One important technical hurdle that has to be overcome for using organic transistors in radio-frequency identification tags is for these devices to operate at rf frequencies (typically 13.56MHz) in the front end. It was long thought that organic transistors are too slow for this. In this letter we show that organic transistor based full-wave rectifier circuits utilizing pentacene, a p-channel organic semiconductor, can operate at this frequency with a useful efficiency. In order to achieve such high-frequency operation, we make use of the nonquasistatic state of the transistors.

Surface polarization in a poly(4-vinyl phenol) (PVP) dielectric induced by water molecules has been qualitatively investigated in pentacene thin-film transistors. The magnitudes of drain currents from devices with PVP dielectrics subject to specific surface treatments increased with humidity, whereas the opposite responses were observed from device with SiO2 dielectrics. The increase in drain current is attributed to the accumulation of extra charge carriers induced by the surface polarization in addition to that by the vertical electric field. Such polarization effects should be carefully considered in characterizing organic and polymer thin-film transistors, particularly those with polymeric gate insulators.

The isotope shifts of stable even Kr isotopes (A=78 through A=86) in the optical transitions at 432 nm and 557 nm were measured by means of polarization laser spectroscopy. The observed shifts are consistent with earlier results for other transitions. From the isotope shifts the changes in the nuclear mean square charge radii 6(r 2) were inferred using preliminary muonic isotope shift data. Starting from 78Kr0 a monotonic decrease of (r 2) with increasing mass number is found throughout the g9/2 neutron shell. The effect on 6(r 2) of nuclear deformations as well as possible contributions due to changes in the skin thickness of the nuclear charge distribution are discussed.

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Isotope shifts of the 467.8 nm line have been measured by Doppler-free saturation spectroscopy for the even Cd isotopes 106 through 116. The differential changes in mean square charge radii derived from the field shifts show a pronounced break in their trend at N=64, giving evidence for the closure of the g7/2 neutron subshell. The average charge radii determined from our data and the rms radius of l~Cd measured with muonic X-rays verify the general trend predicted by the droplet model but are off by about 35 mfm on an absolute scale. A consistent interpretation of 6 (r 2) further supports the necessity for considering changes in the skin thickness of the nuclear charge distribution.