Kinetics of porous silicon growth studied using flicker-noise spectroscopy

The mechanism of the formation of porous silicon (PS) is studied using flic ker noise spectroscopy (FNS), a new phenomenological method that allows us to analyze the evolution of nonlinear dissipative systems in time, space an d energy. FNS is based on the ideas of deterministic chaos in complex macro - and microsystems. It allows us to obtain a set of empiric parameters ("pa ssport data") which characterize the state of the system and change of its properties due to the evolution in time, energy, and space. The FNS method permits us to get new information about the kinetics of growth of PS and it s properties. Thus, the PS formation mechanisms at n-Si and p-Si, as reveal ed using the FNS, seem to be essentially different. p-Si shows larger "memo ry" in the sequence of individual events involved in PS growth than n-Si (i f anodized without light illumination). The influence of the anodization va riables (such as current density, HF concentration, duration of the process , light illumination) onto the "passport data" of PS is envisaged. The incr ease of the current density increases memory of the PS formation process, w hen each forthcoming individual event is more correlated with the preceding one. Increasing current density triggers electrochemical reactions that ar e negligible at lower currents. Light illumination also produces a positive effect onto the "memory" of the system. The FNS makes it possible to disti nguish different stages of the continuous anodization process which are app arently associated with increasing pore length. Thus, FNS is a very sensiti ve tool in analysis of the PS formation and other complex electrochemical s ystems as well. (C) 2000 American Institute of Physics. [S0021-8979(00)0231 0-0].