Effect of surface modifications on spectral shift of electroluminescence of porous n-Si in S2O82- under cathodic bias

The spectral shifts of visible electroluminescence from chemically modified porous Si under cathodic bias in an electrolyte containing S2O82- have bee n studied by luminescence and Fourier transform infrared measurements. Modi fication of porous Si with soluble polyaniline and silane compounds results in blueshifts, whereas redshifts are observed with H+ and O+ ion implantat ions. Based on a recently proposed mechanism that silicon hydride acts as a n electron injector to sulfate radical anion, the blueshift is linked to th e lowering of the energy levels of silicon hydrides on the porous Si surfac e with the bandedges being invariant with the chemical modifications. The r edshift is seen as a result of the conversion of silicon dihydride to silic on monohydride, with the energy levels of silicon monohydride lying higher than silicon dihydride. (C) 2000 The Electrochemical Society. S0013-4651(99 )04-067-7. All rights reserved.