Periodic Submicron Research Articles

Unusual band effects in a 2d lattice: Superconducting properties of artificial networks and singly connected dots

Superconductivity offers an unique example in condensed matter physics where a quantum state is occupied coherently over macroscopic distances. We review some recent studies on artificial 2D superconducting microstructures including periodic and nonperiodic submicron wire networks and small superconducting dots. By measuring the phase boundary between the superconducting and normal state, the equilibrium magnetization, the magnetoresistance or the critical current, one can trace back to the spectral properties of a quantum particle on the underlying 2D lattice. Through a few examples of such superconducting model systems we illustrate some remarkable properties of Landau levels in periodic systems, as well as quantization effects in singly connected dots.

Fabrication of quasi-zero-dimensional submicron dot array and capacitance spectroscopy in a GaAs/AlGaAs heterostructure

A new and very simple technique has been developed for fabricating two-dimensional periodic submicron structures with feature size down to about 300 Å. The etching mask is made by coating the material surface with a monolayer of closely packed uniform latex particles. We have performed capacitance measurements on GaAs/AlGaAs heterostructure samples with a quasi-zero-dimensional dot array of 3300, 3640, and 3940 Å periodicities. A series of nearly equally spaced peaks in a curve of the derivative of capacitance with respect to gate voltage, which corresponds to the energy levels formed by the lateral electric confining potential, is observed.

Periodic Si-CoSi2 eutectic structures

Submicron periodicity Si-CoSi2 structures were fabricated by the directional solidification of eutectic thin films. The films, grown on oxidized Si wafers by laser recrystallization, were prepared without the ablation and cracking previously encountered. Using growth rates of up to 17 cm/s yielded lamellar periods as small as 60 nm. Defects in the lamellar structure were investigated as a function of growth rate, the shape of the solid–liquid interface, and thermal aging.

Dynamic magnetoconductivity of inversion electrons in periodic MOS-microstructures on Si

In laterally microstructured MOS-samples on Si(100) with an optically transparent periodic wire grid of submicron periodicity serving as gate, the quasistatic and dynamic conductivity of the inversion electrons are investigated at low temperatures and in high magnetic fields. At infrared frequencies we observe in addition to collective modes cyclotron resonance like modes that are shifted to higher frequencies if compared to cyclotron resonance in laterally homogeneous MOS-samples.