The thickness influence of thermal oxide layers on Si(111) substrates on the formation of self-catalyzed InAs nanowires (NWs) grown by metal-organic chemical vapor deposition (MOCVD) has been investigated It is found that the thickness of the thermal oxide layer has a strong effect on the morphological characteristics of InAs NWs formed on the Si substrates. In particular, within a suitable thickness range, it is possible to achieve vertical InAs NWs with a uniform distribution of their positions, lengths and diameters. In addition, growth on the thermal oxide layer both improves the morphology of the NWs, and suppresses the frequently observed parasitic islands compared to growth on bare Si. A growth model, which is based on the diffusion length of adatoms, the growth temperature, the thickness of thermal oxide layer, the size and the density of thermal oxide holes, has been developed to explain the formation of the self-catalyzed InAs NWs on the Si substrate with a thermal oxide layer. (C) 2014 Elsevier B.V. All rights reserved.