The electric potential of a single charge in electrolyte solution near a dielectric or a semiconducting half-space is determined in closed form when the electrostatics is described by the linear Debye-Huckel (D-H) equation. The electric potential strongly depends on the Debye length of the solution, the substrate-to-solution dielectric constant ratio, and the Debye length of the semiconductor. The technique of Hankel transforms is shown to be a useful tool in solving such axially symmetric boundary value problems for the D-H equation. (c) 2006 Elsevier Inc. All rights reserved.