
Project
C2:
Friction of the Conduction of Electrons at Surfaces
We perform electromigration experiments on this self-organized silver
nanowires in-situ in a scanning electron microscope (SEM). Therefore,
the wires have to be electrically connected to our Keithley 2400 Source-Measure-Unit.
Since the wires are randomly distributed over the silicon samples
a contact structure has to be attached to each wire separately. In
a first step the position of some silver wires and silver islands
is determined and a contact layout is designed. Thereafter, a standard
electron beam lithography (EBL) process is carried out and a four
point contact structure (gold or silver contacts) is attached to the
silver wire with macroscopic bond pads. Using commercially available
chip carrier and a standard bonding technique electrical contact is
established and the electromigration experiments can be performed.

This SEM image shows a silver nanowire after the gold contact structure
is applied by means of EBL. The wire has a width of 390 nm and a length
of approximately 10 µm. One can see that the gold covers the
silver structures completely. The smaller gold stripes are the voltage
leads whereas the bigger gold pads are the current leads.

The series of SEM images above shows a silver nanowire during different
stages of an electromigration experiment. The values of the applied
current and the time during which this current was applied are given
at the right side of the image. The direction was reversed several
times during this experiment. We observe the formation of voids at
the anode of the wire. Two things are remarkable in this experiment:
First: The electromigration behaviour is
reversible when the current is reversed. Voids, which have been developed
during one part of the experiment, are closed and new voids form at
the other side of the wire.
Second: The observation of voids in electromigration
experiments usually takes place at the cathode. The atoms in the wire
move to the anode due to the so called electron wind force; vacancies
move to the opposite direction which is the cathode. In our experiment
we observe the void formation at the anode. Therefore, the wind force
cannot be the dominating driving force in our electromigration experiments
This unusual electromigration behaviour will be studied in the future
in more detail. Special interest will be paid on the role of the contact
material, since the theory predicts reversed electromigration behaviour
for small contaminations and special experimental conditions. Also
the reversibility of the mass transport has to be investigated in
more detail.


Poster:

Internationaler
Workshop 2008
C2 Hattab et al.
PDF (1.8 MB) |

Internationaler
Workshop 2008
C2 Kaspers et al.
PDF (1.6 MB) |

Internationaler
Workshop 2006
C2 Jnawali et al.
PDF (4.1 MB) |

Dresden
C2 Stahlmecke et al.
PDF (1.3 MB) |

Publications: