Mie scattering is an optical phenomenon that appears when electromagnetic waves, in particular light, are elastically scattered at a spherical or cylindrical object. A transfer of this phenomenon onto electron states in ballistic graphene has been proposed theoretically, assuming a well-defined incident wave scattered by a perfectly cylindrical nanometer scaled potential, but experimental fingerprints are lacking. We present an experimental demonstration of an electrical analogue to Mie scattering by using graphene as a conductor, and circular potentials arranged in a square two-dimensional array. The tabletop experiment is carried out under seemingly unfavourable conditions of diffusive transport at room-temperature. Nonetheless, when a canted arrangement of the array with respect to the incident current is chosen, cascaded Mie scattering results robustly in a transverse voltage. Its response on electrostatic gating and variation of potentials convincingly underscores Mie scattering as underlying mechanism. The findings presented here encourage the design of functional electronic metamaterials.

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A method for analysing the formation of electrical contacts to single silicon nanowires (Si NWs) by exploiting scanning electron microscopy (SEM) images, using active secondary electrons voltage contrast, is presented. Our approach clearly demonstrates the advantages of the proposed technique in analysing multiple contacts to a single nanowire simultaneously, in comparison to the conventional voltage contrast technique, where only two contact structures can be analysed, mainly for studies of the material dopant’s profile. The SEM is equipped with an in-lens detector, which collects the secondary electrons generated during electron beam exposure of the sample. Biasing the contacts with different voltages has been used to analyse the metal to Si NW contacts. The secondary electrons are sensitive to the potential distribution and the contrast of the SEM image changes depending on the number of secondary electrons detected. The Si NWs also vary their contrast together with the electrodes if they are properly electrically contacted. The basic tools and fixtures required for such measurements, and the corresponding image processing algorithms are described.