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Aluminum
Sample
The following schematic displays the
general setup of the Dunk Probe test. The
Aluminum sample tested during this run
(DSAT3) had a thickness of 200nm (+-) 50nm,
and dimensions of .83in by .83in. This sample
was created by sputtering onto a silicon wafer
or substrate . An electrical connection was
made with the sample by wire bonding to it
and the circuit boards attached to the test
platform, then soldering speed wire, wire
onto the corresponding sides of the circuit
board. The platform on which the test was
conducted is made out of a solid slab of
copper dimensioned to be 1.32in by 6.00in.
The sample was fixed by an apparatus
designed for this experiment. And composed
of delrin
The experiment was performed by
slowly dunking the sample, in order to
maintain thermal equilibrium and prevent
over consumption of liquid helium through
evaporation, into a bath of Liquid helium held
within a 100L Dewar.
A voltage was applied (with HP 6235A
TRIPLE OUTPUT POWER SUPPLY) to the entire
circuit, with a n 140 Ohm resistor, which had,
including the wiring and sample, a total
resistance of 141.3 Ohms measured by a fluke
meter (Fluke 87 III TRUE RMS MULTIMETER).
The voltage across the sample was measured
with the same fluke meter.
DC Voltage
Generator
Fluke
Meter
Cable
Resistance
140 Ohm Resistor
DC Voltage
Generator
DUT
Volt Meter
Cable Resistance
The following schematic portrays the
set up of the IR Dewar Test. In this run two
samples where tested, an aluminum (DSAT7)
sample 70 nm thick, dimensions of .83 by .83
inches, and deposited in Gartek; and a niobium
(ESNT4) sample 1 micron thick , dimensions of
.83 by .83, and deposited at 10 E(-7) torr and
CPA.
The samples where tested on a copper
test platform designed to fit into the IR Dewar,
and where positioned with grease. An
electrical connection was made to the samples
through wirebonds.
In the DC current run the same
equipment was used as in the Dunk Probe test.
In the AC Current run an AC current was
applied with the Agilent 33120A 15 MHz
Function / Arbitary Waveform Generator (GPIB
9). The signals from the Samples were filtered
through a Low-Noise Preamplifier Stanford
Research Systems Model SR560. The signal
from the Waveform Generator along with the
signal from the samples after passing through
the preamplifier where both measured on the
Tektronix TDS 3014 four channel color digital
phosphor oscilloscope.
Battery Powered Op Amp.
filtering C1-1k Hz); 50
0hm Resistance; 1E3
train; low noise
Signal
Generator
100 Hz
IR
Dew
ar
Pin
0ut
Oscilloscop
e 1 M Ohm
Resistance
IR Dewar AC
Oscilloscope
Wire
Resistance
DUT
Op
Amp.
Plotted Data
The following are graphs of the sample resistance versus the amount of current
going through them. The graphs are essentially flat as can be seen when one zooms
out. One can also notice that some graphs have a general trend to increase slightly
as current is increased which can be explained by an increase in temperature du to
an increase in current which would lead to an increase in resistance as phonon
scattering is increased. Some of the graphs display a general trend down and even a
sudden and sharp increase in resistance. These Are currently inexplicable and more
data is required. Overall though the points vary at .0956 Ohms for the IR Dewar Test
Ac current at 300K.
Dunk Probe Test; Resisitance of Aluminum Sample at 300K
Dunk Probe Test; Resisitance of Aluminum Sample at 300K
0.66
5
0.65
Resisitance of Sample (Ohms)
Resisitance of Sample (Ohms)
4.5
0.64
0.63
0.62
0.61
4
3.5
3
2.5
2
1.5
1
0.5
0.6
0.02
0.04
0.06
0.08
0.1
0.12
0
0.14
0
0.02
0.04
0.06
Current Through Sample (A)
0.08
0.1
0.12
0.14
0.16
0.18
Current Through Sample (A)
Dunk Probe Test; Resistance of Aluminum Sample at 4K
0.1418
Dunk Probe Test; Resistance of Aluminum Sample at 4K
0.1417
Ressistance of Sample (Ohms)
Ressistance of Sample (Ohms)
3
0.1416
0.1415
0.1414
2.5
2
1.5
1
0.5
0.1413
0
0
0.02
0.04
0.06
0.08
Current Through Sample (A)
0.02
0.04
0.06
0.08
Current Through Sample (A)
0.1
0.12
0.14
0.1
0.12
0.14
Resistance of Aluminum Sample at 4 K AC
Resistance of Aluminum Sample at 4 K AC
3
Measured Resistance (Ohms)
Measured Resistance (Ohms)
0.46
0.455
0.45
0.445
0.44
0.435
0.43
0
0.002
0.004
0.006
0.008
0.01
0.012
2.5
2
1.5
1
0.5
0
0
0.014
0.002
0.004
0.006
Current Through Sample (A)
0.008
0.01
0.012
0.014
Current Through Sample (A)
Resisitance of Aluminum Sample at 300K AC
Resisitance of Aluminum Sample at 300K AC
1.48
5
Resistance of Sample (Ohms)
Resistance of Sample (Ohms)
4.5
1.46
1.44
1.42
1.4
1.38
4
3.5
3
2.5
2
1.5
1
0.5
1.36
1
2
3
4
5
6
Curretn Through Sample (A)
7
8
9
10
x 10
-3
0
1
2
3
4
5
6
Curretn Through Sample (A)
7
8
9
10
x 10
-3
Resistance of Niobium at 300 K
3
0.36
2.5
Resistivity of Sample (Ohms)
Resistivity of Sample (Ohms)
Resistance of Niobium at 300 K
0.37
0.35
0.34
0.33
0.32
0.31
1
2
3
4
5
6
7
8
9
Current Through Sample (A)
5
x 10
2
1.5
1
0.5
0
1
10
-3
4
Resisitance of Niobium at 4K AC
-3
5
6
7
8
9
10
-3
x 10
Resisitance of Niobium at 4K AC
0.05
0.045
Resistance of Sample (Ohms)
Resistance of Sample (Ohms)
3
Current Through Sample (A)
4.5
4
3.5
3
2.5
2
1.5
1
0.5
2
x 10
0.04
0.035
0.03
0.025
0.02
0.015
0.01
0.005
0
0.05
0.1
0.15
Current Through Sample (A)
0.2
0.25
0
0
0.05
0.1
0.15
Current Through Sample (A)
0.2
0.25
Resistance of Niobium at 80.2K AC
0.1315
0.1305
0.13
0.1295
0.129
0.1285
0.128
0.1275
0.127
1
2
3
4
5
6
7
8
Current Through Sample (A)
9
-3
x 10
Resistance of Niobium at 80.2K AC
1
0.9
Resistance of Sample (Ohms)
Resistance of Sample (Ohms)
0.131
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
2
3
4
5
Current Through Sample (A)
6
7
8
9
-3
x 10
• Although precautions where taken against the
thermal electric effect by applying a AC voltage, one
can notice that the average resistance for the DC
measurement at 4K and the AC measurement at 4K
are Identical.
Average Resistance of Samples IR Dewar Test In
Ohms
•Sources of Error in the Experiment
IR Dewar Test
-In the AC Experiment the oscilloscope was used to get an
accurate reading from the Signal generator and the sample
as opposed to a fluke meter this means that the scope was
set up in parallel to the wire ring. The device functions
property under the assumption that no current is diverted
from the sample, but this of course is not an Ideal world
and thus not the case
-The oscilloscope averages the inputs It receives, when not
averaging the signal from the Sample was very fuzzy,
meaning that there was a significant amount of noise from
the sample reading; this is a source of error in the sense that
the measurements an average of noise and data , not on
absolute value
Dunk Test
-In the dunk test we were limited by the fluke meter which
can only give so much of a precise answer. Especially when
dealing with the low values at cryogenic temperatures
-We also did not account for the small changes in wire
resistance when the wires cooled which in turn would affect
our calculation of the amount of current going though the
circuit.
-The thin films where deposited on silicon, when calculating
the RRR we did not account for the silicon which is
conductive to a small extent.
Sample
Resistance
at 4K DC
Resistance
at 4K AC
Resistanc
e at 300K
AC
Aluminum
0.45143
0.45143
1.42146
6.844E-4
0.35572
Niobium
Resistance
at 80.2K
AC
0.12860
Average Resistance of Aluminum Sample
Dunk Probe Test in Ohms
Resistance Dunk
Probe at 4K DC
Resistance Dunk
Probe 300K DC
0.141386
0.636236