Porosity control in metal-assisted chemical etching of degenerately doped silicon nanowires

Karthik Balasundaram, Jyothi S. Sadhu, Jae Cheol Shin, Bruno Azeredo, Debashis Chanda, Mohammad Malik, Keng Hsu, John A. Rogers, Placid Ferreira, Sanjiv Sinha, Xiuling Li

Research output: Contribution to journalArticlepeer-review

120 Scopus citations


We report the fabrication of degenerately doped silicon (Si) nanowires of different aspect ratios using a simple, low-cost and effective technique that involves metal-assisted chemical etching (MacEtch) combined with soft lithography or thermal dewetting metal patterning. We demonstrate sub-micron diameter Si nanowire arrays with aspect ratios as high as 180:1, and present the challenges in producing solid nanowires using MacEtch as the doping level increases in both p- and n-type Si. We report a systematic reduction in the porosity of these nanowires by adjusting the etching solution composition and temperature. We found that the porosity decreases from top to bottom along the axial direction and increases with etching time. With a MacEtch solution that has a high [HF]:[H 2O 2] ratio and low temperature, it is possible to form completely solid nanowires with aspect ratios of less than approximately 10:1. However, further etching to produce longer wires renders the top portion of the nanowires porous.

Original languageEnglish (US)
Article number305304
Issue number30
StatePublished - Aug 3 2012

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering
  • Electrical and Electronic Engineering


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