Electronic states and luminescence in porous silicon quantum dots: The role of oxygen

Depending on the size, the photoluminescence (PL) of silicon quantum dots p resent in porous silicon can be tuned from the near infrared to the ultravi olet when the surface is passivated with Si-H bonds. After exposure to oxyg en, the PL shifts to the red by as much as 1 eV. This shift and the changes in PL intensity and decay time, show that both quantum confinement and sur face passivation determine the electronic states of silicon quantum dots. A theoretical model in which new electronic states appear in the band gap of the smaller quantum dots when a Si=O bond is formed, is in good agreement with experiments. This result clarifies the controversy regarding the PL me chanisms in porous silicon. [S0031-9007(98)08118-6].