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Concluding remarks and outlook. The nano-
scale structures patterned above are representative
of a versatile family of nanoelectronic devices
operating at the interface between a polar and a
nonpolar oxide insulator. The conducting nano-
structures have dimensions comparable to those
of single-walled carbon nanotubes, yet they can
be freely patterned and repeatedly modified. Their
ultimate suitability for logic and memory applica-
tions will depend on a variety of factors, such as
the mobilities of the charge carriers, how effec-
tively power dissipation can be minimized, and
whether this system can be integrated with silicon.
The devices demonstrated here suggest many
other possible applications and research directions.
With sufficient control it may be possible to
demonstrate single-electron effects such as Coulomb
blockade, resonant tunneling, or single-electron tran-
sistor behavior, possibly at room temperature. At
low temperatures, strongly correlated electron
behavior associated with low dimensionality (i.e.,
Luttinger liquid behavior) may also be accessible.
The discovery and control of superconductivity at
the LaAlO3-SrTiO3 interface (20, 21) provides a
possible avenue for exploration of mesoscopic
superconducting phenomena.
A 2-nm nanowire carrying 100 nA of current
will produce an in-plane magnetic field B ~10G
at the top surface of the LaAlO3. These magnetic
fields are large enough to excite and detect spin
waves in nearby magnetic nanostructures, and if
the frequency response can be improved, it may
be possible to sketch current loops around nano-
scale samples for nuclear magnetic resonance or
electron spin resonance experiments. On-site am-
plification of these small signals might be pos-
sible with SketchFET-based preamplifiers.
The tunnel junctions at the center of the
SketchFETs may be optimized to be sensitive to
the charge or oxidation state of the LaAlO3 sur-
face above. The active area is <5 nm2
, allowing
for high spatial selectivity for a variety of bio-
logical and chemical sensing applications.
The LaAlO3-SrTiO3 system is sufficiently ver-
satile to allow basic materials physics questions to
be addressed. Previously we showed (24) that the
measured width of written nanowires places a
strong constraint on the thickness of the q-2DEG
layer. Four-terminal resistance measurements were
performed on nanowires by creating nanowire
sense leads. The experiments with double junctions
provide new quantitative evidence for in-plane
modulation doping. Such self-referential measure-
mentswillcontinuetobeusefulinlearningmore
about this fascinating material system.