up2, and down2. (b) Differential conductance curves to the applied source-drain voltage. Arrows indicate conductance peaks at each differential conductance.Reuse & Permissions

Physical Review B

covering condensed matter and materials physics

Electrical evidence for the encapsulation of $C_{60}$ inside a carbon nanotube: Random telegraph signal and hysteric current–voltage characteristics

Han Young Yu, Dong Su Lee, Ursula Dettlaff-Weglikowska, Siegmar Roth, and Yung Woo Park

Phys. Rev. B 78, 155415 – Published 10 October 2008

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Physical Review B

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Electrical evidence for the encapsulation of C60 inside a carbon nanotube: Random telegraph signal and hysteric current–voltage characteristics

Han Young Yu, Dong Su Lee, Ursula Dettlaff-Weglikowska, Siegmar Roth, and Yung Woo Park

Phys. Rev. B 78, 155415 – Published 10 October 2008

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Electrical evidence for the encapsulation of $C_{60}$ inside a carbon nanotube: Random telegraph signal and hysteric current–voltage characteristics