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An investigation by AFM and TEM of the mechanism of anodic formation of nanoporosity in n-InP in KOH
O'Dwyer, Colm; Buckley, D. Noel; Sutton, David; Serantoni, M.; Newcomb, Simon B.
The early stages of nanoporous layer formation, under anodic conditions in the absence of light, were investigated for n-type InP with a carrier concentration of ∼3× 1018 cm-3 in 5 mol dm-3 KOH and a mechanism for the process is proposed. At potentials less than ∼0.35 V, spectroscopic ellipsometry and transmission electron microscopy (TEM) showed a thin oxide film on the surface. Atomic force microscopy (AFM) of electrode surfaces showed no pitting below ∼0.35 V but clearly showed etch pit formation in the range 0.4-0.53 V. The density of surface pits increased with time in both linear potential sweep and constant potential reaching a constant value at a time corresponding approximately to the current peak in linear sweep voltammograms and current-time curves at constant potential. TEM clearly showed individual nanoporous domains separated from the surface by a dense ∼40 nm InP layer. It is concluded that each domain develops as a result of directionally preferential pore propagation from an individual surface pit which forms a channel through this near-surface layer. As they grow larger, domains meet, and the merging of multiple domains eventually leads to a continuous nanoporous sub-surface region.
Keyword(s): Indium compounds; III-V semiconductors; Porous semiconductors; Nanoporous materials; Porosity; Electrochemical electrodes; Anodes; Atomic force microscopy; Transmission electron microscopy; Ellipsometry; Voltammetry (chemical analysis); Carrier density; Etching; Surface structure
Publication Date:
Type: Journal article
Peer-Reviewed: Yes
Language(s): English
Institution: University College Cork
Funder(s): Enterprise Ireland; Higher Education Authority
Citation(s): O'Dwyer, C., Buckley, D. N., Sutton, D., Serantoni, M. and Newcomb, S. B. (2007) 'An investigation by AFM and TEM of the mechanism of anodic formation of nanoporosity in n-InP in KOH', Journal of the Electrochemical Society, 154(2), pp. H78-H85.
Publisher(s): Electrochemical Society
File Format(s): application/pdf
First Indexed: 2016-07-13 05:37:23 Last Updated: 2016-10-14 06:30:10