Ab initio morphology prediction of Pd, Ag, Au, and Pt nanoparticles on (0001) sapphire substrates

Abstract

We energetically predict the morphology of Pd, Ag, Au, and Pt nanoparticles on (0001) sapphire substrates, using density functional theory (DFT) simulations and the well-known Young–Dupre equation. In all cases, the contact angles exceed 90°, indicating that the nanoparticles are spherical. Notably, Au nanoparticles exhibit a higher contact angle than those of their counterparts. The validity of the proposed abinitio nanoparticle morphology prediction approach based on DFT simulations was assessed in comparison with our previous experimental findings pertaining to the time variation of the full width at half maximum (FWHM) of the resonant peak. Furthermore, the diffusivities of single Pd, Ag, Au, and Pt atoms on the substrate were evaluated by calculating the activation energy, offering insights into the underlying physics governing the timing of FWHM peaks. The analysis confirms a higher diffusivity of Au and Ag compared with Pd and Pt. According to the comparison between DFT and experiment results, although no clear relation is observed between the contact angles and timing of FWHM peaks, the diffusivity of sputtered atoms may influence the timing of FWHM peaks. Thus, timing can help to clarify the nanoparticle size, rather than shape.