Surface States of Anthracene Crystals

Abstract

The existence of surface states in anthracene crystals can be deduced from the thresh-old energies for photoemission of electrons or holes from various metals into anthracene. These surface states are capable of trapping electrons as well as holes; their density is about 2 \ifmmode\times\else\texttimes\fi{} ${10}^{13}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ ${\mathrm{eV}}^{\ensuremath{-}1}$; their maximum depth is 1.3 \ifmmode\pm\else\textpm\fi{} 0.2 eV. They probably can act as recombination centers for charge carriers.