Minority Carrier Accumulation and Interfacial Kinetics in Nanosized Pt-Dotted Silicon Electrolyte Interfaces Studied by Microwave Techniques

摘要

Photoinduced microwave conductivity (PMC) measurement allows the determination of the excess densities of accumulating minority carriers in the potential region of the kinetically limited, increasing photocurrent. Compared with PMC signals obtained with slightly oxidized naked silicon interfaces, those for the Pt-dotted silicon interfaces have a bell shaped narrow distribution and are negatively shifted with respect to the photocurrent-potential curve. It is shown that minority carrier accumulation is essentially controlled by the peculiar Si/Pt particle interfacial barrier which can be easily overcome by holes at increasingly positive potential to take advantage of the Pt-mediated reactivity. The potential and light dependent transfer rate of minority carriers at the interface strongly increases with the applied potential. Electrochemical corrosion essentially leads to a gradual modification of this barrier through formation of a Si-SiO_x-Pt structure. The influence of Fe~(2+)/Fe~(3+) concentration on the minority carrier accumulation profile as well as the photon flux dependence of the PMC signals can be explained as being due to a transport limitation phenomenon in the solution near the Pt particles.