Carrier transport mechanisms in cathodically biased meso‐porous p + ‐Si against solutions containing Fe 2+ and Co 2+ species

Autor: Bernard Gelloz, Farida Hamadache
Rok vydání: 2009
Předmět:
Zdroj: physica status solidi c. 6:1689-1693
ISSN: 1610-1642
1862-6351
Popis: This work reports on the use of the cyclic voltammetry technique to study the electrochemical behavior of porous p/sup +/-type silicon (PS) contacted by aqueous solutions containing Fe/sup 2+/ and Co/sup 2+/electro-actives species. Current-potential (I-V) measurements were performed on both flat and porous silicon substrates and different Fe/sup 2+/ concentrations were considered. With flat Si, similar I-V characteristic behaviors were obtained in 0.1 M Fe/sup 2+/ and 0. 1 M Co/sup 2+/ solutions, except that iron can be deposited from a potential more cathodic than cobalt. With porous Si, different I-V characteristic behaviors were observed and a diffusion-like current peak was detected in the presence of Fe/sup 2+/ species. The observed current peak is located near the standard redox potential of iron. However, its intensity is lower than that of Fe/sup 2+/ ions diffusion current peak and it does not increase as Fe/sup 2+/ concentration increases. A three-step carrier transport mechanism was proposed to show that the current peak could be attributed to iron nucleation on the pore walls via electroless deposition. Accordingly the difference observed in PS I-V characteristics was attributed to the fact that electroless deposition on pore walls occurs at a potential for which the reduction of Co/sup 2+/ ions is faster than that of Fe/sup 2+/ ones and it can also occur at the pore bottom via electrodeposition. These results are used to explain the poor pore filling rate with iron, reported elsewhere.
Databáze: OpenAIRE
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