Parameter dependence of pore formation in silicon within a model of local current bursts

The chemical reactions at the pr,re tip depend strongly on the choice of th e electrolyte. They define the chemical transfer rate, properties and kinet ics of the surface passivation, and ultimately the crystal orientation depe ndence of pore formation. In addition, there exists a number of processes w hich stabilize pore growth on length scales from several nm up to several 1 00 mum and determine, or at least influence, the size of pores: The potenti al distribution, carrier generation mechanisms and diffusion processes. We present a new model assuming a dissolution process which is inhomogeneous i n time and in space (i.e. a local current burst). The time scales of the cu rrent bursts and the correlation length between these current bursts define additional time and length scales for the chemical dissolution processes a t the silicon-electrolyte interface which support or even overrule the: len gth scales of the stabilizing processes listed above. This allows to design an electrolyte (using e.g, diverse organic electrolytes and oxidizing and proton supplying ingredients) to optimize macropore growth in a wide range of materials and on length scales not possible in aqueous electrolytes.