Justin Hartline - Dynamics of porous silicon formation by etching in HF + V2O5 solutions

Version 1

      Publication Details (including relevant citation   information):

      Kolasinski, Kurt W. , Hartline, Justin D. , Kelly, Bryan T.   andYadlovskiy, Julia(2010) 'Dynamics of
      porous silicon formation by etching in HF + V2O5 solutions',   Molecular Physics,, First published on: 15 April 2010 (iFirst)

      Abstract:

      Formation of porous silicon by etching of silicon wafers with   vanadium pentoxide (V2O5) dissolved
      in hydrofluoric acid (HF) has been studied with infrared   spectroscopy and electron microscopy. V2O5 creates VO2+ in   solution, which initiates the reaction by injecting holes into   the silicon valence band. Much is known about the mechanism of   etching that leads to flat Si surfaces; however, the transition   to pore formation is not well understood. The rate of film growth   depends linearly on the V2O5 concentration in aqueous solutions   but has a nonlinear dependence on the formal HF concentration.   Addition of ethanol greatly decreases the etch rate and changes   the pore morphology from a mixture of {100}+{110} planes to   predominantly {100} planes. A plot of thickness versus etch time   evolves from a quadratic to a linear dependence, whereas the   surface area depends linearly on the etch depth. These   observations are consistent with a model in which pores with a   uniform diameter nucleate randomly then lengthen linearly in   time. The pore density increases at short times and then reaches   a saturation value. The probability that the collision of a VO2+   ion with the surface leads to etching of a Si atom (reactive   sticking coefficient) is ~3*10^-8.

      Address (URL): http://dx.doi.org/10.1080/00268971003639258