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Unformatted text preview: Demonstration of a six-dot quantum cellular automata system Islamshah Amlani, a) Alexei O. Orlov, Gregory L. Snider, Craig S. Lent, and Gary H. Bernstein Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 ~ Received 30 December 1997; accepted for publication 25 February 1998 ! We report an experimental demonstration of a logic cell for quantum-dot cellular automata ~ QCA ! . This nanostructure-based computational paradigm allows logic function implementation without the use of transistors. The four-dot QCA cell is defined by a pair of series-connected double dots, and the coupling between the input and the output double dots is provided by lithographically defined capacitors. We demonstrate that, at low temperature, an electron switch in the input double dot induces an opposite electron switch in the output double dot, resulting in a polarization change of the QCA cell. Switching is verified from the electrometer signals, which are coupled to the output double dot. We perform theoretical simulations of the device characteristics and find excellent agreement with theory. © 1998 American Institute of Physics. @ S0003-6951 ~ 98 ! 01417-X # For many years, the microelectronics industry has en- joyed unfaltering growth by scaling down the size of elec- tronic devices leading to higher speeds and denser circuit arrays. But, with the dimensions of conventional devices constantly contracting, and gate lengths shrinking toward the nanometer scale, it is becoming increasingly challenging to maintain the same pace of progress. As device feature sizes approach quantum limits, fundamental problems due to in- trinsic quantum behavior are bound to be encountered. For continual growth, a paradigm that is more atuned to the prop- erties of nanostructures holds the promise of faster speed, a lower power-delay product, and a higher level of integration. A transistorless computation paradigm, known as quantum-dot cellular automata ~ QCA ! architecture, 1–4 con- sists of nanometer-scale dots that are coupled through the Coulomb interaction. If their capacitances are sufficiently small, charge is quantized on the dots due to the Coulomb blockade of electron tunneling. 5 A basic QCA cell can be envisaged as a coupled-dot system with four dots located at the vertices of a square. Interdot tunneling may occur only in the vertical direction and interaction along the horizontal di- rection is governed by Coulombic fields. If the cell is charged with two excess electrons, they will occupy antipo- dal outer sites within the cell due to mutual electrostatic repulsion. These two polarization states of the cell can rep- resent stable states of binary logic. All Boolean logic func- tions can be realized by an appropriate arrangement of these basic cells....
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This note was uploaded on 11/28/2011 for the course COMP 790 taught by Professor Staff during the Fall '08 term at UNC.
- Fall '08