Modification of a shallow 2DEG by AFM lithography

A conducting tip of an atomic force microscope (AFM) is used to induce ultr a-small oxide patterns on metallic (Ti) thin film and semiconducting (GaAs) surfaces. The oxide is used to deplete a shallow two-dimensional electron gas (2DEG) formed at a GaAs/AlGaAs interface, 274 Angstrom beneath the surf ace. The depleted portion of the 2DEG is rendered highly resistive and rema ins insulating over a wide voltage range at low temperatures. Furthermore, in-plane side gates, defined by oxide lines, are used to constrict the 2DEG into a narrow one-dimensional (1D) electron channel which exhibits quantiz ed conductance at low temperatures. A relatively high sub-band energy spaci ng (similar to 5.5 meV) is achieved between the first two sub-bands, demons trating the steep lateral confining potential provided by side gates throug h oxide walls. (C) 2001 Elsevier Science B.V. All rights reserved.