In Situ Observation of Cuprous Oxide Film Formation by Second Harmonic Generation

In situ kinetic experiments utilizing surface specific second harmonic generation are used to observe the kinetics of oxide formation from polished Cu samples treated with amidosulfonic acid under dry air and humid air. The second harmonic signal is observed to decrease upon initial exposure to dry air followed by an increase in signal after 50 minutes of exposure. This is indicative of chemisorption of O2 followed by formation of another monolayer of Cu2O. Under humid conditions, the second harmonic signal increases immediately upon exposure to air. An aqueous adlayer accelerates the rate of Cu2O formation. Finally, the kinetics of oxide formation are measured using Second Harmonic Generation on an octadecanethiol (ODT) coated Cu sample. ODT is observed to slow the growth in second harmonic signal. ODT is thus observed to slow the rate of Cu2O formation.