title: Epitaxial NixPd1-x(111) Alloy Substrates with Continuously Tunable Lattice Constants for 2D Materials Growth.
abstract: Epitaxial strain can be a powerful parameter for directing the growth of thin films. Unfortunately, conventional materials only offer discrete choices for setting the lattice strain. In this work, it is demonstrated that epitaxial growth of transition metal alloy solid solutions can provide thermally stable, high-quality growth substrates with continuously tunable lattice constants. Molecular beam epitaxy was used to grow NixPd1-x(111) alloy films with lattice constants between 3.61 and 3.89 Å on the hexagonal (0001) basal planes of α-Al2O3and Cr2O3(grown as epitaxial films on α-Al2O3(0001)). The Cr2O3acted as an adhesion layer, which not only improved the high-temperature stability of the films but also produced single-domain films with NixPd1-x[112̅] parallel to Cr2O3[112̅0], in contrast to growth on α-Al2O3that yielded twinned films. Surface characterization by electron diffraction and scanning tunneling microscopy (STM) as well as bulk X-ray diffraction analysis indicated that the films are suitable as inexpensive and stable substrates for thin-film growth and for surface science studies. To demonstrate this suitability, bilayer SiO2, a two-dimensional van der Waals material, was grown on a NixPd1-x(111) film tuned to closely match the film's lattice constant, with STM and electron diffraction results revealing a highly ordered, single-phase crystalline state.
authors.affiliation: Center for Research on Interface Structures and Phenomena (CRISP), ‡Department of Chemical and Environmental Engineering, and §Department of Mechanical Engineering and Materials Science, Yale University , New Haven, Connecticut 06520, United States.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Hutchings
authors.affiliation: Center for Research on Interface Structures and Phenomena (CRISP), ‡Department of Chemical and Environmental Engineering, and §Department of Mechanical Engineering and Materials Science, Yale University , New Haven, Connecticut 06520, United States.
authors.forename: Jin-Hao
authors.initials: JH
authors.lastname: Jhang
authors.affiliation: Center for Research on Interface Structures and Phenomena (CRISP), ‡Department of Chemical and Environmental Engineering, and §Department of Mechanical Engineering and Materials Science, Yale University , New Haven, Connecticut 06520, United States.
authors.forename: Chao
authors.initials: C
authors.lastname: Zhou
authors.affiliation: Center for Research on Interface Structures and Phenomena (CRISP), ‡Department of Chemical and Environmental Engineering, and §Department of Mechanical Engineering and Materials Science, Yale University , New Haven, Connecticut 06520, United States.
authors.forename: David
authors.initials: D
authors.lastname: Hynek
authors.affiliation: Center for Research on Interface Structures and Phenomena (CRISP), ‡Department of Chemical and Environmental Engineering, and §Department of Mechanical Engineering and Materials Science, Yale University , New Haven, Connecticut 06520, United States.
authors.forename: Udo D
authors.initials: UD
authors.lastname: Schwarz
authors.affiliation: Center for Research on Interface Structures and Phenomena (CRISP), ‡Department of Chemical and Environmental Engineering, and §Department of Mechanical Engineering and Materials Science, Yale University , New Haven, Connecticut 06520, United States.
authors.forename: Eric I
authors.identifier: http://orcid.org/0000-0003-4032-271X
authors.initials: EI
authors.lastname: Altman
keywords: alloy; bilayer silica; molecular beam epitaxy; nickel; palladium; thin-film growth; two-dimensional materials