Investigation of the Critical Currents in Thin-Film MoGe Devices

We report on flux-flow properties of 50 nm thick thin-film amorphous MoGe bridges of different sizes with and without patterned sub-micron holes with different diameters and spacings. Characterization of the devices was carried out in liquid He at 4.2 K in a magnetic field,
H
, applied perpendicular to the device plane. Two critical currents,
I
_c1
and
I
_c2
, were studied. The current
I
_c1
is identified as the onset of a low-resistance state, whereas
I
_c2
is the current at which the device switches to a high-resistance state, and the corresponding dependences
I
_c1
(
H
) and
I
_c2
(
H
) were determined. In the absence of the holes,
I
_c1
decreases monotonically with
H
, whereas
I
_c2
(
H
) manifests lobes resembling those in the Fraunhofer-like pattern characteristic of Josephson junctions. This behavior may be due to formation of an ordered vortex lattice in some current and field ranges. Introducing the hole-line arrays modifies both
I
_c1
(
H
) and
I
_c2
(
H
) in a way that is most complicated for larger hole diameters.