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Quasi one-dimensional quantum wire arrays are fabricated by low-energy ion beam exposure of AIGaAsGaAs heterostructures containing a high-mobility two-dimensha1 electron system (ZDES). The mask used for the ion beam exposure consists of a metal grating evaporated on the crystal surface, which also serves as a gate after irradiation. This self-aligned gate allows us to change the electron density in the wires without changing the electronic wire width. The linewidths of the dimensional resonances in the far infrared (FIR) of these wire arrays confirm this assertion. The FIR transmission spectra are compared with previous results obtained using wire arrays that were density tuned with a distance-modulated gate. Furthermore, a higher-order resonance is observable, indicating that the confinement potential has non-parabolic contributions.

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Antidot superlattices on semiconductor heterostructures represent a prototype to study superlattice phenomena in systems with reduced dimensionality. The repulsive potential of an antidot replaces the positively charged ion in a threedimensional crystal leading to scattering of the carriers on the periodic lattice. The transport of electrons in antidot superlattices realized by different fabrication methods is reviewed. The focused ion beam technology can be used to create local damage to a two-dimensional electron gas in very small areas. The low magnetic field transport in this case is dominated by two length scales: the period of the lattice and the mean distance between two antidots that determines the total resistance of the system. Antidot systems with the locally repulsive potential resulting from electrostatic confinement favor the ballistic aspects of electron transport in a magnetic field. Thirdly, antidots can be created by low energy ion irradiation through a suitable photoresist grating in possible combination with homogeneous or nanostructured gate electrodes. This damage-type method allows to retain the high mobility of the electrons in the antidot lattice.

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