A COMPARISON OF POROUS SILICON AND SILICON NANOCRYSTALLITE PHOTOLUMINESCENCE QUENCHING WITH AMINES

We report here a comparison of the ability of the monodentate Lewis ba se n-propylamine and the bidentate molecule ethylenediamine to quench the photoluminescence of light-emitting silicon in three different str uctural environments. These include porous silicon fabricated from p-t ype substrates; porous silicon from n-type substrates, and Si nanocrys tallites derived from porous silicon. Both types of porous Si substrat es were characterized by conventional transmission electron microscopy , while the Si nanocrystallites were characterized by high-resolution transmission electron microscopy. The fractional changes in photolumin escence as a consequence of amine addition were measured and fitted to a static equilibrium model from which adduct formation constants were calculated. It is found that the Si lumophores embedded in the porous oxides on n- and p-type substrates interact similarly with n-propylam ine and ethylenediamine; however, ultrasonic extraction of the nanacry stalline Si fragments from the porous oxide layers and subsequent expo sure to these amines reveals a near order of magnitude difference betw een the equilibrium constants for n?-propylamine (log K similar to 4.9 ) and ethylenediamine (log K similar to 5.8) addition.