INDUCED ZINC DESORPTION FROM ZINC-OXIDE DURING EXPOSURE TO A REDUCING AGENT

CH3CH2OD (deuterated ethanol) pulses (5 x 10(-4) ML, 20 ms) are offered to polycrystalline ZnO under ultra high vacuum conditions. The reaction products are monitored with a rate of 1000 spectra per second by a time of flight mass spectrometer, D2O and CO2, both including lattice oxygen, are observed in desorption, The creation of surface oxygen vacancies destabilizes zinc atoms nearby which appear also in desorption. The rate constant k(a) (inverse relaxation time) increases below 900 K. Above this temperature k(a) decreases. The decrease may be due to bulk oxygen diffusing to the surface and refilling the surface oxygen vacancies.