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Genesis and Propagation of Fractal Structures During Photoelectrochemical Etching of n-Silicon

Richter, Matthias H. and Lublow, Michael and Papadantonakis, Kimberly M. and Lewis, Nathan S. and Lewerenz, Hans-Joachim (2020) Genesis and Propagation of Fractal Structures During Photoelectrochemical Etching of n-Silicon. ACS Applied Materials & Interfaces, 12 (14). pp. 17018-17028. ISSN 1944-8244. doi:10.1021/acsami.9b22900.

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The genesis, propagation, and dimensions of fractal-etch patterns that form anodically on front- or back-illuminated n-Si(100) photoelectrodes in contact with 11.9 M NH₄F(aq) has been investigated during either linear-sweep voltammetry or when the electrode was held at a constant potential (E = +6.0 V versus Ag/AgCl). Optical images collected in situ during electrochemical experiments revealed the location and underlying mechanism of initiation and propagation of the structures on the surface. X-ray photoelectron spectroscopic (XPS) data collected for samples emersed from the electrolyte at varied times provided detailed information about the chemistry of the surface during fractal etching. The fractal structure was strongly influenced by the orientation of the crystalline Si sample. The etch patterns were initially generated at points along the circumference of bubbles that formed upon immersion of n-Si(100) samples in the electrolyte, most likely due to the electrochemical and electronic isolation of areas beneath bubbles. XPS data showed the presence of a tensile-stressed silicon surface throughout the etching process as well as the presence of SiO_xF_y on the surface. The two-dimensional fractal dimension D_(f,2D) of the patterns increased with etching time to a maximum observed value of D_(f,2D)=1.82. Promotion of fractal etching near etch masks that electrochemically and electronically isolated areas of the photoelectrode surface enabled the selective placement of highly branched structures at desired locations on an electrode surface.

Item Type:Article
Related URLs:
URLURL TypeDescription
Richter, Matthias H.0000-0003-0091-2045
Papadantonakis, Kimberly M.0000-0002-9900-5500
Lewis, Nathan S.0000-0001-5245-0538
Lewerenz, Hans-Joachim0000-0001-8433-9471
Additional Information:© 2020 American Chemical Society. Received: December 18, 2019; Accepted: March 16, 2020; Published: March 16, 2020. This work was supported through the Office of Science of the U.S. Department of Energy (DOE) under award no. DE SC0004993 to the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub. HJL is grateful for support by DFG project Le1192-4. Research was in part carried out at the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology. Dedicated to the memory of Hans-Joachim Lewerenz. The authors declare no competing financial interest.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
Deutsche Forschungsgemeinschaft (DFG)Le1192-4
Subject Keywords:Fractal structures, Silicon, Photoelectrochemistry, Photoelectron spectroscopy
Issue or Number:14
Record Number:CaltechAUTHORS:20200317-132013328
Persistent URL:
Official Citation:Genesis and Propagation of Fractal Structures During Photoelectrochemical Etching of n-Silicon. Matthias H. Richter, Michael Lublow, Kimberly M. Papadantonakis, Nathan S. Lewis, and Hans-Joachim Lewerenz. ACS Applied Materials & Interfaces 2020 12 (14), 17018-17028; DOI: 10.1021/acsami.9b22900
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101944
Deposited By: Tony Diaz
Deposited On:17 Mar 2020 20:47
Last Modified:16 Nov 2021 18:07

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