Negative resistance errors in four-point measurements of tunnel junctions and other crossed-wire devices

Negative resistance errors due to nonuniform current distributions significantly distort the apparent electronic performance of devices formed with crossed wires, demonstrated here by resistance, magnetoresistance, current-voltage, and variable temperature measurements with and without corrections. Crossed-wire devices are frequently used in research settings for exploratory systems or rapid process recipe evolution due to the ease of depositing complete devices in situ through shadow masks. Unfortunately, this geometry suffers from a negative resistance effect that dominates the measurement when the device resistance is similar to or less than the wires' resistance. We use a finite-element model and experimental data to extend work (by others) to quantify these errors when (1) devices are not square in shape, (2) when the two wires are not in the same resistivity, and (3) when the junction resistance is nonlinear in voltage. Using this knowledge and pre-existing analytical work, a straightforward method for correcting experimental measurements is suggested and evaluated. Finally, we illustrate the importance of correcting the data in magnetoresistance, current-voltage, and temperature dependent transport measurements for correct physical interpretation. [DOI: 10.1063/1.3122503]