Abstract
Tailored electrostatic potentials are at the heart of semiconductor nanostructures. We present measurements of size and screening effects of the tip-induced potential in scanning gate microscopy on a two-dimensional electron gas. First, we show methods on how to estimate the size of the tip-induced potential. Second, a ballistic cavity is studied as a function of the bias-voltage of the metallic top gates and probed with the tip-induced potential. It is shown how the potential of the cavity changes by tuning the system to a regime where conductance quantization in the constrictions formed by the tip and the top gates occurs. This conductance quantization leads to a unprecedented rich fringe pattern over the entire structure. Third, the effect of electrostatic screening of the metallic top gates is discussed.
Highlights
Scanning gate microscopy (SGM) is a powerful method to investigate local transport properties of electronic nanostructures
In the literature numbers for the size of the tip-induced potential at the Fermi energy vary between a few tens of nm and more than 1 μm depending on experimental setup and analysis procedure [1, 17,18,19,20,21,22,23,24,25,26,27,28,29,30]
In this paper we describe four different and complementary methods which allow us to determine the effective size of the tip-induced potential at the Fermi energy
Summary
Scanning gate microscopy (SGM) is a powerful method to investigate local transport properties of electronic nanostructures. In the literature numbers for the size of the tip-induced potential at the Fermi energy vary between a few tens of nm and more than 1 μm depending on experimental setup and analysis procedure [1, 17,18,19,20,21,22,23,24,25,26,27,28,29,30] Since many nanostructures, such as quantum point contacts (QPCs) and quantum dots, are formed by suitably biased top gates, the effective electronic landscape is a superposition of the gate-defined and tip-induced potential. Beyond that they are useful for SGM and in agreement with calculations
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