Passivation of Si surfaces by hydrogen and organic molecules investigated by in‐situ photoluminescence techniques

Abstract

AbstractWe investigated the amount of defects at Si surfaces modified by wet‐chemical etch‐back of oxide layers and varying electrochemical grafting procedures for organic molecules by means of pulsed photoluminescence (PL) techniques during the processing. The etch‐back of oxidized Si surfaces by HF containing solutions leads to a strong enhancement in PL due to hydrogenation of the surface which reduces the recombination loss of charge carriers via surface/interface states. This type of well passivated Si surface is preserved by grafting of organic molecules (exchanging the H‐Si by a C‐Si bond) which induces only small amounts of defects at the interface. The rate of grafting is reduced with decreasing pH of the aqueous solution while the PL intensity increases slightly. This behavior is a result of H‐capture from the solvent instead of binding organic molecules. Variation in the solvent for the radicalic grafting process, e.g. anhydrous acetonitrile (ACN), leads to a decrease in PL intensity since ACN itself induces surface recombination on the H‐terminated Si surface. IR spectra reveal the binding of the organic molecules due to their specific vibrational modes. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)