AVS 45th International Symposium
    Nanometer-scale Science and Technology Division Tuesday Sessions
       Session NS-TuM

Invited Paper NS-TuM1
Quantum-Dot Cellular Automata

Tuesday, November 3, 1998, 8:20 am, Room 321/322/323

Session: Quantum Structures and Molecular Electronics
Presenter: G.L. Snider, University of Notre Dame
Authors: G.L. Snider, University of Notre Dame
A.O. Orlov, University of Notre Dame
I. Amlani, University of Notre Dame
G.H. Bernstein, University of Notre Dame
C.S. Lent, University of Notre Dame
J.L. Merz, University of Notre Dame
W. Porod, University of Notre Dame
Correspondent: Click to Email
Quantum-dot Cellular Automata (QCA) is a promising architecture which employs quantum dots for digital computation. It is a revolutionary approach which addresses the issues of device density and power dissipation. It represents a concrete device design, scalable down to atomic dimensions, with possible implementations in both metals and semiconductors. A basic QCA cell consists of four quantum dots coupled capacitively and by tunnel barriers. Two excess electrons within the four dots are forced to opposite "corners" of the four-dot system by Coulomb repulsion. These two possible polarization states of the system represent logic "0" and "1". Properly arranged, arrays of these basic cells can implement the Boolean logic functions and memory needed for general purpose computation. An introduction to the QCA architecture will be presented, along experimental results from a functional QCA cell built of nanoscale metal dots defined by tunnel barriers. The QCA cell to be presented consists of two Al double-dot islands defined by tunnel junctions, capacitively coupled to each other. Al/AlO@sub x@/Al tunnel junctions are fabricated using a standard e-beam lithography/shadow evaporation technique. In addition to the QCA cell, two single-dot Al islands are capacitively coupled to the QCA cell to act as electrometers. Direct measurements of the charging diagram of QCA cell, combined with electrometer measurements of the cell, show a controlled polarization switch of the QCA cell. These and additional results confirm the control of the switching of a single electron by a single electron, and demonstrates a non-linear, bistable response in the QCA cell. There is excellent agreement between the experimental results and theory.