Thermal transport across graphene step junctions

Rojo, Miguel Muñoz; Li, Zuanyi; Sievers, C.; Bornstein, Alex; Yalon, Eilam; Vaziri, Sam; Bae, Myung‐Ho; Xiong, Feng; Donadio, Davide; Pop, Eric

doi:10.1088/2053-1583/aae7ea

Cited by 17 publications

(8 citation statements)

References 43 publications

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“…This is attributed to the electric field created by surface dipoles in the oxide being screened by the bottom layer and consequently not affecting charge carriers in the top layer, as previously indirectly observed [28,29]. In addition, this observation provides evidence that the two graphene layers are thermally largely decoupled [30]. Assuming charge puddles are present in the bottom layer as they are in the SLG area, any temperature differential caused by the tip should cause a thermovoltage signal, which is not observed in our experiment.…”

Section: Single-layer/bilayer Junctionsupporting

confidence: 78%

Direct Mapping of Local Seebeck Coefficient in 2D Material Nanostructures via Scanning Thermal Gate Microscopy

Harzheim,

Evangeli,

Kolosov

et al. 2020

Preprint

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Local variations in the Seebeck coecient in low-dimensional materials-based nanostructures and devices play a major role in their thermoelectric performance. Unfortunately, currently most thermoelectric measurements probe the aggregate characteristics of the device as a whole, failing to observe the effects of the local variations and internal structure. Such variations can be caused by local defects, geometry, electrical contacts or interfaces and often substantially influence thermoelectric properties, most profoundly in two-dimensional (2D) materials. Here, we use Scanning Thermal Gate Microscopy (STGM), a non-invasive method not requiring an electrical contact between the nanoscale tip and the probed sample, to obtain nanoscale resolution 2D maps of the thermovoltage in graphene samples. We investigate a junction formed between single-layer and bilayer graphene and identify the impact of internal strain and Fermi level pinning by the contacts using a deconvolution method to directly map the local Seebeck coefficient. The new approach paves the way for an in-depth understanding of thermoelectric behaviour and phenomena in 2D materials nanostructures and devices.

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Section: Single-layer/bilayer Junctionsupporting

confidence: 78%

Direct Mapping of Local Seebeck Coefficient in 2D Material Nanostructures via Scanning Thermal Gate Microscopy

Harzheim,

Evangeli,

Kolosov

et al. 2020

Preprint

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“…G H/L may be replaced by the heat currents J H/L , provided that the temperature difference between the thermal reservoirs remains the same when the temperature bias is inverted. The above mentioned simulation works predict extremely high η, up to 350%, for carbon-based devices, but experimental measurements show much smaller thermal rectification, if any at all [70,72,73].…”

Section: F Thermal Rectification In Asymmetric Graphene-based Systemsmentioning

confidence: 99%

Influence of thermostatting on nonequilibrium molecular dynamics simulations of heat conduction in solids

Xiong

Sievers

et al. 2019

The Journal of Chemical Physics

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166

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Nonequilibrium molecular dynamics (NEMD) has been extensively used to study thermal transport at various length scales in many materials. In this method, two local thermostats at different temperatures are used to generate a nonequilibrium steady state with a constant heat flux. Conventionally, the thermal conductivity of a finite system is calculated as the ratio between the heat flux and the temperature gradient extracted from the linear part of the temperature profile away from the local thermostats. Here we show that, with a proper choice of the thermostat, the nonlinear part of the temperature profile should actually not be excluded in thermal transport calculations. We compare NEMD results against those from the atomistic Green's function method in the ballistic regime, and those from the homogeneous nonequilibrium molecular dynamics method in the ballistic-to-diffusive regime. These comparisons suggest that in all the transport regimes, one should directly calculate the thermal conductance from the temperature difference between the heat source and sink and, if needed, convert it to the thermal conductivity by multiplying it with the system length. Furthermore, we find that the Langevin thermostat outperforms the Nosé-Hoover (chain) thermostat in NEMD simulations because of its stochastic and local nature. We show that this is particularly important for studying asymmetric carbon-based nanostructures, for which the Nosé-Hoover thermostat can produce artifacts leading to unphysical thermal rectification. Our findings are important to obtain correct results from molecular dynamics simulations of nanoscale heat transport as the accuracy of the interatomic potentials is rapidly improving. :1905.11024v1 [cond-mat.mes-hall] arXiv

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“…Muñoz Rojo et al. [ 106 ] investigated the potential thermal rectification properties of step graphene junctions, defined as steps between regions with different number of graphene layers. The heat flow across graphene junctions from monolayer to bilayer graphene, as well as bilayer to four‐layer graphene, were measured for the first time in both directions (forward vs reverse).…”

Section: Thermal Diodesmentioning

confidence: 99%

Solid‐State Thermal Control Devices

Swoboda

Klinar

Yalamarthy

et al. 2020

Adv Elect Materials

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Over the past decade, solid‐state thermal control devices have emerged as potential candidates for enhanced thermal management and storage. They distinguish themselves from traditional passive thermal management devices in that their thermal properties have sharp, nonlinear dependencies on direction and operating temperature, and can lead to more efficient circuits and energy conversion systems than what is possible today. They also distinguish themselves from traditional active thermal management devices (e.g., fans) in that they have no moving parts and are compact and reliable. In this article, the recent progress in the four broad categories of solid‐state thermal control devices that are under active research is reviewed: diodes, switches, regulators, and transistors. For each class of device, the operation principle, material choices, as well as metrics to compare and contrast performance are discussed. New architectures that are explored theoretically, but not experimentally demonstrated, are also discussed.

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Thermal transport across graphene step junctions

Cited by 17 publications

References 43 publications

Direct Mapping of Local Seebeck Coefficient in 2D Material Nanostructures via Scanning Thermal Gate Microscopy

Direct Mapping of Local Seebeck Coefficient in 2D Material Nanostructures via Scanning Thermal Gate Microscopy

Influence of thermostatting on nonequilibrium molecular dynamics simulations of heat conduction in solids

Solid‐State Thermal Control Devices

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