Surface potential (SP) of biomaterials surfaces is known to significantly influence adsorption of biological cells and biomolecules. Its modifications thus play an important role in biological and medical applications. In this work, focused electron beam typically available in scanning electron microscopes has been used to create micro-domains with modified SP on nano-crystalline hydroxyapatite thin films. The resulting SP distribution has been studied by the Kelvin probe force microscopy technique as a function of the incident electron energy in the range from 3 to 30 keV for varying beam current, i.e. speed of the charge injection. Factors limiting minimal size of such SP patterns are discusses. (C) 2012 Elsevier B. V. All rights reserved.