Time sequential measurement of the precursor state of oxygen on the titanium surface by means of time-of-flight spectroscopy for electron stimulated desorption

An adsorption process of oxygen on the titanium single-crystal surface of (101̄0) has been investigated by means of a time-of-flight spectrometer for the electron stimulated desorption (ESD). An oxidation experiment has been performed at the oxygen pressure ranging from 1 to 8×10 -8 Torr. TOF spectra of ESD signals were obtained sequentially by a digital acquisition system. In an initial adsorption stage, the O + ESD signal intensity grew depending on the oxygen exposure. The O + signal peaks have the most probable kinetic energies of 3.5±0.4 eV and 1.8±0.2 eV. The higher-energy peak is identified as the ESD signal from molecularly adsorbed oxygen on the surface, and the lower one as that from the chemically adsorbed oxygen.