In order to get a physical/chemical insight into the formation of nanoscale semiconductor heterojunctions, MoS2 flakes are deposited on the silicon nanowire (SiNW) array by chemical vapor deposition (CVD). In this study, H2O2 treatment provides a favorable place where the formation of Si-O bonds on the SiNW surfaces that play important roles (i.e., the nucleation centers, catalyst control centers or "seeds") can dominate the growth of MoS2 on the SiNWs. Using this configuration, the effect of a change in the S/MoO3 mass ratio (M-S/M-MoO3) on the surface morphology of MoS2 is studied. It is shown that an increase in the value of MS/MMoO3 leads to the increased nucleation rate, increasing the size of MoS2 nanopetals. This study provides valuable scientific information for directly CVD-grown edge-oriented MoS2/SiNWs heterojunctions for various nanoscale applications, including hydrogen evolution reaction and electronic and optoelectronic devices. (C) 2017 Elsevier B.V. All rights reserved.