In-Plane Thermal Conductivity of Polycrystalline Chemical Vapor Deposition Graphene with Controlled Grain Sizes

Abstract

Manipulation of the chemical vapor deposition graphene synthesis conditions, such as operating P, T, heating/cooling time intervals, and precursor gas concentration ratios (CH/H), allowed for synthesis of polycrystalline single-layered graphene with controlled grain sizes. The graphene samples were then suspended on 8 μm diameter patterned holes on a silicon-nitride (SiN) substrate, and the in-plane thermal conductivities k(T) for 320 K < T < 510 K were measured to be 2660-1230, 1890-1020, and 680-340 W/m·K for average grain sizes of 4.1, 2.2, and 0.5 μm, respectively, using an opto-thermal Raman technique. Fitting of these data by a simple linear chain model of polycrystalline thermal transport determined k = 5500-1980 W/m·K for single-crystal graphene for the same temperature range above; thus, significant reduction of k was achieved when the grain size was decreased from infinite down to 0.5 μm. Furthermore, detailed elaborations were performed to assess the measurement reliability of k by addressing the hole-edge boundary condition, and the air-convection/radiation losses from the graphene surface.

Synthesis of in situ N‐, S‐, and B‐doped few‐layer graphene by chemical vapor deposition technique and their superior glucose electrooxidation activity

“…[36][37][38] Single-layer graphene was first obtained by Novoselov et al, and they were awarded by the Physics Nobel Prize in 2010. [45][46][47] CVD synthesis method of graphene is advantageous in several aspects with its capability for large-area, high-quality synthesis as well as layer controllability compared with other methods. [45][46][47] CVD synthesis method of graphene is advantageous in several aspects with its capability for large-area, high-quality synthesis as well as layer controllability compared with other methods.…”

“…[39][40][41] Graphene synthesis has been studied via various methods such as epitaxial growth on SiC, 42 mechanical exfoliation, 43 reduction of graphene oxide, 44 and chemical vapor deposition (CVD). [45][46][47] CVD synthesis method of graphene is advantageous in several aspects with its capability for large-area, high-quality synthesis as well as layer controllability compared with other methods. CVD has exposed as the leading growth method that is naturally scalable for large area film production.…”

Few‐layer graphene coated on indium tin oxide electrodes prepared by chemical vapor deposition and their enhanced glucose electrooxidation activity

“…Graphene production techniques have been known mechanical cleavage, chemical peeling, epitaxial growth, Hummers method, sublimation of 4HSiC, electrochemical reduction, and CVD . Among these methods, CVD is layer system formed on the surface of a solid material and it is a short‐time and simple method …”

“…[37][38][39][40] Among these methods, CVD is layer system formed on the surface of a solid material and it is a shorttime and simple method. [40][41][42] Vaporous carrier gas exposes to the surface of a material via heating in a closed container, mostly used in graphene synthesis. CVD is one of the best methods in the production of graphene in a wide range of structures and diameters.…”

Interfacial Thermal Contact Conductance inside the Graphene–Bi2Te3 Heterostructure

“…Raman thermometry is considered to be a well‐established technique for measuring thermal conductivities in 2D materials based on the Raman peak shift correlations with the sample surface temperature . While Raman thermometry essentially determines a single unknown at a time, it can be extended to determine two unknowns by repeating experiments using two different objective lenses providing different laser incidence . For instance, conducting experiments using 20× and 100× objective lenses can create two independent Raman peak‐temperature correlations, which allows for the simultaneous determination of two unknowns, such as graphene conductivity and graphene/Bi 2 Te 3 contact conductance, if the Bi 2 Te 3 conductivity is already known.…”