Influence of roughness on near-field heat transfer between two plates

Biehs, Svend‐Age; Greffet, Jean‐Jacques

doi:10.1103/physrevb.82.245410

Cited by 39 publications

(24 citation statements)

References 38 publications

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“…The enhancement of HT in the near-field regime (generally denoting separations small compared to the thermal wavelength, which is roughly 8 microns at room temperature) has only recently been verified experimentally [5,6]. Theoretically, HT has been considered for a limited number of shapes: Parallel plates [2,3,7,8], a dipole or sphere in front a plate [9][10][11], two dipoles or spheres [9,12,13], and for a cone and a plate [14]. The scattering formalism has been successfully exploited [10,[15][16][17][18] in this context.…”

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Small distance expansion for radiative heat transfer between curved objects

Golyk¹,

Krüger²,

McCauley³

et al. 2013

EPL

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-We develop a small distance expansion for the radiative heat transfer between gently curved objects, in terms of the ratio of distance to radius of curvature. A gradient expansion allows us to go beyond the lowest order proximity transfer approximation. The range of validity of such expansion depends on temperature as well as material properties. Generally, the expansion converges faster for the derivative of the transfer than for the transfer itself, which we use by introducing a near-field adjusted plot. For the case of a sphere and a plate, the logarithmic correction to the leading term has a very small prefactor for all materials investigated.More than 40 years ago Van Hove and Polder used Rytov's fluctuational electrodynamics [1] to predict that the radiative heat transfer (HT) between objects separated by a vacuum gap can exceed the blackbody limit [2]. This is due to evanescent electromagnetic fields decaying exponentially into the vacuum. HT due to evanescent waves has also attracted a lot of interest due to its connection with scanning tunnelling microscopy, and scanning thermal microscopy under ultra-high vacuum conditions [3,4]. The enhancement of HT in the near-field regime (generally denoting separations small compared to the thermal wavelength, which is roughly 8 microns at room temperature) has only recently been verified experimentally [5,6]. Theoretically, HT has been considered for a limited number of shapes: Parallel plates [2,3,7,8], a dipole or sphere in front a plate [9][10][11], two dipoles or spheres [9,12,13], and for a cone and a plate [14]. The scattering formalism has been successfully exploited [10,[15][16][17][18] in this context. Although powerful numerical techniques [14,19] exist for arbitrary geometries, analytical computations are limited to planar, cylindrical and spherical cases [18]. Alternatively, the HT between closely spaced curved objects can be computed by use of the proximity transfer approximation (PTA) [10,11,20], which exploits an approach that has been extensively used in the context of fluctuation induced forces [21] (referred to as proximity force approximation): The HT between two parallel plates (per unit area), H pp (S), for separation S is averaged over one of the (projected) curved surfaces. PTA is generally assumed to hold asymptotically for small separations, however no rigorous derivation appears available in the literature.Here we develop a gradient expansion for HT between closely spaced objects, which enables to rigorously justify PTA and to quantify corrections to it in the limit of small separation. This method, which has been proposed for Casimir forces [22][23][24], exploits the mapping of coefficients of a perturbative expansion on one side and a gradient expansion on the other. We carefully explore the limitations and subtleties of this method in the case of HT and propose a near-field adjusted plot that overcomes the possibly slow convergence of the expansion.Consider two non-magnetic objects with dielectric permittivities ǫ 1 (ω) and ...

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“…(4) is an expansion in the ratio of separation to radius of curvature of the surface. The coefficient β ω (S) is obtained from the perturbative expansion [8] …”

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Small distance expansion for radiative heat transfer between curved objects

Golyk¹,

Krüger²,

McCauley³

et al. 2013

EPL

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“…It has been theoretically predicted that NFRHT can be controlled using nanoporous materials, 5 thin films, 6,7 and graphene sheets, [8][9][10][11] or by adjusting the material temperature, 12 surface roughness, 13 and metal-insulator transition. 14 In contrast to a large number of theoretical studies, there exist few experiments that demonstrate the tuning of NFRHT.…”

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Tuning near field radiation by doped silicon

Shi

Liu

et al. 2013

Applied Physics Letters

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In this letter, we demonstrate theoretically and experimentally that bulk silicon can be employed to overcome the challenge of tuning near field radiation. Theoretical calculation shows that the nanoscale radiation between bulk silicon and silicon dioxide can be tuned by changing the carrier concentration of silicon. Near field radiation measurements are carried out on multiple bulk silicon samples with different doping concentrations. The measured near field conductance agrees well with theoretical predictions, which demonstrates a tuning range from 2 nW/K to 6 nW/K at a gap of ∼60 nm.

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“…For structured as well as for rough surfaces (Biehs et al (2010c;d;; ) the LDOS can be calculated pertubatively by using for example the perturbation approach of (Greffet (1988)) if the height differences of the surface profile are the smallest length scales and in particular smaller than the thermal wavelength (Henkel and Sandoghdar (1998)). This allows for comparision of the NSThM data with theory, i.e., with the numerically evaluated LDOS D M (ω th , r tip ).…”

Section: Thermal Imagingmentioning

confidence: 99%