We investigated heat treatment and steaming effects of silicon oxide upon the surface dissipation of contact-electrified electrons. As a result, we found that the surface diffusion of densely contact-electrified electrons on the silicon oxide surface becomes slower due to the removal of the adsorbed water layer on a silicon oxide layer by means of heat treatment, while it is enhanced by the steamed water layer. From the heat treatment and steaming effects upon the dissipation process, we concluded that the stable state of densely contact-electrified electrons becomes more stable upon removal of the water layer.
Using a standing-wave field, it is possible to trap small objects at nodes of a sound pressure distribution. In the present study, a sound wave was generated by a transducer outside of a microchannel, and propagated into a microchannel on a glass plate, where it generated a standing wave field. When water containing alumina particles was injected into the microchannel, several layers of particles were formed in the sound field. Moreover, when the ultrasound driving frequency was swept, it was possible to control the direction of the particle flow. The sound field was numerically calculated and the experimental results are discussed. #
Using reproducible and controllable contact electrification, we studied the charge dissipation of densely deposited electrons on a thin silicon oxide surface by electrostatic force measurement using a modified atomic force microscope. As a result, by increasing the density of contact-electrified electrons, we observed an appearance of a stable state of the contact-electrified electrons and its disappearance due to charge dissipation, i.e., a kind of stable-unstable phase transition. We also observed saturation of the deposited electron density with the spatial spread of deposited electrons.
Recently, we achieved reproducible and controllable contact electrification with a modified atomic force microscope (AFM). In the present paper, we report on the application of this novel microscopic method to investigate dissipation and spatial distribution of contact-electrified charges on SrTiO3 (STO) thin films with large dielectric constants. A charge dot with a Full width at half-maximum as small as 70 nm has been deposited using this technique. We also succeeded in depositing two adjacent dots with arbitrary charge signs. Thus, its potential capability for application to charge storage was clarified experimentally.
We achieved time dependent dielectric breakdown (TDDB) measurement of a thin silicon oxide microscopically using contact electrification. By increasing the external bias voltage, TDDBs of the oxide layer without and with oxide surface roughening were observed sequentially. Charge-to-breakdown in the contact electrification was estimated to be on the order of 10-5∼10-6 C/cm2. This value is higher than that of electrified charge density in the absence of external bias voltage, but is much smaller than the value of ∼5×10-1 C/cm2 obtained in the conventional TDDB measurement using a metal-oxide-semiconductor (MOS) capacitor. From calculation of the number of injected charges per atom, TDDB measurement using contact electrification is expected to provide a more quantitative evaluation of charge-to-breakdown than that using a MOS capacitor.
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