9-14 Stepping and Scanning
Application — I-V curves using internal scan
SCAN for IV curves [Measure V, sweep I, constant H (magnetic field) or
T (temperature)]
SCAN can be used to measure V, while sweeping the current through a sample with a constant
magnetic field or a constant temperature. With the use of a Keithley Model 2400 SourceMeter
and a Model 8501 Trigger Link cable, (see Section 7 for more details on triggering), the 2400
can be programmed to sweep the current in a bipolar, (DC current-reversal technique) growing
amplitude fashion. See waveform in Figure 9-4. This sweep will store into the 2182 memory and
can be recalled at the end of the sweep. By having the 2400 and 2182 in a tight hardware control,
the DC current-reversal technique can be run at a rate of 8/sec. at a 1PLC integration time. This
will greatly reduce any thermal EMFs in the system by being able to reverse the DC current
before any temperature effects can occur. Looking for critical currents I
C
can be accomplished
at a faster reading rate.
NOTE Channel 1 is used to measure the voltage across the sample, while Channel 2
measures the voltage across a known reference (R
REF
) resistor to determine the
current in the sample.
Figure 9-4
Waveform to be programmed into Model 2400
P0
P1
P2
P3
P4
P5
P6
P7
P8
P9
P10
P11
...
0
+1mA
+2mA
+5mA
–1mA
–2mA
–5mA
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