Speaker
Arash Vafaei
Title
Simple, economical methods for electrical access to nanostructures used for characterizing and welding individual silver nanowire
Abstract
Elongated
nanostructures
have
attracted
a
great
deal
of
interest
due
to
unique
optical,
electrical
and
physical
properties.
In
particular,
silver
nanowires
and
nanobeams
have
proven
to
be
top
contenders
for
a
variety
of
applications.
Due
to
their
nano-sized
dimensions,
however,
electrical
access
to
individual
nanowires
is
difficult
and
expensive.
Here,
a
simple
and
economical
procedure
was
designed
to
electrically
contact
small
elongated
structures
using
common
facilities
available
at
most
universities.
A
common
lithographic
procedure
is
used
to
pattern
gold
pads
and
electrodes
on
top
of
nanowires
already
dispersed
on
a
substrate.
This
process
is
tested
by
first
characterizing,
using
a
4-point-probe
measurement,
a
novel
nanobeam
created
by
fusing
silver
nanodisks.
The
resistivity
of
the
nanobeams
was
found
to
be
as
low
as
2.7x10-8
O.m,
which
is
only
slightly
above
that
of
bulk
silver.
These
measurements
corroborate
modeling
done
by
another
group
that
the
nanodisks
align
to
create
a
nearly
continuous
crystal
rather
than
disjointed
grains.
In
the
second
application,
Joule-heating
was
used
to
actualize
a
reliable
weld
between
silver
nanowires
synthesized
using
the
polyol
method.
The
nanowires
were
situated
in
series
between
two
metal
pads,
and
a
procedure
was
designed
to
use
electrical
current
to
break
down
intermediate
layers
without
destroying
the
nanowires
themselves.
In
the
last
enterprise,
individual
silver
nanowires
were
isolated
between
two
gold
pads
and
then
using
the
same
electrical
recipe
used
for
welding
nanowires,
the
contact
resistance
was
reduced
to
a
negligible
portion
of
its
original
value.
It
was
found
that
due
to
the
reduction
in
contact
resistance,
the
2-point-probe
resistivity
of
the
nanowire
was
similar
to
those
conducted
using
4
probes.
The
invented
procedure
can
thus
allow
accurate
resistivity
measurements
of
individual
metal
nanowires
to
be
done
with
only
2
contacts
rather
than
4,
thereby
simplifying
contact
fabrication
and
allowing
appropriate
contacts
to
be
deposited
on
nanowires
as
short
as
4
µm
using
standard
photolithography.
Supervisor
Professor Irene Goldthorpe