Doping controlled roughness and defined mesoporosity in chemically etched silicon nanowires with tunable conductivity
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2013Author:
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McSweeney, W. ; Lotty, O. ; Mogili, N.V.V. ; Glynn, C. ; Geaney, H. ; Tanner, D. ; Holmes, J.D. ; O'Dwyer, C., Doping controlled roughness and defined mesoporosity in chemically etched silicon nanowires with tunable conductivity, Journal of Applied Physics, 114, 3, 2013Download Item:
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Abstract:
By using Si(100) with different dopant type (n(++)-type (As) or p-type (B)), we show how
metal-assisted chemically etched (MACE) nanowires (NWs) can form with rough outer surfaces
around a solid NW core for p-type NWs, and a unique, defined mesoporous structure for highly
doped n-type NWs. We used high resolution electron microscopy techniques to define the
characteristic roughening and mesoporous structure within the NWs and how such structures can
form due to a judicious choice of carrier concentration and dopant type. The n-type NWs have a
mesoporosity that is defined by equidistant pores in all directions, and the inter-pore distance is
correlated to the effective depletion region width at the reduction potential of the catalyst at the
silicon surface in a HF electrolyte. Clumping in n-type MACE Si NWs is also shown to be
characteristic of mesoporous NWs when etched as high density NW layers, due to low rigidity (high
porosity). Electrical transport investigations show that the etched nanowires exhibit tunable
conductance changes, where the largest resistance increase is found for highly mesoporous n-type Si
NWs, in spite of their very high electronic carrier concentration. This understanding can be adapted
to any low-dimensional semiconducting system capable of selective etching through electroless, and
possibly electrochemical, means. The process points to a method of multiscale nanostructuring
NWs, from surface roughening of NWs with controllable lengths to defined mesoporosity
formation, and may be applicable to applications where high surface area, electrical connectivity,
tunable surface structure, and internal porosity are required.
Sponsor
Grant Number
European Union
257856
Science Foundation Ireland
10/INI/13006
Irish Research Council
IRS/2011/797
Higher Education Authority
Author's Homepage:
http://people.tcd.ie/holmesjdDescription:
PUBLISHED
Author: HOLMES, JUSTIN DEREK
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Journal of Applied Physics;114;
3;
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Porous silicon, Crystalline silicon, Anodic formation, Arrays, NanostructuresLicences: