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Less than two years
ago, scientists discovered that magnesium diboride
(MgB2)--a relatively simple and readily available
metallic compound--can conduct electricity with next to no
resistance. Moreover, its superconductivity occurs at
temperatures around 39 degrees Kelvin, which is much higher
than those required for similar superconductors. But efforts
to make superconducting circuits out of the compound have so
far met with limited success.
Now Xiaoxing Xi of
Pennsylvania State University and co-workers have found a
cheap and simple method for making high-quality films of
MgB2.In the current issue of Nature Materials, Dr.
Xiaoxing Xi of Pennsylvania State University details how his
team and colleagues at the University of Michigan were able to
induce magnesium to adhere to a surface (in their case, a
template of flat sapphire crystal) with the addition of
high-pressure magnesium vapor in a vacuum chamber.
(Thin films of nobium alloys like this
could be replaced by slivers of magnesium diboride. © Applied
Superconductivity Center)
Xi's
team uses a heating coil to evaporate lumps of magnesium at
around 700 oC. The magnesium vapor then combines with
diborane, a gaseous compound of boron and hydrogen, in a
high-pressure atmosphere of hydrogen gas. Thin films of MgB2
grow on plates of a hard material such as sapphire or silicon
carbide.
Xi believes that his group's technique
will be more suitable for the
fabrication of
multilayer devices. Indeed, superconductivity expert John M.
Rowell of Northwestern University, commenting in Nature
Materials, notes that Xi' s approach to film synthesis
"promises to allow a breakthrough" in the fabrication of
multilayer devices based on MgB2.
Xiaoxing
Xi is now the Associate Professor of Physics and
Materials
Science and Engineering. He received his
Ph. D degree in Physics from Peking University in 1987. After
1989 he has been working in Rutgers University and University
of Maryland. He is the member Technical staff at
Superconducting Core Technologies, Inc. |
