An alternative method of doping and surface functionalization of diamond using a chemical route was explored. The interaction of Li with the surface and bulk of oxygen-terminated diamond was investigated using Angle-Resolved X-ray Photoemission Spectroscopy (ARXPS). A stable LiO2 termination of diamond (100) surface and doping of near-surface diamond bulk was achieved up to an annealing temperature of 850 °C. The changes in interaction between the species involved (C, O, Li) and their stoichiometric ratios at the surface were investigated as a function of annealing temperature. This was done using ARXPS peak analysis. Graphic abstract