An AFM probe was used to locally oxide the surfaces of very smooth, 10 nm thick, epitaxial p(2+)-GaAs films grown by metalorganic molecular beam epitaxy to fabricate test structures for nanometer scale devices. Nano-oxide regions formed by AFM probe oxidation using a combination of DC and pulsed voltages were found to be extremely good insulators even under external electric fields as large as 3 MV/m. (C) 2002 Elsevier Science B.V. All rights reserved.