Erosion dynamics of faceted pyramidal surfaces

Abstract

Anisotropic etching using aqueous KOH was carried out on n-type Si (100) surfaces. Atomic force microscopy (AFM) was employed to study the etched surfaces for different times. The AFM data was investigated employing dynamic scaling theory formalism. The rms roughness was found to increase with etching time except for 2 min. Roughness exponent calculations revealed that the surface became locally rougher for etching times upto 4 min after which the local roughness decreases and the system ceases to obey Family-Vicsek scaling condition. A high value (~1.882) of the growth exponent b indicates a rapid out-of-plane growth as well as faceting of the pyramids on the surface. The surface roughness evolution is found to follow an eroding system characterized by quenched random fluctuations. Finally, a vacuum annealing study done up to 1000 C reveals that atoms having lower binding energies tend to get dislodged and diffuse from about 900 C.