Electrometer

About: Electrometer is a research topic. Over the lifetime, 1210 publications have been published within this topic receiving 12431 citations.

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

Abstract: 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 × 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 ℏ.

A nanometre-scale mechanical electrometer

Abstract: The mechanical detection of charge has a long history, dating back more than 200 years to Coulomb's torsion-balance electrometer. The modern analogues of such instruments are semiconductor-based field-effect devices, the most sensitive of which are cryogenically cooled single-electron transistors. But although these latter devices have extremely high charge sensitivity, they suffer from limited bandwidth and must be operated at millikelvin temperatures in order to reduce thermal noise. Here we report the fabrication and characterization of a working nanometre-scale mechanical electrometer. We achieve a charge sensitivity of 0.1 e Hz^(-0.5), competitive with conventional semiconductor field-effect transistors; moreover, thermal noise analysis indicates that the nanometre-scale electrometer should ultimately reach sensitivities of the order of 10^(-6) e Hz^(-0.5), comparable with charge-detection capabilities of cryogenic single-electron transistors. The nanometre-scale electrometer has the additional advantages of high temperature (≥4.2 K) operation and response over a larger bandwidth, from which a diversity of applications may result.

Investigations on Lightning Discharges and on the Electric Field of Thunderstorms

Abstract: The method and apparatus used in the measurements are substantially those described in a paper "On Some Determinations of the Sign and Magnitude of Electric Discharges in Lightning Flashes." The induced charge on an exposed earthed conductor (test-plate or sphere) is used as a measure of the electric field. The testplate virtually forms part of a flat portion of the earth’s surface, and the vertical electric force or potential gradient at ground level is equal (in electrostatic measure) to 4 π Q/A, where Q is the charge on its exposed surface and A is its area. The charge Q on the earth-connected sphere of radius R, when exposed at a height h , great compared with R, is a measure of the potential at that height; the zero potential of the sphere being the resultant of the undisturbed atmospheric potential V at the height h and of the potential Q/R due to the charge on the sphere, so that Q/R = - V. The earthed conductors can be shielded from the earth’s field: the test-plate by means of an earth-connected cover, the sphere by lowering it into a conducting case resting on the ground. The quantity of electricity which flows to earth through the connecting wire on exposing or shielding the test-plate or sphere, is measured by a special type of capillary electrometer in which the readings indicate the total quantity of electricity which has traversed the instrument ; the sign and magnitude of the charge on the exposed conductor, and thus of the potential gradient, at the beginning and end of an exposure are thus determined. The sign and magnitude of sudden changes of potential gradient which occur while the conductor is exposed are indicated by the direction and magnitude of the resulting displacements of the electrometer meniscus. The total flow of electricity between the atmosphere and the test-plate or sphere during an exposure is also measured —being given by the difference between the electrometer readings before and after the exposure. The principal improvement introduced has been the provision of apparatus for giving a photographic trace of the electrometer readings; rapid changes in the field occupying less than one-tenth of a second are in this way recorded. In the observations described in the previous paper the sphere was supported in a manner which did not admit of absolute measurements being made, as the charge measured included that on the upper part of the support as well as that on the sphere itself; in these earlier measurements therefore the sphere was standardised by comparison with the test-plate. The method of supporting the sphere is now such that the charge on the sphere alone is measured, while the disturbing effect of the earthed supporting rod is small, and thus the potential at the level of the earthconnected sphere can be calculated from the charge upon it. The new method of mounting the sphere is shown in fig. 1.

Scanning Single-Electron Transistor Microscopy: Imaging Individual Charges

Abstract: A single-electron transistor scanning electrometer (SETSE)—a scanned probe microscope capable of mapping static electric fields and charges with 100-nanometer spatial resolution and a charge sensitivity of a small fraction of an electron—has been developed. The active sensing element of the SETSE, a single-electron transistor fabricated at the end of a sharp glass tip, is scanned in close proximity across the sample surface. Images of the surface electric fields of a GaAs/AlxGa1−xAs heterostructure sample show individual photo-ionized charge sites and fluctuations in the dopant and surface-charge distribution on a length scale of 100 nanometers. The SETSE has been used to image and measure depleted regions, local capacitance, band bending, and contact potentials at submicrometer length scales on the surface of this semiconductor sample.