Decreasing of the thermal conductivity of Si nanopillar/SiGe composite films investigated by using a piezoelectric photothermal spectroscopy

Harada, Tomoki; Aki, Tsubasa; Ohori, Daisuke; Samukawa, Seiji; Ikari, Tetsuo; Fukuyama, Atsuhiko

doi:10.35848/1347-4065/ab82a6

Cited by 5 publications

(4 citation statements)

References 36 publications

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“…NWs have been shown to have some improved thermal properties [72]. Li et al showed Si NWs had lower thermal conductivity compared to bulk [73], which is a useful property for making more efficient power generators that use thermoelectric materials [74].…”

Section: Physical Propertiesmentioning

confidence: 99%

Defects in Self-Catalysed III-V Nanowires

Gott¹

2022

Springer Theses

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Semiconductor nanowires are poised to be a candidate for next-generation technology with superior performance and a high integration ability. They have unique physical properties that are enabled by their nano-scale form-factor. Nanowires are commonly described as being defect-free due to their ability to expel mobile defects with long-range strain fields. The droplet consumption step in self-catalysed III-V nanowires can produce material with a high density of line defects, often with null Burgers vector, i.e., no long-range strain field. The presence of such defects can diminish device performance and make them unreliable.This thesis presents an extensive study made into defects present in semiconductor nanowires. Defect structures are analysed from atomic resolution electron microscope images, and observations show that the nanowire microstructure is very different from bulk material. Nanowires can contain line defects that (a) are trapped by locks or other defects, (b) arranged as dipoles or groups with a zero total Burgers vector, or (c) have a zero Burgers vector. The most common defect is the three-monolayer high twin facet with a zero Burgers vector. Cathodoluminescence experiments reveal optical emission is quenched in defective regions, showing that they act as strong non-radiative recombination centers.Stability of defects is tested by in-situ electron microscopy to analyse defect behaviour in GaAsP nanowires using short annealing cycles. Movement of null Burgers vector defects appears to be consistent with the thermally activated singleor double-kink mechanisms of dislocation glide, with velocities that do not exceed 1 nm s −1 . Motion of null Burgers vector defects is found to depend on their size, position, and surrounding environment and sets an upper limit to activation energy around 2 eV. The majority of defects (>70%) are removed by post-growth annealing for several seconds at temperatures in excess of 640 °C, while the remaining defects do not move and are thermodynamically stable in the nanowire.Finally, axial heterostructures in GaAsP nanowires with GaAs quantum dots are examined and a selection of theoretical models are tested to see how well they fit experimental interfaces. Of the physical models tested, a model recently developed by Dubrovskii was found to best fit experimental data. Interface sharpness and size of quantum dots were measured for different nanowire radii and both showed no obvious trend. These results are explained by the low group V concentration and solubility in the catalyst, and length distribution of the nanowires respectively. xv

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Section: Physical Propertiesmentioning

confidence: 99%

Defects in Self-Catalysed III-V Nanowires

Gott¹

2022

Springer Theses

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“…3, an approach to the dynamic surface tension that involved observing the high-frequency surface tension wave was introduced. As the spatial scale of the liquid process becomes smaller, especially in recent industrial fluid processes, [53][54][55][56][57][58][59] such as inkjet technologies and microfluidics, the role of the surface properties becomes more important. The contribution of the inertia energy or energy dissipation caused by viscosity is proportional to the third power of the spatial size, while the surface energy increases linearly with the square of the size.…”

Section: Measurement Of Dynamic Properties Of Liquids By High-frequen...mentioning

confidence: 99%

Introduction to rheometry for researchers of ultrasonics

Sakai

2021

Jpn. J. Appl. Phys.

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In this paper, some recent topics on the methodology of viscoelasticity are introduced for researching ultrasonics. First, the role of viscoelasticity in ultrasonic relaxation phenomena is briefly summarized from the viewpoint of rheology. Then, the relaxation of two-dimensional viscoelasticity studied by surface light scattering experiments, which is analogous to the Brillouin scattering to detect thermal phonons, is discussed. Progress in the general method of rheometry using a rotational viscometer is also shown, in which the remote sensing of the viscosity by an electromagnetic spinning (EMS) method is described. Also examined is the possible accuracy of magneto levitated EMS, which can lead to the quantum standard of viscosity. Finally, ultrafast measurement of liquid properties, including surface tension and viscoelasticity, in which the technologies of micro liquid manipulation are employed, is introduced.

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“…[7][8][9] Research on QCM sensors has been undertaken for a long time, however, in recent years, research on useful devices focusing on piezoelectric materials other than the quartz crystal has also been actively undertaken. [10][11][12][13][14][15][16][17][18] The QCM sensor is based on a mass detection sensor that detects the mass loading caused by binding between the target substance and the sensitive film formed on the surface of the thin quartz oscillator, which vibrates in the thickness-shear resonance, as a resonance frequency change. Therefore, it is a useful sensor, which can be applied to various applications by appropriately choosing the sensitive film.…”

Section: Introductionmentioning

confidence: 99%

Study on micropillar arrangement optimization of wireless-electrodeless quartz crystal microbalance sensor and application to a gas sensor

Kato

Sato

Ato

et al. 2021

Jpn. J. Appl. Phys.

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This paper studies the structural design of the wireless-electrodeless quartz crystal microbalance (QCM) sensor, which has a rectangular AT-cut quartz oscillator installed in the microchannel fabricated by nanoimprint lithography. The quartz oscillator was supported by the micropillars in the microchannel, and by optimizing the micropillar arrangement, it was found that the structural damping could be significantly reduced by performing the finite elemental piezoelectric analysis. This behavior was then confirmed by the experiments using the evaluation chips. By supporting the four corners of the quartz oscillator with the micropillars, the structural damping could be reduced, achieving a high-quality factor (Q-factor) of about 24700. This high Q-factor was also realized in the experiments, and we investigated its application to a hydrogen-gas sensor. We succeeded in detecting hydrogen gas with an extremely low concentration of 10 ppm.

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Decreasing of the thermal conductivity of Si nanopillar/SiGe composite films investigated by using a piezoelectric photothermal spectroscopy

Cited by 5 publications

References 36 publications

Defects in Self-Catalysed III-V Nanowires

Defects in Self-Catalysed III-V Nanowires

Introduction to rheometry for researchers of ultrasonics

Study on micropillar arrangement optimization of wireless-electrodeless quartz crystal microbalance sensor and application to a gas sensor

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