We have demonstrated a surface termination effect on the photo decomposition of a monolayer (ML) pentacene film on the SrTiO3(001) single crystal surface. To prepare SrO-terminated SrTiO3(001), a SrO thin film was deposited on TiO2-terminated SrTiO3(001) by a laser molecular beam epitaxy method. The coverage of the SrO layer was precisely controlled utilizing in-situ reflection high energy electron diffraction (RHEED) intensity monitoring. The photodecomposition of the pentacene film was directly observed and quantitatively analyzed by an atomic force microscope (AFM). The 1 ML SrO was enough to completely suppress the photodecomposition of the pentacene film on SrTiO3(001). The electron transfer process from the bulk to electron scavengers such as adsorbed O-2 molecules at the surface depended greatly on the choice of the surface termination layer of SrTiO3(001), (c) 2004 Elsevier BY All rights reserved.