home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Space & Astronomy
/
Space and Astronomy (October 1993).iso
/
pc
/
text
/
jplnews2
/
1296.pr
< prev
next >
Wrap
Text File
|
1993-05-03
|
4KB
|
69 lines
PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
FOR IMMEDIATE RELEASE
The first international workshop on Ballistic Electron
Emission Microscopy (BEEM) was held March 9 at NASA's Jet
Propulsion Laboratory. The workshop was hosted by JPL's Center
for Space Microelectronics Technology.
BEEM is a technique, based on scanning tunneling microscopy,
that permits probing interfaces, boundaries between different
materials, below the surfaces of semiconductors and metals.
The technique was invented at JPL in 1988 by Drs. William
Kaiser and L. Douglas Bell and is currently in use or is being
developed at dozens of laboratories around the world.
About 65 scientific representatives from the United States,
Europe and the Far East attended the workshop. The format was
informal with discussion of preliminary results and work in
progress.
Kaiser presented the keynote address reviewing the
development of BEEM at JPL. Other major research reports were
presented by Dr. Robin Williams of University of Wales at
Cardiff, Dr. Young Kuk of AT&T Bell Laboratories, Dr. Rudy Ludeke
of IBM, Dr. Hans Hallen of Cornell University, and Dr. Leo
Schowalter of Rensselaer Polytechnic Institute.
The theoretical aspects of BEEM were discussed by Dr. L.
Douglas Bell of JPL, Dr. Mark Stiles of the National Institute of
Science and Technology, and Dr. L. Craig Davis of Ford ResearchLaboratories. The workshop was chaired by Dr. Michael Hecht of
JPL.
BEEM is based on scanning tunneling microscopy, or STM,
which won its creators the Nobel Prize in Physics in 1986. It
enabled the imaging of metal and semiconductor surfaces at the
resolution of an atom.
STM uses electron tunneling across a vacuum gap between an
atom-sized probe tip and a target surface. This tunneling
process only occurs when the tip is within about one nanometer
(one billionth of a meter) of the surface. By holding the
tunneling current constant and scanning the tip across the
surface, the tip follows the surface without actually touching
it, and an image at the resolution of an atom may be obtained.
BEEM uses an STM tip to inject a highly localized electron
beam into a sample structure which has an interface below the
surface. Electrons entering the structure propagate
"ballistically," or without undergoing scattering or loss of
energy, into the material a distance of 10 nanometers or more.
Analysis of the transmitted and reflected electron currents
gives information on material quality and interface properties.
By scanning the tip across the surface, not only is a surface
image obtained as in conventional STM, but also an image of the
electron transmission across the buried interface. The resolution
of the probe is on the order of one nanometer.
BEEM, for the first time, allows detailed study of important
device interfaces and it will impact the ability to manufacture
novel electronic devices and detectors.
The workshop was presented jointly by the JPL Center for
Space Microelectronics Technology and the Southern California
American Vacuum Society, with funding provided by the Strategic
Defense Initiative Organization/Innovative Science and
Technology Office, the Office of Naval Research, the Defense
Advanced Research Projects Agency (DARPA), and the U.S. Army
Laboratory Command.
#####
#1296
3/9/90jjd