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ductivity started
Review published the
eory explaining how, at
some materials can
y
entirely
without
on experimental clues
al hints, John Bardeen,
bert Schrieffer, all at the
in Urbana, explained
of electrical resistance
f magnetic and thermal
onductors.
Superconductivity in Germanium
Super conductivity in dimond and silicon
In 2005, the first superconducting diamond was
made by the high-pressure and high temperature
method. This discovery opened up a new field of
superconductivity in doped semiconductor . Th e
superconductivity in boron-doped diamond was
synthesized at high pressure (nearly 100,000
atmospheres) and temperature (2,500–2,800 K).
Later in 2006, E. Bustarret and C. Marcenat
succeeded to find that superconductivity can be
induced when boron is locally introduced into
silicon at concentrations above its equilibrium
solubility. For sufficiently high boron doping,
silicon becomes metallic. They fiound that at a
higher boron concentration of several per cent,
achieved by gas immersion laser doping, silicon
becomes superconducting.
Solving conductivity in an "impossible" material
Ultraclean semiconductors are by definition
unable to superconduct because at low
temperatures there are too few carriers available
to condense into the superconducting state. In
principle, one could introduce enough charge
carriers into a semiconductor, say by chemical
doping. However, the necessary doping is so high
that it often damages the semiconductor itself.
However,in2 009,
Thomas Hermannsdorfer and
collaborators from the Dresden High
Magnetic Field Laboratory and the
Forschungzentrum Dresden-Rossendorf in
Germany report superconductivity at
about 0.5K in gallium-doped germanium at
ambient pressure.
Following
diamond
and
silicon,
germanium is the third elemental
semiconductor to host superconductivity
at ambient pressure.
The challenge is to therefore reconstruct
the crystal structure by annealing, without
causing the dopants to diffuse away, float
to the surface, or cluster. The researchers
achieve that goal by using a specialized
technique called flash-lamp annealing
which employs short but intense light
pulses.
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