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IR and EPR study of ammonia adsorption effect on silicon nanocrystals

IR and EPR spectroscopy is used to investigate the effect of adsorption of dry and wet ammonia on the concentration of equilibrium charge carriers in porous silicon layers with various initial types of dopants. It is found by means of IR spectroscopy that only in the presence of water molecules the ammonia adsorption results in an increase in the concentration of free charge carriers in n‐type samples up to a level exceeding 1018 cm–3. In p‐type samples, a nonmonotonic dependence of the charge‐carrier concentration on ammonia pressure is observed. By means of EPR spectroscopy in the atmosphere of wet ammonia the generation of conduction‐band electrons in p‐type silicon nanocrystals and the increase in the electron concentration in n‐type silicon nanocrystals in comparison with the initial level are observed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)