Orbital Character Effects in the Photon Energy and Polarization Dependence of Pure C₆₀ Photoemission.

Abstract

Recent direct experimental observation of multiple highly dispersive C₆₀ valence bands has allowed for a detailed analysis of the unusual photoemission traits of these features through photon energy- and polarization-dependent measurements. Previously obscured dispersions and strong photoemission traits are now revealed by specific light polarizations. The observed intensity effects prove the locking in place of the C₆₀ molecules at low temperatures and the existence of an orientational order imposed by the substrate chosen. Most importantly, photon energy- and polarization-dependent effects are shown to be intimately linked with the orbital character of the C₆₀ band manifolds which allow for a more precise determination of the orbital character within the third highest occupied molecular orbital (HOMO-2). Our observations and analysis provide important considerations for the connection between molecular and crystalline C₆₀ electronic structure, past and future band structure studies, and for increasingly popular C₆₀ electronic device applications, especially those making use of heterostructures.