Quantized Conductance – A Study of Atomic Scale Conductance in Gold, Copper, Platinum, and a Platinum-Rhodium Alloy

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Hamilton, Claire
McHaffie, Scott
Ripstein, Ethan
Lam, Katrina
Morrison, Nicholas
Quantized conductance is the study of electron flow at the atomic level. One can observe quantized steps when a wire is stretched to its breaking point. At this point, the two sides of the wire are held together only by a nanometer wide chain of atoms, allowing small amounts of electrons to flow. As the wire breaks and reforms, voltage steps can be measured and displayed on an oscilloscope. The inclusion of a piezo-electric actuator allows one to observe multiple break events per second. The experiment was conducted for 4 different metals: gold, copper, platinum, and a platinum-rhodium alloy. All samples were tested in air and in a nitrogen gas saturated environment, at room temperature. The results suggested quantized conductance of copper in the nitrogen saturated environment with peaks on the conductance histograms located at 1.554 ± 3.647E-3 and 2.032 ± 3.319E-3. The peak locations indicate multiples of the quantum of conductance. Gold was found to have peaks at 0.7720 ± 1.530E-4 and 2.722 ± 2.276E-2 in a nitrogen-rich environment, and 0.7775 ± 2.344E-2 and 1.013 ± 5.274E-1 in an open system. The platinum was analyzed to have a peak at 1.045 ± 1.662E-3 in a nitrogen-rich environment, but none were observed in an open system. The platinum rhodium sample had a peak at 1.250 ± 4.241E-6 in a nitrogen saturated environment and 2.355 ± 1.563E-4 in an open system. In general, histograms produced from the gathered data yielded 0 to 2 quantization peaks but were not centered at predicted values. This discrepancy is likely due to the lack of noise mitigation in the setup.
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