Abstract
Exposure of luminescent n-type porous Si to gaseous molecular oxygen results in reversible quenching of the visible photoluminescence associated with this material. Steady-state and time-resolved photoluminescence quenching follow a dynamic Stern−Volmer model. From the Stern−Volmer analysis, the quenching rate constant, kq, was found to be 26 ± 9 Torr-1 s-1. The rate constant for quenching is not strongly dependent on the chemical composition of the surface. Hydride-, deuteride-, or oxide-terminated surfaces all display similar quenching rate constants. Quenching is attributed to electron transfer from the luminescent chromophore in porous Si to an O2 molecule weakly chemisorbed to a surface defect. In parallel with the reversible quenching process but on a much longer time scale (minutes to hours depending upon light intensity), porous Si samples also slowly photooxidize. Both the intensity (measured at steady state) and lifetime (measured by nanosecond-pulsed laser excitation) of photoluminescence decre...
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