A Caltech Library Service

Origin of the Electrical Barrier in Electrolessly Deposited Platinum Nanoparticles on p-Si Surfaces

Nunez, Paul and Cabán-Acevedo, Miguel and Yu, Weilai and Richter, Matthias H. and Kennedy, Kathleen and Molina Villarino, Andrés and Brunschwig, Bruce S. and Lewis, Nathan S. (2021) Origin of the Electrical Barrier in Electrolessly Deposited Platinum Nanoparticles on p-Si Surfaces. Journal of Physical Chemistry C, 125 (32). pp. 17660-17670. ISSN 1932-7447. doi:10.1021/acs.jpcc.1c03072.

[img] PDF - Supplemental Material
See Usage Policy.


Use this Persistent URL to link to this item:


Pt deposited by either sputtering or electron-beam (e-beam) evaporation on p-Si forms an ohmic contact, with zero photovoltage and very little photogenerated charge-carrier collection. However, electro- or electroless deposition of Pt onto p-Si produces a rectifying junction that generates a photovoltage of ∼300 mV under simulated 1 sun illumination. To explain these differences, we have characterized junctions formed by electroless or e-beam deposition of Pt onto H-terminated or oxide-coated p-Si substrates using impedance spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electrochemical current density vs potential (J–E) characteristics. When Pt was deposited electrolessly, XPS and TEM measurements revealed a thin interfacial SiO_x layer of 1–6 nm thickness under the Pt overlayer. Moreover, open-circuit potential measurements under illumination on electrolessly deposited Pt on a p-Si electrode showed that the junction was a function of the Nernstian potential of the contacting electrolyte solution. Creating an analogous junction by e-beam deposition of Pt required oxidation of the Si surface prior to Pt deposition, followed by etching in HF to remove oxide on the exposed Si surface. The resulting structure has both an interfacial SiO_x layer under the Pt and a H-terminated Si surface on the bare areas. Additionally, under a H₂ atmosphere, Pt can adsorb hydrogen that can diffuse to the SiO_x/Pt interface and produce a dipole layer. This information allowed formulation of a model for the charge transfer across p-Si/SiO_x/Pt interfaces. When in contact with a solution having a kinetically facile redox couple, the current is carried across the Si/electrolyte interface, and the electrode has the properties of a semiconductor/liquid junction. In contrast, when in contact with a solution with a large kinetic barrier to interfacial charge transfer, such as the hydrogen evolution reaction, the current instead passes predominantly through the SiO_x layer to the Pt and then reacts with protons in the solution. In this situation, the junction to the semiconductor is buried and occurs at the Si/SiO_x/Pt interface. The Si/SiO_x/Pt contact displays an increase in barrier height due to the hydrogen-induced dipoles. Consequently, the barrier height for an electrode made by electroless deposition of Pt onto Si is determined by the pathway that the electrons traverse to reach the solution.

Item Type:Article
Related URLs:
URLURL TypeDescription
Nunez, Paul0000-0001-7039-0516
Cabán-Acevedo, Miguel0000-0003-0054-8044
Yu, Weilai0000-0002-9420-0702
Richter, Matthias H.0000-0003-0091-2045
Kennedy, Kathleen0000-0002-7125-4871
Molina Villarino, Andrés0000-0003-3272-5156
Brunschwig, Bruce S.0000-0002-6135-6727
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2021 American Chemical Society. Received 6 April 2021. Revised 10 June 2021. Published online 6 August 2021. Published in issue 19 August 2021. 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. P.N. acknowledges support from the National Science Foundation for graduate research fellowships. Research was in part carried out at the Molecular Materials Resource Center of the Beckman Institute and at the Microanalysis Center of the California Institute of Technology. The authors thank Dr. K. Papadantonakis for assistance with editing this manuscript, and B.S.B. thanks Dr. S. Maldonado for helpful discussions. The authors declare no competing financial interest.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
NSF Graduate Research FellowshipUNSPECIFIED
Subject Keywords:Platinum, Layers, Electrodes, Deposition, X-ray photoelectron spectroscopy
Issue or Number:32
Record Number:CaltechAUTHORS:20210830-230029107
Persistent URL:
Official Citation:Origin of the Electrical Barrier in Electrolessly Deposited Platinum Nanoparticles on p-Si Surfaces Paul Nunez, Miguel Cabán-Acevedo, Weilai Yu, Matthias H. Richter, Kathleen Kennedy, Andrés Molina Villarino, Bruce S. Brunschwig, and Nathan S. Lewis The Journal of Physical Chemistry C 2021 125 (32), 17660-17670 DOI: 10.1021/acs.jpcc.1c03072
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110630
Deposited By: George Porter
Deposited On:31 Aug 2021 14:50
Last Modified:31 Aug 2021 14:50

Repository Staff Only: item control page