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Brønsted and Lewis Base Quenching of Photoemission from Luminescent ‘Porous Silicon’: Surface Protons in the Luminescence Mechanism

Published online by Cambridge University Press:  28 February 2011

J. K. M. Chun
Affiliation:
Princeton University, Frick Chemical Laboratory, Princeton, NJ 08544
A. B. Bocarsly
Affiliation:
Princeton University, Frick Chemical Laboratory, Princeton, NJ 08544
T. R. Cottrellt
Affiliation:
Princeton University, Dept. of Chemical Engineering, Princeton, NJ 08544
J. B. Benzigert
Affiliation:
Princeton University, Dept. of Chemical Engineering, Princeton, NJ 08544
J. C. Yee
Affiliation:
Princeton University, Dept. of Electrical Engineering, Princeton, NJ 08544
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Abstract

The photoluminescence (PL) observed from porous silicon (PS) is found to be very sensitive to pH. Brønsted bases quench the PL and simultaneously produce a blue shift of the p-type PS emission. Similarly, PL of n-type PS is quenched, but the emission is red shifted. Exposure to acids enhances PL and reverses the quenching due to base exposure. A pKa of 3–4 was determined for PS formed on both n- and p-type substrates, and identifies an acidic surface proton as a primary component in the PL mechanism. Variations in the intensity and energy distribution of PL as a function of temperature suggest that: 1) small changes in the hydration state of the surface may affect the emission, and 2) at least two luminescent species exist on the surface of PS; one of which is pH and temperature sensitive. SO2, a Lewis base, also quenches the PL of p-type PS quickly and reversibly. Exposure to acid is unnecessary for restoration of the PL. In contrast to reactivity with Brønsted bases, the reversibility with SO2 argues for a different quenching mechanism. Preliminary experiments show that PL is significantly quenched, ∼2–5%, by concentrations of ∼30ppm SO2 in Ar.

Type
Research Article
Copyright
Copyright © Materials Research Society 1993

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