Open Access Nano Express

Ordered arrays of nanoporous silicon nanopillars and silicon nanopillars with nanoporous shells

Dong Wang1*, Ran Ji2, Song Du1, Arne Albrecht3 and Peter Schaaf1*

Author Affiliations

1 Materials for Electronics, Institute of Materials Engineering and Institute of Micro- and Nanotechnologies MacroNano®, Ilmenau University of Technology, Gustav-Kirchhoff-Str. 5, Ilmenau, 98693, Germany

2 SÜSS MicroTec Lithography GmbH, Schleissheimer Str. 90, Garching, 85748, Germany

3 Center for Micro- and Nanotechnologies MacroNano®, Ilmenau University of Technology, Gustav-Kirchhoff-Str. 7, Ilmenau, 98693, Germany

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Nanoscale Research Letters 2013, 8:42  doi:10.1186/1556-276X-8-42

Published: 21 January 2013

Abstract

The fabrication of ordered arrays of nanoporous Si nanopillars with and without nanoporous base and ordered arrays of Si nanopillars with nanoporous shells are presented. The fabrication route is using a combination of substrate conformal imprint lithography and metal-assisted chemical etching. The metal-assisted chemical etching is performed in solutions with different [HF]/[H2O2 + HF] ratios. Both pore formation and polishing (marked by the vertical etching of the nanopillars) are observed in highly doped and lightly doped Si during metal-assisted chemical etching. Pore formation is more active in the highly doped Si, while the transition from polishing to pore formation is more obvious in the lightly doped Si. The etching rate is clearly higher in the highly doped Si. Oxidation occurs on the sidewalls of the pillars by etching in solutions with small [HF]/[H2O2 + HF] ratios, leading to thinning, bending, and bonding of pillars.

Keywords:
Nanoporous Si; Pillars; Nanowires; Metal-assisted chemical etching; Nanoimprint lithography