Direct observation of confined acoustic phonon polarization branches in free-standing semiconductor nanowires

Kargar, Fariborz; Debnath, Bishwajit; Kakko, Joona-Pekko; Säynätjoki, Antti; Lipsanen, Harri; Nika, Denis L.; Lake, Roger K.; Balandin, Alexander A.

doi:10.1038/ncomms13400

Cited by 81 publications

(79 citation statements)

References 60 publications

(131 reference statements)

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“…The propensity of simple elements to aggregate into clusters is observed at diverse length scales ranging from the sub-atomic level, where combinations of three quarks form baryons 1,2 , to the super-molecular level, where large macro-molecules are composed by smaller repeated units as in DNA 3 , proteins 4 , or synthetic plastics [5][6][7] , to the scale of the Universe, where thousands of stars congregate in galaxies 8,9 . In complex systems of a great multitude of components, cooperation among components and the emergence of collective phenomena yield unique properties that are not generally expressed by components of those systems taken in isolation [10][11][12][13] . Ferromagnetism 14,15 , phonon modes of an atomic lattice 16,17 , surface enhanced Raman spectroscopy 18,19 , superconductivity 20,21 , memory and cognitive functions of the brain 22,23 , depend less on the specialization of individual elements and more on the fact that these elements interact in long-range structures. These functions are thus scale dependent and generally break down at small cluster sizes [24][25][26][27] .…”

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confidence: 99%

Cortical-like mini-columns of neuronal cells on zinc oxide nanowire surfaces

Onesto

Villani

Narducci

et al. 2019

Sci Rep

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A long-standing goal of neuroscience is a theory that explains the formation of the minicolumns in the cerebral cortex. Minicolumns are the elementary computational units of the mature neocortex. Here, we use zinc oxide nanowires with controlled topography as substrates for neural-cell growth. We observe that neuronal cells form networks where the networks characteristics exhibit a high sensitivity to the topography of the nanowires. For certain values of nanowires density and fractal dimension, neuronal networks express small world attributes, with enhanced information flows. We observe that neurons in these networks congregate in superclusters of approximately 200 neurons. We demonstrate that this number is not coincidental: the maximum number of cells in a supercluster is limited by the competition between the binding energy between cells, adhesion to the substrate, and the kinetic energy of the system. Since cortical minicolumns have similar size, similar anatomical and topological characteristics of neuronal superclusters on nanowires surfaces, we conjecture that the formation of cortical minicolumns is likewise guided by the interplay between energy minimization, information optimization and topology. For the first time, we provide a clear account of the mechanisms of formation of the minicolumns in the brain. opeNThere are amendments to this paper Scientific RepoRts | (2019) 9:4021 | https://doi.org/10.1038/s41598-019-40548-z www.nature.com/scientificreports www.nature.com/scientificreports/ architectures can direct, control and, in some cases, improve the organization of simple elements into clusters [38][39][40][41][42][43] . Nano-topography is especially important in guiding cell fate at the bio-interface, and is therefore of interest in neural tissue engineering, bio computing, biosensors operations and neural cell based sensors, the diagnosis and analysis of neurodegenerative disorders, neural development [44][45][46] . In previously reported studies 39,47,48 , we examined patterns of neuroblastoma N2A cells on meso-porous silicon. We observed that N2A cells on a surface with nano-scale motifs display an increased ability to create patterns in which the nodes of the patterns form highly clustered groups and the elements of the groups are connected by a finite, and generally low, number of steps. Networks with similar characteristics are named small world networks 49,50 . In ref. 46 we demonstrated that neural networks with a small world topology on rough silicon substrates feature enhanced signal propagation speed and computational capabilities compared to regular grids of the same size on flat surfaces.Here, we present zinc oxide nanowire surfaces with variable nanowire density that achieve a tight interface with hippocampal neurons to direct their assembly into clusters. Resulting neuronal networks show a high sensitivity to the geometrical characteristics of the nanowires. For certain combinations of fractal dimension and nanowires density, neurons accumulate into clusters with ~200 neurons per clu...

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confidence: 99%

Cortical-like mini-columns of neuronal cells on zinc oxide nanowire surfaces

Onesto

Villani

Narducci

et al. 2019

Sci Rep

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“…The phonon confinement effect has been argued in literature, some studies show that the confinement effect is only significant for low temperature, e.g., around and below 6.4 K for Si NWs with a diameter of 10.8 nm . While, other studies show that the phonon confinement occur even at room temperature …”

Section: D Nanostructures For Low Thermal Conductivitymentioning

confidence: 99%

Thermal Transport in 3D Nanostructures

Zhan

Nie

Chen

et al. 2019

Adv Funct Materials

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This work summarizes the recent progress on the thermal transport properties of 3D nanostructures, with an emphasis on experimental results. Depending on the applications, different 3D nanostructures can be prepared or designed to either achieve a low thermal conductivity for thermal insulation or thermoelectric devices or a high thermal conductivity for thermal interface materials used in the continuing miniaturization of electronics. A broad range of 3D nanostructures are discussed, ranging from colloidal crystals/assemblies, array structures, holey structures, hierarchical structures, to 3D nanostructured fillers for metal matrix composites and polymer composites. Different factors that impact the thermal conductivity of these 3D structures are compared and analyzed. This work provides an overall understanding of the thermal transport properties of various 3D nanostructures, which will shed light on the thermal management at nanoscale.

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“…Moreover, using the Brillouin light scattering, Graczykowski et al [50] studied mode propagation parallel and perpendicular to silicon strips on a silicon substrate, whereas Kargar et al [51] observed localized states in free-standing GaAs nanowires.…”

Section: Measurements Of Phononic Bandgaps and Phonon Dispersionmentioning

confidence: 99%

Phonon and heat transport control using pillar-based phononic crystals

Anufriev

Nomura

2018

Science and Technology of Advanced Materials

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Phononic crystals have been studied for the past decades as a tool to control the propagation of acoustic and mechanical waves. Recently, researchers proposed that nanosized phononic crystals can also control heat conduction and improve the thermoelectric efficiency of silicon by phonon dispersion engineering. In this review, we focus on recent theoretical and experimental advances in phonon and thermal transport engineering using pillar-based phononic crystals. First, we explain the principles of the phonon dispersion engineering and summarize early proof-of-concept experiments. Next, we review recent simulations of thermal transport in pillar-based phononic crystals and seek to uncover the origin of the observed reduction in the thermal conductivity. Finally, we discuss first experimental attempts to observe the predicted thermal conductivity reduction and suggest the directions for future research.

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Direct observation of confined acoustic phonon polarization branches in free-standing semiconductor nanowires

Cited by 81 publications

References 60 publications

Cortical-like mini-columns of neuronal cells on zinc oxide nanowire surfaces

Cortical-like mini-columns of neuronal cells on zinc oxide nanowire surfaces

Thermal Transport in 3D Nanostructures

Phonon and heat transport control using pillar-based phononic crystals

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