Phonon engineering in graphene materials
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2024-02-25 21:51
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NIKA, Denis, BALANDIN, Alexander A.. Phonon engineering in graphene materials. In: Materials Science and Condensed Matter Physics, Ed. 8-th Edition, 12-16 septembrie 2016, Chişinău. Chişinău: Institutul de Fizică Aplicată, 2016, Editia 8, p. 208. ISBN 978-9975-9787-1-2.
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Materials Science and Condensed Matter Physics
Editia 8, 2016
Conferința "International Conference on Materials Science and Condensed Matter Physics"
8-th Edition, Chişinău, Moldova, 12-16 septembrie 2016

Phonon engineering in graphene materials


Pag. 208-208

Nika Denis1, Balandin Alexander A.2
 
1 Moldova State University,
2 Universitatea din California - Riverside, Nano-Device Laboratory
 
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Disponibil în IBN: 31 iulie 2019


Rezumat

Acoustic phonons are the main heat carriers in carbon materials [1-2]. Although graphite reveals many metal characteristics, its heat transport is dominated by phonons owing the exceptionally strong sp2 covalent bonding of its lattice. The thermal conductivity of various allotropes of carbon span an extraordinary large range – of over five orders of magnitude – from ~0.01 Wm-1K-1 in amorphous carbon to above 2000 Wm-1K-1 in diamond or graphite at room temperature (RT) [1]. In 2007, the first measurements of the thermal conductivity of graphene carried out by Prof. A. Balandin’s group at UC Riverside revealed unusually high values of thermal conductivity κ~3000 – 5000 Wm-1K-1 at RT [1-2]. The values measured for the high-quality large suspended graphene samples (length above 10 µm) were exceeding those for basal planes of graphite [1-2]. The experimental observation was explained theoretically by the specifics of the two-dimensional (2D) phonon transport [2]. The low-energy acoustic phonons in graphene, which make substantial contribution to heat conduction, weakly participate in anharmonic scattering and have extraordinary large mean-free-path. Several independent studies, which followed, also utilized the Raman optothermal technique but modified it via addition of a power meter under the suspended portion of graphene [3-5]. It was found that the thermal conductivity of suspended high-quality chemical vapor deposited graphene exceeded ~2500 Wm-1K-1 at 350 K, and it was as high as κ≈1400 Wm-1K1 at 500 K [3]. Another Raman optothermal study with the suspended graphene found the thermal conductivity in the range from ~1500 to ~5000 Wm-1K-1 [4]. The thermal conductivity of fully supported graphene is smaller. The measurements for exfoliated graphene on SiO2/Si revealed inplane κ≈600 Wm-1K-1 near RT [5]. Despite the noted data scatter in the reported experimental values of the thermal conductivity of graphene, one can conclude that it is very large compared to that for bulk silicon (κ=145 Wm-1K-1 at RT) or bulk copper (κ=400 Wm-1K-1 at RT) – important materials for electronic applications. The differences in κ of graphene can be attributed to variations in the graphene sample lateral sizes (length and width), thickness non-uniformity due to the mixing between single-layer and few-layer graphene, material quality (e.g. defect concentration and surface contaminations), grain size and orientation, as well as strain distributions. The latter make graphene an ideal material for phonon engineering.   In this talk we will review recent results on thermal transport in graphene-based materials. The large scattering in reported thermal conductivity values of single layer graphene will be discussed. The unusual thermal properties of twisted graphene [6], graphene laminate [7] and reduced graphene oxide [8] will be also explained.   Acknowledgements: One author (DLN) acknowledges the financial supprot from the Moldova Goverment through the institutional project 15.817.02.29F.