2012

An Improved Method for Differential Conductance Measurements

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As modern electronics continue to shrink, researchers are increasingly looking to nanotechnology as the basis for the next breakthrough in device size and power consumption. Indeed, as semiconductor structures are made smaller and smaller, the distinction between small silicon geometries and large molecules becomes blurred. Approached from either direction, the consequences are the same. Quantum behavior such as tunneling begins to play an important role in the electrical characteristics. In the macroscopic world, conductors may have obeyed Ohm’s Law (Figure 1a), but in the nanoscale, Ohm’s definition of resistance is no longer relevant (Figure 1b). Because the slope of the I-V curve is no longer a fundamental constant of the material, a detailed measurement of the slope of that I-V curve at every point is needed to study nanodevices. This plot of differential conductance (dG = dI/dV) is the most important measurement made on small scale devices, but presents a unique set of challenges.