VERY LOW-NOISE SINGLE ELECTRON TUNNELING TRANSISTORS.A team of NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. scientists, in collaboration with workers at NTT NTT Nippon Telegraph and Telephone Corporation NTT New Technology Telescope NTT National Technology Transfer, Inc NTT Name That Tune (TV game show) NTT National Tree Trust NTT Number Theoretic Transform (Nippon Telephone and Telegraph) in Japan, have confirmed extremely low noise in Si-based single-electron tunneling (SET) transistors. SET devices allow the measurement or control of the motion of single electrons; this ability has the obvious attraction for NIST that each electron has exactly the same charge, and thus SET devices hold the potential to form a fundamental standard of charge or current. At present, NIST workers are pursuing a fundamental standard of capacitance capacitance, in electricity, capability of a body, system, circuit, or device for storing electric charge. Capacitance is expressed as the ratio of stored charge in coulombs to the impressed potential difference in volts. by pumping a known number of electrons onto one plate of a capacitor capacitor or condenser, device for the storage of electric charge. Simple capacitors consist of two plates made of an electrically conducting material (e.g., a metal) and separated by a nonconducting material or dielectric (e.g. . One of the difficulties with SET devices is the well-known charge offset problem, which manifests itself as a random phase offset to the periodic dependence of current on transistor gate voltage. This makes it difficult to parallelize Par´al`lel`ize v. t. 1. To render parallel. Verb 1. parallelize - place parallel to one another lay, place, put, set, position, pose - put into a certain place or abstract location; "Put your things here"; "Set or integrate many SET devices, since one does not know a priori a priori In epistemology, knowledge that is independent of all particular experiences, as opposed to a posteriori (or empirical) knowledge, which derives from experience. whether a given gate voltage turns the device on or off. For example, in the case of the capacitance standard, this problem means that the standard must be stopped every so often to retune the gate charges. Researchers at NIST have been working for several years, without success, at overcoming the charge offset drift in metal-based SET transistors. A typical result is that such devices will significantly drift off from their original operating point within a few days. A new collaboration with workers in NTT have allowed NIST scientists to do the same measurements in Si-based devices. In the first such measurement, it was observed that, for a period of 3 weeks, the charge offset drifted by less than 0.5 %. In addition, the short-term noise is about one order of magnitude A change in quantity or volume as measured by the decimal point. For example, from tens to hundreds is one order of magnitude. Tens to thousands is two orders of magnitude; tens to millions is three orders of magnitude, etc. smaller than similar metal-based devices. This work is continuing, with the next steps being to confirm this significant improvement in a second Si-based device, and to investigate the crucial materials difference(s) causing this significant improvement in the Si-versus metal-based devices. |
|
||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion