Abstract:
We address experimentally the large-scale dynamics of Si(1 0 0) surfaces during the initial
stages of anisotropic wet (KOH) chemical etching, which are characterized through atomic
force microscopy. These systems are known to lead to the formation of characteristic
pyramids, or hillocks, of typical sizes in the nanometric/micrometer scales, thus with the
potential for a large number of applications that can benefit from the nanotexturing of Si
surfaces. The present pattern formation process is very strongly disordered in space. We
assess the space correlations in such a type of rough surface and elucidate the existence of a
complex and rich morphological evolution, featuring at least three different regimes in just
10min of etching. Such a complex time behavior cannot be consistently explained within
a single formalism for dynamic scaling. The pyramidal structure reveals itself as the basic
morphological motif of the surface throughout the dynamics. A detailed analysis of the surface
slope distribution with etching time reveals that the texturing process induced by the KOH
etching is rather gradual and progressive, which accounts for the dynamic complexity. The
various stages of the morphological evolution can be accurately reproduced by computergenerated surfaces composed by uncorrelated pyramidal structures. To reach such an
agreement, the key parameters are the average pyramid size, which increases with etching
time, its distribution and the surface coverage by the pyramidal structures.
