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Anodic formation of nanoporous indium phosphide in KOH electrolytes: effects of temperature and concentration
Quill, Nathan; Buckley, Noel; O’Dwyer, Colm; Lynch, Robert P.
Anodization of n-InP electrodes was carried out over a range of temperatures and KOH concentrations. Scanning electron microscopy showed <111>A aligned pore growth with pore width decreasing as the temperature was increased. This variation is explained in terms of the relative rates of electrochemical reaction and hole diffusion and supports the three-step model proposed earlier. As temperature is increased, both the areal density and width of surface pits decrease resulting in a large increase in the current density through the pits. This explains an observed decrease in porous layer thickness: pits sustain mass transport at the necessary rate for a shorter time before precipitation of etch products blocks the pores. As the concentration of KOH is increased, both pore width and layer thickness decrease to minima at ∼9 mol dm−3 after which they again increase. This variation of pore width is also explained by the three-step model and the variation in layer thickness is explained by mass transport effects. Layer porosity follows a similar trend to pore width, further supporting the three-step model. A transition from porous layer formation to planar etching is observed below 2 mol dm−3 KOH, and this is also explained by the three-step model.
Keyword(s): anodic; nanoporous; KOH; temperature; concentration
Publication Date:
Type: Journal article
Peer-Reviewed: Yes
Language(s): English
Institution: University of Limerick
Funder(s): Science Foundation Ireland
Citation(s): 07/SK/B1232a
Journal of The Electrochemical Society;166 (5), H3097-H3106
(37 and 70)
Publisher(s): Electrochemical Society
First Indexed: 2019-01-26 06:26:49 Last Updated: 2019-01-26 06:26:49