Self-assembly of beta-Ga2O3 (beta-gallium oxide) nanobelts with diameters of 50-100 nm and lengths of tens to hundreds of microns have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Under appropriate conditions such as nanobelts concentration, controlled solvent evaporation, beta-Ga2O3 nanobelts assemble into a fan-like structure on the substrate. A tendency of these nanobelts to align parallel to each other was also observed. The mechanism behind the formation of self-assembly of beta-Ga2O3 nanobelts has been proposed on the basis of lateral capillary forces. (C) 2008 Elsevier B.V. All rights reserved.