title: Amorphous Mixed-Metal Oxide Thin Films from Aqueous Solution Precursors with Near-Atomic Smoothness.
abstract: Thin films with tunable and homogeneous composition are required for many applications. We report the synthesis and characterization of a new class of compositionally homogeneous thin films that are amorphous solid solutions of Al2O3and transition metal oxides (TMOx) including VOx, CrOx, MnOx, Fe2O3, CoOx, NiO, CuOx, and ZnO. The synthesis is enabled by the rapid decomposition of molecular transition-metal nitrates TM(NO3)xat low temperature along with precondensed oligomeric Al(OH)x(NO3)3-xcluster species, both of which can be processed from aq solution. The films are dense, ultrasmooth (Rrms< 1 nm, near 0.1 nm in many cases), and atomically mixed amorphous metal-oxide alloys over a large composition range. We assess the chemical principles that favor the formation of amorphous homogeneous films over rougher phase-segregated nanocrystalline films. The synthesis is easily extended to other compositions of transition and main-group metal oxides. To demonstrate versatility, we synthesized amorphous V0.1Cr0.1Mn0.1Fe0.1Zn0.1Al0.5Oxand V0.2Cr0.2Fe0.2Al0.4Oxwith Rrms≈ 0.1 nm and uniform composition. The combination of ideal physical properties (dense, smooth, uniform) and broad composition tunability provides a platform for film synthesis that can be used to study fundamental phenomena when the effects of transition metal cation identity, solid-state concentration of d-electrons or d-states, and/or crystallinity need to be controlled. The new platform has broad potential use in controlling interfacial phenomena such as electron transfer in solar-cell contacts or surface reactivity in heterogeneous catalysis.
authors.affiliation: Department of Chemistry and Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403, United States.
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Kast
authors.affiliation: Department of Chemistry and Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403, United States.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Cochran
authors.affiliation: Department of Chemistry and Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403, United States.
authors.forename: Lisa J
authors.initials: LJ
authors.lastname: Enman
authors.affiliation: Department of Chemistry and Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403, United States.
authors.forename: Gavin
authors.identifier: 0000-0002-0840-2376
authors.initials: G
authors.lastname: Mitchson
authors.affiliation: Department of Chemistry and Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403, United States.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Ditto
authors.affiliation: Department of Chemistry and Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403, United States.
authors.forename: Chris
authors.initials: C
authors.lastname: Siefe
authors.affiliation: Department of Chemistry and Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403, United States.
authors.forename: Paul N
authors.initials: PN
authors.lastname: Plassmeyer
authors.affiliation: Department of Chemistry and Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403, United States.
authors.forename: Ann L
authors.initials: AL
authors.lastname: Greenaway
authors.affiliation: Department of Chemistry and Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403, United States.
authors.forename: David C
authors.initials: DC
authors.lastname: Johnson
authors.affiliation: Department of Chemistry and Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403, United States.
authors.forename: Catherine J
authors.identifier: 0000-0002-4545-7835
authors.initials: CJ
authors.lastname: Page
authors.affiliation: Department of Chemistry and Biochemistry and the Materials Science Institute, University of Oregon , Eugene, Oregon 97403, United States.
authors.forename: Shannon W
authors.identifier: 0000-0001-8971-9123
authors.initials: SW
authors.lastname: Boettcher