Porous Silicon Acoustic Devices

Koshida, Nobuyoshi

doi:10.1007/978-3-319-71381-6_132

Cited by 1 publication

(2 citation statements)

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“…The basic characteristics of these devices are consistent with the theoretical analyses of the thermo-acoustic effect and its key factors (Hu et al, 2010, 2012a,b, 2014; Vesterinen et al, 2010; Daschewski et al, 2013; Lim et al, 2013; Yang and Liu, 2013; Wang et al, 2015; Tong et al, 2017; Xing et al, 2017). Making use of the non-resonant and broad-band emissivity with no harmonic distortions, possible applications have been pursued to audible compact speaker under a full digital drive, probing source for 3-dimentional object sensing in air, acoustic pressure generator for noncontact actuation, directivity control under phased array configuration, loud speaker, noise cancellation, thermoacoustic tomography, and thermoacoustic sound projector (Koshida, 2017c; Aliev et al, 2018; Bobinger et al, 2018; Julius et al, 2018; Liu et al, 2018; Song et al, 2018).…”

Section: Emissive Properties and Applicationsmentioning

confidence: 99%

“…Due to extremely low thermal conductivity and volumetric heat capacity of the nc-Si layer (Lysenko et al, 1999; Valalaki and Nassiopoulou, 2013, 2014, 2017; Koshida, 2017b), in addition, thermo-acoustic coupling with air is enhanced. Since no mechanical vibrations are involved, this thermally induced sound emission shows non-resonant flat frequency response (Koshida, 2017c). The nc-Si sound source can effectively reproduce complicated ultrasonic communication calls between mice.…”

Section: Introductionmentioning

confidence: 99%

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Emerging Functions of Nanostructured Porous Silicon—With a Focus on the Emissive Properties of Photons, Electrons, and Ultrasound

Koshida

Nakamura

2019

Front. Chem.

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Recent topics of application studies on porous silicon (PS) are reviewed here with a focus on the emissive properties of visible light, quasiballistic hot electrons, and acoustic wave. By exposing PS in solvents to pulse laser, size-controlled nc-Si dot colloids can be formed through fragmentation of the PS layer with a considerably higher yield than the conventional techniques such as laser ablation of bulk silicon and sol-gel precursor process. Fabricated colloidal samples show strong visible photoluminescence (~40% in quantum efficiency in the red band). This provides an energy- and cost-effective route for production of nc-Si quantum dots. A multiple-tunneling transport mode through nc-Si dot chain induces efficient quasiballistic hot electron emission from an nc-Si diode. Both the efficiency and the output electron energy dispersion are remarkably improved by using monolayer graphene as a surface electrode. Being a relatively low operating voltage device compatible with silicon planar fabrication process, the emitter is applicable to mask-less parallel lithography under an active matrix drive. It has been demonstrated that the integrated 100 × 100 emitter array is useful for multibeam lithography and that the selected emission pattern is delineated with little distortion. Highly reducing activity of emitted electrons is applicable to liquid-phase thin film deposition of metals (Cu) and semiconductors (Si, Ge, and SiGe). Due to an extremely low thermal conductivity and volumetric heat capacity of nc-Si layer, on the other hand, thermo-acoustic conversion is enhanced to a practical level. A temperature fluctuation produced at the surface of nc-Si layer is quickly transferred into air, and then an acoustic wave is emitted without any mechanical vibrations. The non-resonant and broad-band emissivity with low harmonic distortions makes it possible to use the emitter for generating audible sound under a full digital drive and reproducing complicated ultrasonic communication calls between mice.

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