Red photoluminescence of gold island films

We comparatively study photoluminescence and morphology of gold films prepared with a sputtering method. The ultrathin films (less than or equal to 10 nm) efficiently emit light above 600 nm, which dramatically differs from the known emission of thick gold films. The absorption mechanism in ultrathin gold films is presumably contributed by their island structure promoting interacting plasmons. The collective plasmon states of island films decay radiatively, producing the extraordinary red emission observed under excitation at 488.0, 514.5, and 632.8 nm. The red photoluminescence of ultrathin films is substrate dependent, and correlates with the surface morphology analyzed by using atomic force microscopy and resistance measurements. (C) 2001 American Institute of Physics.