Preprint Article Version 1 This version is not peer-reviewed

Enhanced Thermoelectric Conversion Efficiency of CVD Graphene with Reduced Grain Sizes

Version 1 : Received: 23 June 2018 / Approved: 24 June 2018 / Online: 24 June 2018 (11:32:58 CEST)

A peer-reviewed article of this Preprint also exists.

Lim, G.; Kihm, K.D.; Kim, H.G.; Lee, W.; Lee, W.; Pyun, K.R.; Cheon, S.; Lee, P.; Min, J.Y.; Ko, S.H. Enhanced Thermoelectric Conversion Efficiency of CVD Graphene with Reduced Grain Sizes. Nanomaterials 2018, 8, 557. Lim, G.; Kihm, K.D.; Kim, H.G.; Lee, W.; Lee, W.; Pyun, K.R.; Cheon, S.; Lee, P.; Min, J.Y.; Ko, S.H. Enhanced Thermoelectric Conversion Efficiency of CVD Graphene with Reduced Grain Sizes. Nanomaterials 2018, 8, 557.

Journal reference: Nanomaterials 2018, 8, 557
DOI: 10.3390/nano8070557

Abstract

The grain size of CVD (Chemical Vapor Deposition) graphene was controlled by changing the precursor gas flow rates, operation temperature, and chamber pressure. Graphene of average grain sizes of 4.1 µm, 2.2 µm, and 0.5 µm were synthesized in high quality and full coverage. The possibility to tailor the thermoelectric conversion characteristics of graphene has been exhibited by examining the grain size effect on the three elementary thermal and electrical properties of σ, S, and k. Electrical conductivity (σ) and Seebeck coefficients (S) were measured in a vacuum for supported graphene on SiO2/Si FET (Field Effect Transistor) substrates so that the charge carrier density could be changed by applying a gate voltage (VG). Mobility (µ) values of 529~1042, 459~745, and 314~490 cm2/V·s for the three grain sizes of 4.1 µm, 2.2 µm, and 0.5 µm, respectively, were obtained from the slopes of the measured σ vs. VG graphs. The power factor (PF), the electrical portion of the thermoelectric figure of merit (ZT), decreased by about one half as the grain size was decreased, while the thermal conductivity (k) decreased by one quarter for the same grain decrease. Finally, the resulting ZT increased more than two times when the grain size was reduced from 4.1 µm to 0.5 µm.

Subject Areas

thermoelectric conversion efficiency; CVD graphene; grain sizes; FET 4-point measurements; electrical conductivity; seebeck coefficient

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