STRUCTURE OF SI(111) SURFACES ETCHED IN 40-PERCENT NH4F - INFLUENCE OF THE DOPING

The morphology of precisely oriented n and p(+) type Si(111) hydrogena ted surfaces has been studied by UHV-STM and AFM at ambient after ''ch emical'' etching in 40% NH4F. Whereas atomically flat surfaces are obt ained with the n-type samples, the surface of p(+) substrates is rough . It is shown that these observations stem from a variation of the par tition between the chemical (anisotropic) and the electrochemical (iso tropic) components of the etching reaction. This is the uptake of the latter reaction path at the p(+)-type specimen which explains the surf ace roughening in this case.