The radio-frequency single-electron transistor (RF-SET): A fast and ultrasensitive electrometer

A new type of electrometer is described that uses a single-electron transistor (SET) and that allows large operating speeds and extremely high charge sensitivity. The SET readout was accomplished by measuring the damping of a 1.7-gigahertz resonant circuit in which the device is embedded, and in some ways is the electrostatic "dual" of the well-known radio-frequency superconducting quantum interference device. The device is more than two orders of magnitude faster than previous single-electron devices, with a constant gain from dc to greater than 100 megahertz. For a still-unoptimized device, a charge sensitivity of 1.2 x 10(-5) e/hertz was obtained at a frequency of 1.1 megahertz, which is about an order of magnitude better than a typical, 1/f-noise-limited SET, and corresponds to an energy sensitivity (in joules per hertz) of about 41 Planck's over 2pi.     

Geophysicists celebrate two satellites, mourn a third

Searching for a common theme in a gathering as diverse as the spring meeting of the American Geophysical Union (AGU) in Baltimore last month might seem futile. But satellites, both natural and artificial, provided some of the meeting's high points. Researchers reported on the first science results from the Clementine spacecraft's 2-month sojourn orbiting the moon, the revealing color of the small moon that accompanies the asteroid lda, and the planned termination of the Magellan spacecraft orbiting Venus.     

Scanned probe imaging of single-electron charge states in nanotube quantum dots

An atomic force microscope was used to study single-electron motion in nanotube quantum dots. By applying a voltage to the microscope tip, the number of electrons occupying the quantum dot could be changed, causing Coulomb oscillations in the nanotube conductance. Spatial maps of these oscillations were used to locate individual dots and to study the electrostatic coupling between the dot and the tip. The electrostatic forces associated with single electrons hopping on and off the quantum dot were also measured. These forces changed the amplitude, frequency, and quality factor of the cantilever oscillation, demonstrating how single-electron motion can interact with a mechanical oscillator.     

Thin-film transistor fabricated in single-crystalline transparent oxide semiconductor

We report the fabrication of transparent field-effect transistors using a single-crystalline thin-film transparent oxide semiconductor, InGaO3(ZnO)5, as an electron channel and amorphous hafnium oxide as a gate insulator. The device exhibits an on-to-off current ratio of approximately 106 and a field-effect mobility of approximately 80 square centimeters per volt per second at room temperature, with operation insensitive to visible light irradiation. The result provides a step toward the realization of transparent electronics for next-generation optoelectronics.     

扩展动力学平均场理论中近藤晶格模型的Luttinger Ward 泛函方法

提出了一种新的基于 Luttinger Ward 泛函的图解赝粒子方法来处理具有 RKKY 相互作用的重费米子体系的近藤晶格模型。采用此新方法,近藤晶格模型的光导结果被给出,并与已有研究结果较好相符。     

A neuron-silicon junction: a Retzius cell of the leech on an insulated-gate field-effect transistor

An identified neuron of the leech, a Retzius cell, has been attached to the open gate of a p-channel field-effect transistor. Action potentials, spontaneous or stimulated, modulate directly the source-drain current in silicon. The electronic signals match the shape of the action potential. The average voltage on the gate was up to 25 percent of the intracellular voltage change. Occasionally weak signals that resemble the first derivative of the action potential were observed. The junctions can be described by a model that includes capacitive coupling of the plasma membrane and the gate oxide and that accounts for variable resistance of the seal.     

Elastomeric transistor stamps: reversible probing of charge transport in organic crystals

We introduce a method to fabricate high-performance field-effect transistors on the surface of freestanding organic single crystals. The transistors are constructed by laminating a monolithic elastomeric transistor stamp against the surface of a crystal. This method, which eliminates exposure of the fragile organic surface to the hazards of conventional processing, enables fabrication of rubrene transistors with charge carrier mobilities as high as approximately 15 cm2/V.s and subthreshold slopes as low as 2nF.V/decade.cm2. Multiple relamination of the transistor stamp against the same crystal does not affect the transistor characteristics; we exploit this reversibility to reveal anisotropic charge transport at the basal plane of rubrene.     

Increased Surface Albedo in the Northern Hemisphere: Did satellites warn of the weather troubles of 1972 and 1973?

Routine mapping of snow and ice fields in the northern hemisphere was started by NOAA in 1967. Large year-to-year variations of the snow and pack-ice covers were observed. The annual mean coverage increased by 12 percent during 1971 and has remained high. The index R, which shows the approximate amount of energy reflected from the surface by snow and ice under the mean cloudiness, increased correspondingly. Thus, if the cloud cover over the snow fields did not increase substantially, the anomalous weather patterns of 1972 and 1973 could have been connected with the deficit in surface heat exchange which originated in the northern hemisphere the year before. During the past 7 years the largest changes occurred in the fall and in the continental interiors of Asia and America (8). Two synoptic parameters which could readily provide information on the development of snow and ice cover in the northern hemisphere are (i) the total area momentarily covered and (ii) the running annual mean of snow and ice coverage for the preceding 1-year period. By 20 September 1973 the annual mean coverage was 37.3 x 10(6) km(2), 11 to 12 percent higher than at the same time during 1968 through 1970. Snow cover-fall, the season when 15 x 10(6) to 55 x 10(6) km(2) of the northern hemisphere is covered with snow and ice, started on 20 September 1973, compared to 17 September 1972 and 5 or 10 October during 1967 through 1970. The links between the atmosphere, the oceans, and the land surfaces must be better understood before the role of snow and ice can be thoroughly explained and exploited for long-range weather forecasting. But it is clear that snow, hitherto almost overlooked in synoptic meteorological reports, must be important in the mechanism of weather changes.     

The challenge of reproducing remote sensing data from satellites and unmanned aerial vehicles (UAVs) in the context of management zones and precision agriculture

Precision Agriculture - Mapping the within-field variability of crop status is of great importance in precision agriculture, which seeks to balance agronomic inputs with spatial crop demands....