Abstract:Isotopically purified semiconductors potentially dissipate heat better than their natural, isotopically mixed counterparts as they have higher thermal conductivity (). But the benefit is low for Si at room temperature, amounting to only ~ 10% higher for bulk 28 Si than for bulk natural Si ( nat Si).We show that in stark contrast to this bulk behavior, 28 Si (99.92% enriched) nanowires have up to 150% higher than nat Si nanowires with similar diameters and surface morphology. Using firstprinciples phonon d… Show more
“…3 . The effect of isotopic enrichment on the increase of thermal conductivity has also been observed in many other materials within the temperature range of 128−380 K, such as GaN (15%) 44 , boron phosphide (17%) 45 , graphene (36%) 46 , diamond (50%) 47 , cubic boron nitride (90%) 48 , and Si NWs (150%) 49 . Fig.…”
In recent times, the unique collective transport physics of phonon hydrodynamics motivates theoreticians and experimentalists to explore it in micro- and nanoscale and at elevated temperatures. Graphitic materials have been predicted to facilitate hydrodynamic heat transport with their intrinsically strong normal scattering. However, owing to the experimental difficulties and vague theoretical understanding, the observation of phonon Poiseuille flow in graphitic systems remains challenging. In this study, based on a microscale experimental platform and the pertinent occurrence criterion in anisotropic solids, we demonstrate the existence of the phonon Poiseuille flow in a 5.5 μm-wide, suspended and isotopically purified graphite ribbon up to a temperature of 90 K. Our observation is well supported by our theoretical model based on a kinetic theory with fully first-principles inputs. Thus, this study paves the way for deeper insight into phonon hydrodynamics and cutting-edge heat manipulating applications.
“…3 . The effect of isotopic enrichment on the increase of thermal conductivity has also been observed in many other materials within the temperature range of 128−380 K, such as GaN (15%) 44 , boron phosphide (17%) 45 , graphene (36%) 46 , diamond (50%) 47 , cubic boron nitride (90%) 48 , and Si NWs (150%) 49 . Fig.…”
In recent times, the unique collective transport physics of phonon hydrodynamics motivates theoreticians and experimentalists to explore it in micro- and nanoscale and at elevated temperatures. Graphitic materials have been predicted to facilitate hydrodynamic heat transport with their intrinsically strong normal scattering. However, owing to the experimental difficulties and vague theoretical understanding, the observation of phonon Poiseuille flow in graphitic systems remains challenging. In this study, based on a microscale experimental platform and the pertinent occurrence criterion in anisotropic solids, we demonstrate the existence of the phonon Poiseuille flow in a 5.5 μm-wide, suspended and isotopically purified graphite ribbon up to a temperature of 90 K. Our observation is well supported by our theoretical model based on a kinetic theory with fully first-principles inputs. Thus, this study paves the way for deeper insight into phonon hydrodynamics and cutting-edge heat manipulating applications.
Carrier distribution and dynamics in semiconductor materials often govern their physics properties that are critical to functionalities and performance in industrial applications. The continued miniaturization of electronic and photonic devices calls for new tools to probe carrier behavior in semiconductors simultaneously at the picosecond time and nanometer length scales. Here, we develop pump-probe scattering-type scanning near-field optical microscopy (s-SNOM) to characterize the carrier dynamics in semiconductor nanowires. By coupling experiments with the point-dipole model, we resolve the size-dependent photoexcited carrier lifetime in individual silicon nanowires. We further demonstrate local carrier decay time mapping in silicon nanostructures with a sub-50 nm spatial resolution. Our pump-probe s-SNOM enables the nanoimaging of ultrafast carrier kinetics, which is an important step in advancing the future design of a broad range of electronic, photonic, and optoelectronic devices.
“…A further reduction in the κ of Si-NWs is necessary to achieve enhanced performance of thermoelectric conversion. 20,25–29…”
Section: Introductionmentioning
confidence: 99%
“…A further reduction in the k of Si-NWs is necessary to achieve enhanced performance of thermoelectric conversion. 20,[25][26][27][28][29] To enhance the thermoelectric properties, the utilization of nanostructured materials has proven to be an effective way to filter low-energy phonons or electrons by introducing interfaces or boundaries into the parent structures. [30][31][32][33][34] These interfaces, surfaces, grain boundaries (GBs), or twin boundaries (TBs) within the materials can act as barriers, thereby impeding the movement of heat carriers and inducing boundary scattering, which leads to a decrease in electronic transport properties.…”
The thermal transport properties of five-fold twinned (5FT) germanium–silicon (Ge–Si) heteronanowires (h-NWs) with varying cross-sectional areas, germanium (Ge) domain ratios and heterostructural patterns are investigated using homogeneous nonequilibrium molecular dynamics (HNEMD) simulations.
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