Lim, Gyumin Kihm, Kenneth David Kim, Hong Goo Lee, Woorim Lee, Woomin Pyun, Kyung Rok Cheon, Sosan Lee, Phillip Min, Jin Young Ko, Seung Hwan 2024-01-19T22:31:17Z 2024-01-19T22:31:17Z 2021-09-03 2018-07 2079-4991 https://pubs.kist.re.kr/handle/201004/121210 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 mu m, 2.2 mu m, and 0.5 mu m was 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 sigma-, S, and k. Electrical conductivity (sigma) 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 (V-G). Mobility (mu) values of 529, 459, and 314 cm(2)/V.s for holes and 1042, 745, and 490 cm(2)/V.s for electrons for the three grain sizes of 4.1 mu m, 2.2 mu m, and 0.5 mu m, respectively, were obtained from the slopes of the measured sigma- vs. V-G 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 mu m to 0.5 mu m. English MDPI CHEMICAL-VAPOR-DEPOSITION SINGLE-CRYSTAL GRAPHENE RAMAN-SPECTROSCOPY ELECTRICAL-TRANSPORT GROWTH CU FILMS Enhanced Thermoelectric Conversion Efficiency of CVD Graphene with Reduced Grain Sizes Article 10.3390/nano8070557 1 NANOMATERIALS, v.8, no.7 NANOMATERIALS 8 7 scie scopus 000442523100108 2-s2.0-85050747531 Chemistry, Multidisciplinary Nanoscience & Nanotechnology Materials Science, Multidisciplinary Physics, Applied Chemistry Science & Technology - Other Topics Materials Science Physics Article CHEMICAL-VAPOR-DEPOSITION SINGLE-CRYSTAL GRAPHENE RAMAN-SPECTROSCOPY ELECTRICAL-TRANSPORT GROWTH CU FILMS thermoelectric conversion efficiency CVD graphene grain sizes FET 4-point measurements electrical conductivity Seebeck coefficient