Imaging and spectromicroscopy of photocarrier electron dynamics in C₆₀ fullerene thin films

We have employed a two-photon photoelectron emission microscopy (2P-PEEM) to observe the photocarrier electron dynamics in an organic thin film of fullerene (C₆₀) formed on a highly oriented pyrolytic graphite with a spatial resolution of ca. 135 nm. In this approach, photocarrier electrons in C₆₀ single-layer islands generated by the first pump photon are detected by the second probe photon. These spectromicroscopic observations conducted over a 100 × 100 nm² region of C₆₀ islands consistently reproduced the macroscopic two-photon photoemission spectrum of fully covered C₆₀ monolayer film, where the energy of photocarrier electron in the islands was +0.9 eV relative to the Fermi level. Time-resolved 2P-PEEM revealed that the photocarrier electron decayed from the monolayered C₆₀ islands into the substrate with a time constant of 470 ± 30 fs.