Dipole model for far-field thermal emission of a nanoparticle above a planar substrate

Highlights: • generalized dipole model within framework of fluctuational electrodynamics. • thermal emission of dielectric and metallic nanoparticles in near-field of a substrate. • impact of different temperatures of nanoparticle, substrate, and environment. • theoretical basis for modelling of all scattering type near-field thermal microscopes. • divergency free derivation of electric and magnetic dressed polarizabilities. We develop a dipole model describing the thermal far-field radiation of a nanoparticle in close vicinity to a substrate. By including in our description the contribution of eddy currents and the possibility to choose different temperatures for the nanoparticle, the substrate, and the background, we generalize the existing models. We discuss the impact of the different temperatures, particle size, emission angle, and the distance dependence for all four combinations of gold and SiC nanoparticles or substrates.