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Spontaneous layering of porous silicon layers formed at high current densities
Author(s) -
Parkhutik Vitali,
CurielEsparza Jorge,
Millan MariCarmen,
Albella Jose
Publication year - 2005
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200461187
Subject(s) - silicon , materials science , wafer , etching (microfabrication) , dissolution , porous silicon , layer (electronics) , isotropy , anisotropy , layering , chemical physics , composite material , nanotechnology , chemistry , optoelectronics , optics , physics , botany , biology
We report here a curious effect of spontaneous fracturing of the silicon layers formed in galvanostatic conditions at medium and high current densities. Instead of formation of homogeneous p‐Si layer as at low currents, a stack of thin layers is formed. Each layer is nearly separated from others and possesses rather flat interfaces. The effects is observed using p + ‐Si wafers for the p‐Si formation and starts being noticeable at above 100 mA/cm 2 . We interpret these results in terms of the porous silicon growth model where generation of dynamic mechanical stress during the p‐Si growth causes sharp changes in Si dissolution mechanism from anisotropic etching of individual needle‐like pores in silicon to their branching and isotropic etching. At this moment p‐Si layer loses its adhesion to the surface of Si wafer and another p‐Si layer starts growing. One of the mechanisms triggering on the separation of p‐Si layers from one another is a fluctuation of local anodic current in the pore bottoms associated with gas bubble evolution during the p‐Si formation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)