Effect of Surface Modifications on Spectral Shift of Electroluminescence of Porous n-Si in S[sub 2]O[sub 8]2−] under Cathodic Bias

Abstract

The spectral shifts of visible electroluminescence from chemically modified porous Si under cathodic bias in an electrolyte containing S 2 O 8 2Ϫ have been studied by luminescence and Fourier transform infrared measurements. Modification of porous Si with soluble polyaniline and silane compounds results in blueshifts, whereas redshifts are observed with H ϩ and O ϩ ion implantations. Based on a recently proposed mechanism that silicon hydride acts as an electron injector to sulfate radical anion, the blueshift is linked to the lowering of the energy levels of silicon hydrides on the porous Si surface with the bandedges being invariant with the chemical modifications. The redshift is seen as a result of the conversion of silicon dihydride to silicon monohydride, with the energy levels of silicon monohydride lying higher than silicon dihydride.