Transformation of thin gold films morphology and tuning of surface plasmon resonance by post-growth thermal processing

The effect of vacuum heat treatment in the temperature range between 100 and 400 degrees C on the morphology and optical properties of thermally evaporated thin gold films with mass thickness from 8 to 80 nm was studied by AFM, TEM and optical spectroscopy in the spectral region of localized (surface) plasmons excitation. Our investigations have shown that change of film morphology induced by thermal annealing depends strongly on film thickness. Thus, optical behavior of thin metal films is modified due to being induced by recrystallization film permittivity changes as well as transformation of film morphology. The considered processes might be crucial for thin film optical properties determination and must be taken into account for the choice of adequate thin film optical model. Besides that, post-fabrication thermal annealing enables a wide modification of thin metal films morphology and surface plasmon resonance parameters, offering new possibilities for metal substrates design enhancing surface electromagnetic fields and therefore SERS, SEIRA, luminescence effects.