The surface core level shift for lithium at the surface of lithium borate

The shallow Li 1s core level exhibits a surface-to-bulk core level shift for the stoichiometric Li2B4O7(1 1 0) surface. Angle-resolved photoemission spectroscopy was used to indentify Li 1s bulk and surface core level components at binding energies −56.5±0.4 and −53.7±0.5 eV, respectively. We find photoemission evidence for surface states of Li2B4O7(1 1 0) that exist in the gap of the projected bulk density of states. The existence of surface states is consistent with the large surface-to-bulk core level shift for the Li 1s core.