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The Role of Band Bending in Affecting the Surface Recombination Velocities for Si(111) in Contact with Aqueous Acidic Electrolytes

Michalak, David J. and Gstrein, Florian and Lewis, Nathan S. (2008) The Role of Band Bending in Affecting the Surface Recombination Velocities for Si(111) in Contact with Aqueous Acidic Electrolytes. Journal of Physical Chemistry C, 112 (15). pp. 5911-5921. ISSN 1932-7447. doi:10.1021/jp075354s.

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The role of band bending in affecting surface recombination velocity measurements has been evaluated by combining barrier height data with charge-carrier lifetime measurements for Si(111) surfaces in contact with a variety of acidic aqueous electrolytes. Charge-carrier lifetimes and thus surface recombination velocities have been measured by contactless radio frequency photoconductivity decay techniques for long bulk lifetime n-Si(111) samples in contact with 11 M (40% by weight) NH_4F(aq), buffered (pH = 5) HF(aq), 27 M (48% by weight) HF(aq), or concentrated 18 M H_2SO_4. Regardless of the sample history or surface condition, long charge-carrier lifetimes were observed for n-Si(111) surfaces in contact with 11 M NH_4F(aq) or buffered HF(aq). On the basis of previous barrier height measurements, this behavior is consistent with the formation of an electrolyte-induced surface accumulation layer that reduces the rate of steady-state surface recombination even in the presence of a significant density of surface trap sites. A straightforward evaluation of the surface trap state density from the measured surface recombination velocities, S, is thus precluded for such Si/liquid contacts. In contrast, a wide range of S values, depending on the history of the sample and the state of the surface, were observed for n-Si(111) surfaces in contact with 27 M HF(aq). These results in conjunction with previously measured barrier height data indicate that the charge-carrier lifetimes measured for n-Si(111) in contact with 27 M HF(aq) can be directly correlated with the surface condition and the effective surface-state trap density. These conclusions were confirmed by measurements of the apparent S values of n-Si(111) surfaces in contact with various solutions in the presence of the known deep trap, Cu. For Si(111)/HF(aq) contacts, very high (≥920 ± 270 cm s^(-1)) surface recombination velocities were observed when 0.16 mM (10 ppm) Cu^(2+) was in the solution and/or adsorbed onto the Si(111) surface as Cu^0 deposits, whereas low (100 ± 75 or 225 ± 20 cm s^(-1)) apparent surface recombination velocities were measured for Cu-contaminated Si(111) samples in contact with 0.16 mM (10 ppm) Cu^(2+)-containing 11 M NH_4F(aq) or BHF(aq) solutions, respectively.

Item Type:Article
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Michalak, David J.0000-0002-1226-608X
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2008 American Chemical Society. Received 9 July 2007. Published online 27 March 2008. Published in print 1 April 2008. We acknowledge the NSF, Grant CHE-0604894, for support of this work. D.J.M. also acknowledges the generous support of a Link Foundation Energy Fellowship.
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Link FoundationUNSPECIFIED
Issue or Number:15
Record Number:CaltechAUTHORS:20170616-144405453
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Official Citation:The Role of Band Bending in Affecting the Surface Recombination Velocities for Si(111) in Contact with Aqueous Acidic Electrolytes David J. Michalak, Florian Gstrein, and Nathan S. Lewis The Journal of Physical Chemistry C 2008 112 (15), 5911-5921 DOI: 10.1021/jp075354s
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78298
Deposited By: Ruth Sustaita
Deposited On:16 Jun 2017 22:03
Last Modified:15 Nov 2021 17:38

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