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

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      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)


      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