Surface Science LettersPlasmonic anisotropy of In nanocluster arrays on InAs(001) surface observed by differential reflectance spectroscopy

Reflectance anisotropy (RA) spectroscopy is applied to study indium nanocluster arrays formed on InAs(001) crystal surface by electrochemical treating. The measured RA spectra exhibit a resonant feature of negative sign whose scale ~ 10− 1 exceeds by two orders of magnitude the scale of the related spectra conventionally observed for semiconductor surfaces. Plasmonic origin of the resonant feature is unambiguously established both experimentally and theoretically. The RA spectra of In nanoclusters covering InAs(001) surface are interpreted in terms of coupled dipole plasmons belonging to ellipsoidal metal nanoparticles. From the experimental RA spectra, an effective plasmonic anisotropy is estimated within a lattice model of indium nanoparticle coverage. It is concluded that the in-surface semi-axes of ellipsoids can differ by a few percent, as well as the periods of rectangular lattice occupied by nanoparticles.