Ph.D. Thesis - Physics

Figure 9-5: Photograph of the microfabricated trap used for ion-wire coupling experiments.
The trap is mounted in a CPGA chip carrier, and wirebond connections to the gold pads
are seen.
is shown in Fig. 9-5. The substrate is a sapphire wafer, used because of the low losses in
the GHz range sought by superconductivity researchers. For our purposes, it did not need
to be sapphire, but this works as well as other substrates for us, and the knowledge of the
Wallraff group in working with this material was available to us. The metallic layers are
as follows: 5 nm evaporated titanium (the adhesion layer), 100 nm evaporated gold, and
finally 4-5 µm electroplated gold. The final rms surface roughness, as measured using an
atomic force microscope (AFM) is 20 nm.
9.1.3 The wire
The wire used for the present experiments, and probably also for future attempts at ion-
ion coupling, is a gold wire of the type used for wirebonding, with a diameter of 25 µm.
It is mounted on a stainless steel “fork” with insulating ceramic inserted into the fork
actually making contact with the wire. The wire is glued in place on the ceramic with
UHV-compatible epoxy (EpoTek 353-ND). The fork is connected to a stack of four UHV-
(and low temperature-) compatible piezoelectric actuators, furnished by AttoCube. This
permits the control of four degrees of freedom: rotation of the fork about the piezo stack,
translation of the wire forward and backward, vertical translation, and rotation of the wire
about the axis parallel to the arms of the fork. The first and second are used to move the
wire above the trap and position it slightly to one side of the trap center. The fourth is
adjusted to make the wire as parallel as possible to the plane of the trap electrodes. It is
the third that is used in our measurements to vary the distance between the wire and ion.
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