Lublow, M. ; Lewerenz, H.J.: Phase-relations between photocurrent and in situ reflectance during photoelectrochemical dissolution of silicon. ECS Transactions 19 (2009), p. 381-389
Abstract:
The phase relation between local maxima of photocurrents and those of in-situ Brewster-angle reflectance (BAR) is investigated upon dissolution of silicon photoelectrodes in diluted NH4F. In the region of photocurrent oscillations, charge flow and optical response can be related by a linear equation which explains the observed positive phase shift of the reflectance. In the transition regime, between porous silicon formation and electropolishing, commencing surface oxidation results in a negative phase shift of the reflectance. It is shown that this observation points to a change in the dissolution mechanism of the surface-near region. A step-function, convoluted with the charge flow, is applied to model the optical behavior. This approach is compared to optical multi-layer analysis in which simultaneously increasing sub-surface porosity and surface roughness are considered.