Recently we developed a scanning force/tunneling microscope (AFM/STM), wherein the scanning tunneling microscope (STM) is combined with the atomic force microscope (AFM). This AFM/STM system enables investigation of the surface corrugation by AFM and the local conductance by STM in the same microscopic area with nanometer resolution. In the present paper, we report on the AFM/STM application to the characterization of semiconductor surfaces in air with inhomogeneous conductance and with a thin oxide film. As a result, the potential of the AFM/STM for investigating inhomogeneous conductance of ion-implanted Si(100) surfaces was clarified. Moreover the process dependence of oxidation sites on poly-Si surfaces and the voltage-dependent phenomena of thin Si oxide such as contact electrification, corona discharge and dielectric breakdown were studied.

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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. #

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.