arXiv subjects

Satoshi Koizumi

Publications and source records attributed to Satoshi Koizumi.

5 recordsLinked to original sources

arXiv2020

Effect of deep-defect excitation on mechanical energy dissipation of single-crystal diamond

The ultra-wide bandgap of diamond distinguishes it from other semiconductors, in that all known defects have deep energy levels that are inactive at room temperature. Here, we present the effect of deep defects on the mechanical energy dissipation of single-crystal diamond experimentally and theoretically up to 973 K. Energy dissipation is found to increase with temperature and exhibits local maxima due to the interaction between phonons and deep defects activated at specific temperatures. A two-level model with deep energies is proposed to well explain the energy dissipation at elevated temperatures. It is evident that the removal of boron impurities can substantially increase the quality factor of room-temperature diamond mechanical resonators. The deep-energy nature of nitrogen bestows single-crystal diamond with outstanding low-intrinsic energy dissipation in mechanical resonators at room temperature or above.

physics.app-ph↗

arXiv2018

On-chip self-sensing enhancing actuation for MEMS/NEMS with large efficiency

The implementation of on-chip MEMS/NEMS transducers for arbitrary resonators is difficult due to a number of difficulties such as material choice, large dissipation, restriction in high frequency, low sensitivity, poor reliability, and poor integrability. We show a universal on-chip transduction scheme, which can be adapted to any MEMS/NEMS resonator. We achieve all electrical, on-chip MEMS/NEMS for any resonator.

physics.app-ph↗

arXiv2017

Interfacial energy barrier height of Al$_2$O$_3$/H-terminated (111) diamond heterointerface investigated by X-ray photoelectron spectroscopy

The interfacial band configuration of the high-k dielectric Al$_2$O$_3$ deposited at 120°C by atomic layer deposition (ALD) on boron- and phosphorus-doped hydrogen-terminated (111) diamond was investigated. Performing X-ray photoelectron spectroscopy measurements of core level binding energies and valence band maxima values, the valence band offsets of both heterojunctions are concluded to be ΔE$_V$ = 1.8 eV and ΔE$_V$ = 2.7 eV for the Al$_2$O$_3$/H(111)p and the Al$_2$O$_3$/H(111)n respectively. The ALD Al$_2$O$_3$ bandgap energy was measured from the O 1s photoelectron energy loss spectra to be $E_G^{ Al_2O_3}$ = 7.1 eV. The interfacial band diagram configuration is concluded to be of type II for both Al$_2$O$_3$/H(111)p and Al$_2$O$_3$/H(111)n heterostructures having conduction band offsets of ΔE$_C$ = 0.2 eV and ΔE$_C$ = 1.1 eV respectively. The use of doped (111) hydrogen-terminated diamond for developing future diamond MOSFET is discussed.

cond-mat.mtrl-sci↗

arXiv2017

Behavior of self-propelled acetone droplets in a Leidenfrost state on liquid substrates

It is demonstrated that non-coalescent droplets of acetone can be formed on liquid substrates. The fluid flows around and in an acetone droplet hovering on water are recorded to shed light on the mechanisms which might lead to non-coalescence. For sufficiently low impact velocities, droplets undergo a damped oscillation on the surface of the liquid substrate but at higher velocities clean bounce-off occurs. Comparisons of experimentally observed static configurations of floating droplets to predictions from a theoretical model for a small non-wetting rigid sphere resting on a liquid substrate are made and a tentative strategy for determining the thickness of the vapor layer under a small droplet on a liquid is proposed. This strategy is based on the notion of effective surface tension. The droplets show self-propulsion in straight line trajectories in a manner which can be ascribed to a Marangoni effect. Surprisingly, self-propelled droplets can become immersed beneath the undisturbed water surface. This phenomenon is reasoned to be drag-inducing and might provide a basis for refining observations in previous work.

physics.flu-dyn↗

arXiv2009

Onion structures induced by hydrophilic and hydrophobic ions in a binary mixture

Phase transition is observed between one-phase disordered phase and an ordered phase with multi-lamellar (onion) structures in an off-critical mixture of D$_2$O and 3-methylpyridine (3MP) containing a salt at 85mM. The salt consists of hydrophilic cations and hydrophobic anions, which interact asymmetrically with the solvent composition fluctuations inducing mesophases. The structure factor of the composition distribution obtained from small-angle neutron scattering has a peak at an intermediate wave number in the disordered phase and multiple peaks in the ordered phase. Lamellar layers forming onions are composed of solvation-induced charged membranes swollen by D$_2$O. The onion phase is realized only for small volume fractions of 3MP (in D$_2$O-rich solvent).

cond-mat.soft↗