Thermal transport in phononic crystals and the observation of coherent phonon scattering at room temperature

Alaie, Seyedhamidreza; Goettler, Drew F.; Su, Mehmet F.; Leseman, Zayd Chad; Reinke, Charles M.; El-Kady, Ihab F

doi:10.1038/ncomms8228

Cited by 155 publications

(177 citation statements)

References 36 publications

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“…6 On the other side, a recent work attempts to quantify the effect of coherence effects in periodic structures at room temperature. 7 In this study, the coherence regime is accounted for band-folding effects and a hybrid coherent/incoherent model was able to partially explain the remarkably low thermal conductivities obtained in their samples. It is clear, therefore, that the influence of phonon phase-conserving phenomena in such structures is still under debate.…”

Section: Introductionmentioning

confidence: 87%

Temperature-dependent thermal conductivity in silicon nanostructured materials studied by the Boltzmann transport equation

et al. 2016

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Nanostructured materials exhibit low thermal conductivity because of the additional scattering due to phonon-boundary interactions. As these interactions are highly sensitive to the mean free path (MFP) of phonons, MFP distributions in nanostructures can be dramatically distorted relative to bulk. Here we calculate the MFP distribution in periodic nanoporous Si for different temperatures, using the recently developed MFP-dependent Boltzmann Transport Equation. After analyzing the relative contribution of each phonon branch to thermal transport in nanoporous Si, we find that at room temperature optical phonons contribute 17% to heat transport, compared to 5% in bulk Si. Interestingly, we observe a constant thermal conductivity over the range 200 K < T < 300 K. We attribute this behavior to the ballistic transport of acoustic phonons with long intrinsic MFP and the temperature dependence of the heat capacity. Our findings, which are in qualitative agreement with the temperature trend of thermal conductivities measured in nanoporous Si-based systems, shed light on the origin of the reduction of thermal conductivity in nanostructured materials, and demonstrate the necessity of multiscale heat transport engineering, in which the bulk material and geometry are optimized concurrently.

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Section: Introductionmentioning

confidence: 87%

Temperature-dependent thermal conductivity in silicon nanostructured materials studied by the Boltzmann transport equation

et al. 2016

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“…For PnC's there is the question, whether the periodicity is still just an incoherent array of scatterers, or whether wave coherence can play a role and modify the phonon dispersion relations. 6 Most of the experimental studies so far have concentrated on thermal conductivity at intermediate-to-room temperatures, and studied either on 2D holey structures [7][8][9][10] or 1D superlattices. 11,12 At those temperatures, diffusive scattering is definitely still operational, 13,14 meaning that the effect of coherence is only partial, if existing at all.…”

Section: Introductionmentioning

confidence: 99%

Low temperature heat capacity of phononic crystal membranes

Puurtinen

Maasilta

2016

AIP Advances

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Phononic crystal (PnC) membranes are a promising solution to improve sensitivity of bolometric sensor devices operating at low temperatures. Previous work has concentrated only on tuning thermal conductance, but significant changes to the heat capacity are also expected due to the modification of the phonon modes. Here, we calculate the area-specific heat capacity for thin (37.5 - 300 nm) silicon and silicon nitride PnC membranes with cylindrical hole patterns of varying period, in the temperature range 1 - 350 mK. We compare the results to two- and three-dimensional Debye models, as the 3D Debye model is known to give an accurate estimate for the low-temperature heat capacity of a bulk sample. We found that thin PnC membranes do not obey the 3D Debye T3 law, nor the 2D T2 law, but have a weaker, approximately linear temperature dependence in the low temperature limit. We also found that depending on the design, the PnC patterning can either enhance or reduce the heat capacity compared to an unpatterned membrane of the same thickness. At temperatures below ∼ 100 mK, reducing the membrane thickness unintuitively increases the heat capacity for all samples studied. These observations can have significance when designing calorimetric detectors, as heat capacity is a critical parameter for the speed and sensitivity of a device.

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“…Two-dimensional phononic crystals (PnC) are not only useful for controlling acoustic and elastic waves [1], but have recently been shown to offer great possibilities for engineering thermal conduction, even at room temperatures [2][3][4][5], but most notably at ultra-low temperatures below 1 K [6]. At room temperature, the mechanisms for thermal conductivity reduction in PnCs are still somewhat controversial [4,5,7,8], in particular there is a debate whether coherent effects, as already seen in 1D superlattices [9], play a role or not.…”

Section: Introductionmentioning

confidence: 99%

“…At room temperature, the mechanisms for thermal conductivity reduction in PnCs are still somewhat controversial [4,5,7,8], in particular there is a debate whether coherent effects, as already seen in 1D superlattices [9], play a role or not. At low temperatures, the dominant thermal wavelengths of phonons can reach the micron length scale [6]; moreover, most bulk scattering mechanisms die out.…”

Section: Introductionmentioning

confidence: 99%

Low-Temperature Coherent Thermal Conduction in Thin Phononic Crystal Membranes

Puurtinen

Maasilta

2016

Crystals

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Abstract:In recent years, the idea of controlling phonon thermal transport coherently using phononic crystals has been introduced. Here, we extend our previous numerical studies of ballistic low-temperature heat transport in two-dimensional hole-array phononic crystals, and concentrate on the effect of the lattice periodicity. We find that thermal conductance can be either enhanced or reduced by large factors, depending on the the lattice period. Analysis shows that both the density of states and the average group velocity are strongly affected by the periodic structuring. The largest effect for the reduction seen for larger period structures comes from the strong reduction of the group velocities, but a contribution also comes from the reduction of the density of states. For the short period structures, the enhancement is due to the enhanced density of states.

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Thermal transport in phononic crystals and the observation of coherent phonon scattering at room temperature

Cited by 155 publications

References 36 publications

Temperature-dependent thermal conductivity in silicon nanostructured materials studied by the Boltzmann transport equation

Temperature-dependent thermal conductivity in silicon nanostructured materials studied by the Boltzmann transport equation

Low temperature heat capacity of phononic crystal membranes

Low-Temperature Coherent Thermal Conduction in Thin Phononic Crystal Membranes

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