A surface reaction process for controlled oxide growth is disclosed using a directed, low energy ion beam for compound or oxide formation. The technique is evaluated by fabricating Ni-oxide-Ni and Cr-oxide-Ni tunneling junctions, using directed oxygen ion beams with energies ranging from about 30 to 180 eV. In one embodiment, high ion current densities are achieved at these low energies by replacing the conventional dual grid extraction system of the ion source with a single fine mesh grid. Junction resistance decreases with increasing ion energy, and oxidation time dependence shows a characteristic saturation, both consistent with a process of simultaneous oxidation and sputter etching, as in the conventional r.f. oxidation process. In contrast with r.f. oxidized junctions, however, ion beam oxidized junctions contain less contamination by backsputtering, and the quantitative nature of ion beam techniques allows greater control over the growth process.