PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 624 February 13, 2003   by Phillip F. Schewe, Ben Stein, James
Riordon

A PINPOINT PRECISION MAP of the cosmic microwave background, reported this
week at a press conference by scientists associated with the orbiting
Wilkinson Microwave Anisotropy Probe (WMAP), brings the early universe into
sharper focus.  The credibility of WMAP's pronouncement rests on three
things: its angular resolution is some 40 times better than that of its
microwave predecessor, the Cosmic Background Explorer (COBE); it
comprehensively surveyed the entire sky for a whole year (3 more years of
data is yet to come); and it measures the polarization of the microwave
radiation; the orientation of the radiation arises partly from the last
scattering of light at the time of  "recombination," when stable atoms
formed for the first time, and partly from the time when ultraviolet
radiation strewn by the first generation of stars ionized once again a lot
of atoms in space.  Here are a few of the salient numbers coming out of the
WMAP analysis: the time of recombination was 380,000 years after the big
bang; the era of the first stars was about 200 million years along
(surprisingly early); the age of the universe is 13.7 billion years; and the
accounting of matter in the universe is as follows: atomic matter makes up
about 4%, dark matter about 23%, and dark energy 73%.  (Websites:
http://map.gsfc.nasa.gov/;
http://www.gsfc.nasa.gov/topstory/2003/0206mapresults.html
)

SALT: THE MOVIE.  Solid, liquid, melting, and freezing are concepts that
refer to bulk matter, and not to individual atoms.  But what about a cluster
of a dozen atoms?  Louis Bloomfield (University of Virginia) has assembled a
nano-sized grain of salt, a seven-atom blob of consisting of 4 cesium atoms
and 3 iodide atoms.  Compare this to an ordinary salt grain, with a size of
.2 mm and about 1.5 million atoms along each side of its cubical structure.

By spraying this cluster with picosecond pulses of light, Bloomfield has
been able to make a "movie" of sorts showing how the cluster rearranges its
geometry: sometimes a 2x2x2 cube, sometimes a flat 2x4 ladder, sometimes an
octagonal ring, all by virtue of the cluster's own internal thermal energy;
they don't  image the cluster directly, but their locations can be inferred
from a mixture of measurement and theory (for figures and cool movie, see
http://rabi.phys.virginia.edu/research/ ).  Separate laser pulses are
used to heat or to view the clusters.  One outcome of the experiment:
"melting" of the tiny crystal begins at a "temperature"
of 225 C rather than
626 C, the melting temperature of the bulk material.  Studies like this are
pertinent to the production of nm-sized circuitry since one should know
whether a wire or some other structure will retain its basic shape or shift
into something else over time.   (Dally and Bloomfield, Physical Review
Letters, 14 February 2003 bloomfield{at}virginia.edu, 434-924-4576; see also
http://htw.wiley.com/htw/, chapter 15)

ULTRAVIOLET LITHOGRAPHY can produce lines for integrated circuits as small
as 39 nm in one recent test.  To help sustain Moore's law and cram more and
more gates and memory units into a given space, manufacturers of microchips
must make the lines in their circuitry ever smaller.  This usually means
working with a shorter-wavelength light beam for creating the patterns used
for inscribing fine features on silicon or metal surfaces.  The form of
lithography currently in mass production now can produce a half-pitch size
(equal lines and spaces in between) of 90 nm and isolated line widths of 65
nm.  To produce a later generation after that you would need even shorter
wavelengths.  At the Advanced Light Source at the Lawrence Berkeley National
Lab (LBNL) a government-industry consortium of scientists is trying out this
future lithography.  Using a beam of synchrotron radiation in the extreme
ultraviolet range they have produced 70-nm line/space intervals and isolated
lines 39 nm wide (see figure at http://www.aip.org/mgr/png/2003/179.htm ).
By the time this type of lithography comes into play, by about 2007, these
numbers should be 45 and 25 nm, respectively.  The consortium consists of a
government side, the "Virtual National Lab" (LBNL, Livermore, and Sandia),
and an industrial component comprising Intel, AMD, IBM, Infineon, Micron,
and Motorola.  (Naulleau et al., Journal of Vacuum Science Technology,
Nov/Dec 2002; contact Patrick Naulleau, pnaulleau{at}lbl.gov)


***********
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