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Title: Fabrication of ultra-high aspect ratio silicon nanopores by electrochemical etching

We report on the formation of ultra-high aspect ratio nanopores in silicon bulk material using photo-assisted electrochemical etching. Here, n-type silicon is used as anode in contact with hydrofluoric acid. Based on the local dissolution of surface atoms in pre-defined etching pits, pore growth and pore diameter are, respectively, driven and controlled by the supply of minority charge carriers generated by backside illumination. Thus, arrays with sub-100 nm wide pores were fabricated. Similar to macropore etching, it was found that the pore diameter is proportional to the etching current, i.e., smaller etching currents result in smaller pore diameters. To find the limits under which nanopores with controllable diameter still can be obtained, etching was performed at very low current densities (several μA cm{sup −2}). By local etching, straight nanopores with aspect ratios above 1000 (∼19 μm deep and ∼15 nm pore tip diameter) were achieved. However, inherent to the formation of such narrow pores is a radius of curvature of a few nanometers at the pore tip, which favors electrical breakdown resulting in rough pore wall morphologies. Lowering the applied bias is adequate to reduce spiking pores but in most cases also causes etch stop. Our findings on bulk silicon provide a realisticmore » chance towards sub-10 nm pore arrays on silicon membranes, which are of great interest for molecular filtering and possibly DNA sequencing.« less
Authors:
; ;  [1] ;  [2]
  1. Department of Materials and Nano Physics, School of Information and Communication Technology, KTH Royal Institute of Technology, Isafjordsgatan 22, SE-164 40 Kista (Sweden)
  2. Department of Fibre and Polymer Technology, Polymeric Materials and Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-100 44 Stockholm (Sweden)
Publication Date:
OSTI Identifier:
22350761
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 12; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; ANODES; ASPECT RATIO; CHARGE CARRIERS; CURRENT DENSITY; CURRENTS; DISSOLUTION; DNA SEQUENCING; ELECTRICAL FAULTS; ELECTROCHEMISTRY; ETCHING; FABRICATION; HYDROFLUORIC ACID; MEMBRANES; NANOSTRUCTURES; N-TYPE CONDUCTORS; POROUS MATERIALS; SILICON; SPECTROSCOPY; SURFACES