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Research Papers: Micro/Nanoscale Heat Transfer

Thermal Conductivity Measurement of Graphene Exfoliated on Silicon Dioxide

[+] Author and Article Information
Jae Hun Seol, Arden L. Moore

Department of Mechanical Engineering, University of Texas at Austin, Austin, TX 78712

Li Shi1

Department of Mechanical Engineering, University of Texas at Austin, Austin, TX 78712lishi@mail.utexas.edu

Insun Jo, Zhen Yao

Department of Physics, University of Texas at Austin, Austin, TX 78712

1

Corresponding author.

J. Heat Transfer 133(2), 022403 (Nov 03, 2010) (7 pages) doi:10.1115/1.4002608 History: Received April 29, 2010; Revised August 27, 2010; Published November 03, 2010; Online November 03, 2010

We have developed a nanofabricated resistance thermometer device to measure the thermal conductivity of graphene monolayers exfoliated onto silicon dioxide. The measurement results show that the thermal conductivity of the supported graphene is approximately 600W/mK at room temperature. While this value is lower than the reported basal plane values for graphite and suspended graphene because of phonon leakage across the graphene-support interface, it is still considerably higher than the values for common thin film electronic materials. Here, we present a detailed discussion of the design and fabrication of the measurement device. Analytical and numerical heat transfer solutions are developed to evaluate the accuracy and uncertainty of this method for thermal conductivity measurement of high-thermal conductivity ultrathin films.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

((a) and (b)) Layout schematic of the measurement device that consists of an Au/Cr layer (white), 300-nm-thick SiO2 layer (gray), and an etching pit (black) under the Au/Cr/SiO2 beams and the central graphene/SiO2 beam. (c) Thermal circuit of the measurement device. T1,m, T2,m, T3,m, and T4,m are the midpoint temperatures of RT1, RT2, RT3, and RT4, respectively, as indicated in (b). T0 is the substrate temperature. Rs, Rb, and R0 are the thermal resistances of the central graphene/SiO2 beam, each RT line including the supporting SiO2 beam, and the SiO2 joint between the adjacent straight and U-shaped RT lines, respectively. Q1 is the heat conducted from the self heated RT1 into the other three RT lines. Q2, Q3, and Q4 are the heat conducted from RT2, RT3, and RT4 into the substrate, respectively. The scale bars are 20 μm and 5 μm in (a) and (b), respectively.

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Figure 2

Schematic diagram of the fabrication process. (a) A graphene flake was exfoliated on a 300-nm-thick SiO2 film thermally grown on a Si wafer. (b) Au/Cr RT lines were patterned with the use of EBL and metal lift-off. (c) The graphene was patterned using EBL and oxygen plasma etching so that only the part of graphene flake between the two inner straight RTs was left after patterning. (d) Windows in the SiO2 layer were patterned and etched to form Au/Cr/SiO2 beams and graphene/SiO2 beams. (e) The device was suspended by etching the underlying silicon substrate in a TMAH solution. All schematics are not to scale.

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Figure 3

SEM images of (a) the measurement device, (b) the central beam, and (c) the supported graphene ribbon near one straight Au/Cr RT line. The scale bars are 10 μm, 2 μm, and 1 μm in (a), (b), and (c), respectively.

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Figure 4

Measured resistance increases ΔRj (for j=1 to 4) of RT1,RT2, RT3, and RT4 as a function of heating current in RT1 when the sample stage temperature was kept at 325 K

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Figure 5

Measured low-biased electrical resistances of RT1 and RT3 in RT1 as a function of the sample stage temperature. Lines are linear fits to the measurement data.

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Figure 6

Measured (a) average and (b) midpoint temperatures of RT1, RT2, RT3, and RT4 at T0=325 K as function of the heating power in RT1

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Figure 7

Measured thermal conductance of the central beam before and after the graphene on top of the central SiO2 beam was etched with the difference found as the thermal conductance of the graphene

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Figure 8

Temperature distribution (a) on the entire device and (b) near the central graphene/SiO2 beam obtained from numerical heat transfer analysis of the device

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Figure 9

Thermal conductivity of the supported graphene as a function of temperature

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Figure 10

Thermal conductivity of the central SiO2 beam as a function of temperature. The error bars of the measurement results are smaller than the size of the symbols. Shown for comparison is the thermal conductivity for thermally grown SiO2 reported by Cahill (28).

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