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Published March 17, 2016 | Published
Journal Article Open

Heteroepitaxial growth of Pt and Au thin films on MgO single crystals by bias-assisted sputtering


The crystallographic orientation of a metal affects its surface energy and structure, and has profound implications for surface chemical reactions and interface engineering, which are important in areas ranging from optoelectronic device fabrication to catalysis. However, it can be very difficult and expensive to manufacture, orient, and cut single crystal metals along different crystallographic orientations, especially in the case of precious metals. One approach is to grow thin metal films epitaxially on dielectric substrates. In this work, we report on growth of Pt and Au films on MgO single crystal substrates of (100) and (110) surface orientation for use as epitaxial templates for thin film photovoltaic devices. We develop bias-assisted sputtering for deposition of oriented Pt and Au films with sub-nanometer roughness. We show that biasing the substrate decreases the substrate temperature necessary to achieve epitaxial orientation, with temperature reduction from 600 to 350 °C for Au, and from 750 to 550 °C for Pt, without use of transition metal seed layers. In addition, this temperature can be further reduced by reducing the growth rate. Biased deposition with varying substrate bias power and working pressure also enables control of the film morphology and surface roughness.

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© 2016 Macmillan Publishers Limited. This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ Received: 04 January 2016; Accepted: 02 March 2016; Published online: 17 March 2016. The authors gratefully acknowledge support from the Dow Chemical Company under the earth-abundant semiconductor project, and by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award No. DE-SC0004993. This material is based upon work supported in part by the National Science Foundation (NSF) and the Department of Energy (DOE) under NSF CA No. EEC-1041895. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect those of NSF or DOE. Author Contributions: Y.T. designed and performed experiments and data analysis, and drafted the manuscript. S.T.O. and H.A.A. contributed to the writing. S.T.O. assisted with XRD data collection and interpretation of the data. A.M.S. contributed to discussion and interpretation of the data as well as assisted with experimental setup. H.A.A. supervised the project. All authors reviewed the manuscript. The authors declare no competing financial interests.

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