Height reversal in Au coverage on MoS₂ flakes/SiO₂: Thermal control of interfacial nucleation

In this study, we examined the growth of Au over monolayer MoS₂ flakes on SiO₂/Si(001) substrates at a temperature range of 25-230 °C. Based on atomic force microscopy (AFM) images, a height reversal phenomenon was observed after deposition of 2-8 nm Au. Depending on the growth temperature and Au coverage, the height difference between the MoS₂ flake and the SiO₂ area reversed from a single layer height of MoS₂ (∼+0.7 nm) to a range -1.0 to -3.5 nm. This indicates that, based on AFM data, the apparent height of Au/MoS₂ is significantly lower than that of Au/SiO₂. Scanning electron microscopy results indicate the different lateral nucleation size and shapes of Au coverage on the MoS₂ and SiO₂ surfaces. In addition, transmission electron microscopy images confirmed the two dimensional and three dimensional growth of Au on the MoS₂ and SiO₂ surfaces, respectively. The different growth modes of Au on the MoS₂ and SiO₂ surfaces led to significant changes in the apparent height and thus blocked electrical conduction. These results provide information about nucleation and morphology of Au coverage on MoS₂/SiO₂ and will be valuable for future applications.