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We evaluated electrical passivation of crystalline silicon wafers possessing oxidized layers using a laser terahertz (THz) emission microscope, measuring waveforms of laser-excited THz emission from those surfaces with a corona charging setup to tune surface potential without electrical contact. The THz waveform strongly correlated to the surface potential, evaluated by measuring surface photovoltage using a Kelvin probe when the surface was depleted or inverted. The waveform also correlated to the potential of the surface in the accumulation mode and inverted near the flatband condition. The minority carrier lifetime agreed with the theoretically determined dependence on the charge density. These results indicate that the surface potential of a semiconductor covered by an insulator which can be charged by the corona charging setup can be evaluated by assessing the THz emission. Further, such a sample can also be used as a reference to quantitatively relate the waveform of the THz emission and the internal field of surface band bending in semiconductors. [ABSTRACT FROM AUTHOR]

The in-plane dielectric and ferroelectric properties of c-axis oriented epitaxial strontium bismuth tantalate (SBT) thin films were investigated by interdigital surface electrode measurement. The four types of SBT thin films, which have various Sr/Bi atomic ratios, were prepared on MgO substrates by pulsed laser deposition. The dielectric properties at kilohertz and megahertz frequencies were studied from 20 to 870 K. Above room temperature, all the films show the phase transition. Sr0.99Bi1.61Ta2O9, Sr0.97Bi2.10Ta2O9, and Sr0.88Bi1.79Ta2O9 thin films show frequency dispersions near phase transition temperature. At low temperatures, dielectric and ferroelectric properties of Sr0.97Bi2.10Ta2O9 and Sr0.83Bi2.08Ta2O9 thin films were investigated. Both dielectric constant and remanent polarization show a tendency to decrease as temperature decreases, and the rapid change, which may indicate a phase transition, was observed in Sr0.97Bi2.10Ta2O9 near 80 K. [ABSTRACT FROM AUTHOR]