Very large-bandgap insulating monolayers of ODS on SiC

► Homogeneous ODS monolayers are prepared on 6H-SiC(0 0 0 1). ► HOMO-LUMO gap of about 9 eV is determined by UPS and IPE. ► Large barrier heights of about 3 eV for charge transport from substrate to adsorbate are evidence for effective electronic passivation of SiC substrate. ► Time evolution of IPE spectra elucidates origin of ODS LUMO peak.