OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Nanoscale Electronics / Single-Electron Transport in Quantum Dot Arrays
Dene Farrell
SUNY Binghamton
Research Alliance for Minorities
www.csm.ornl.gov
Oak Ridge National Laboratory
Mentor: Jack Wells, Ph.D.
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Introduction
Nanotechnology – what is it? Science, technology and engineering dealing in
nanometer sized dimensions A nanometer is 1x10-9 meters
Nanoscale Electronics Devices of this type are different from their
macroscale counterparts Importance
Research is basic, not applied Scientists need nanoscale information processors
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Project Overview
Goal Understanding how to observe Coulomb
blockade effect in a single-electron device Procedure
Working mainly on a computational level Defining transistor properties and
analyzing behavior Results
Greater understanding of Nanoelectronics
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Island (3)
Source (1)
Drain (2)
C13 C32
R13 R32
Capacitance
Electrons Electrons
Conductance
Single-Electron Transistor
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Monte-Carlo Single-Electronics Simulator (MOSES)
FORTRAN based simulator program Utilizing Monte-Carlo method to project
transistor performance Generating Current-Voltage characteristics
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Background
Research of single electron transistors involved exposure to new concepts
Background research was major component of the internship
Key concepts:
Electron Tunneling Quantum Dots Coulomb Blockade Coulomb Staircase
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Electron Tunneling In classical mechanics, if E < V (the maximum height of the
potential barrier), the particle remains in the well forever If E > V , the particle escapes
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Electron Tunneling, Cont. In Quantum Mechanics, the electron can escape even if its energy
E is below the height of the barrier V Quantum tunneling has no counterpart in classical physics
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Quantum Dots
“Artificial Atoms” Quantum Dots Are Clusters of Atoms Behave like single atom, concerning electron
tunneling Arrays
Single-electron devices often use more than one quantum dot in one, two-dimensional patterns
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Requirements: Electron enters or departs island only via “quantum
tunneling”Well isolated conductor
High resistance tunnel junctions, (Rt >> Rk = h/e2)
Charging energy must exceed the energy of thermal fluctuations kbT
Ec e2/C >> kbT
Very small conductor as C (size)
The Coulomb Blockade and the Coulomb Staircase
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Finding The Right Conditions
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
The Coulomb Ladder
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Effects of Heat on a Nanoelectronic System
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Directed Bioassembly of Nanoelectronic Arrays
Atomic force microscope image of gold nanoparticle attached to DNA
(a) DNA-nanoparticle assembly, Functionalized gold clusters attached to DNA chain via peptide bonds.
(b) Optimized structure of the Au38(SCH3)24 cluster, obtained by quantum molecular dynamics computed on IBM supercomputer at ORNL
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Neuromorphic Signal Discrimination Two-dimensional quantum-dot array showing currents as input
channels Iin and output channels Iout
Processors for advanced sensors Requires special algorithms Success would result in the first-in-kind application
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Acknowledgments
This research was performed under the Research Alliance for Minorities Program administered through the Computer Science and Mathematics Division, Oak Ridge National Laboratory. This Program is sponsored by the Mathematical, Information, and Computational Sciences Division; Office of Advanced Scientific Computing Research; U.S. Department of Energy. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
This work has been authored by a contractor of the U.S. Government under contract DE-AC05-00OR22725. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes.
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Thank you
A special thanks to Debbie McCoy and Cheryl Hamby for being so caring and helpful and to my mentor, Jack Wells, Ph.D. you were great to work with.
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Current Modulation via External AC Potential
Novel Computational ParadigmChallenge:1nm-size islands not accessible
individuallyCannot modulate current in analogy to
Field Effect Transistors (FETs)
Idea:Control transport with external AC
potentialAdapt tunneling rate by phase locking to a
variable AC potential
Supported by experimental evidence
Wybourne, et al., Jpn. J. Appl. Phys., (1997)
Clarke, et al., APL 71 (1997)
OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY
Simulation of PAT in QD Arrays Simulations of PAT in Single-Electron Transport
Modified MOSES to include PAT transition rates Effective modulation of current by external field
Qualitative agreement with experiments by Wybourne et al
