Unusual stabilization of Si surfaces during roughening in fluoride solution

Abstract
Surface recombination, Si–Hx bonds and initial formation of luminescing porous Si are investigated in situ by infrared and photoluminescence spectroscopy during electrochemical roughening of Si in fluoride solution. The concentration of nonradiative surface defects remains unchanged even during the formation of a rough hydrogenated Si surface. The SiH/SiH2 ratio of such a surface is constant and independent of type of doping, surface orientation, and formation of porous Si. This effect is explained by a decrease of the polarizability of Si backbonds in a disordered Si–Hx surface layer.