title: Electron enrichment in 3d transition metal oxide hetero-nanostructures.
abstract: Direct experimental observation of spontaneous electron enrichment of metal d orbitals in a new transition metal oxide heterostructure with nanoscale dimensionality is reported. Aqueous chemical synthesis and vapor phase deposition are combined to fabricate oriented arrays of high-interfacial-area hetero-nanostructures comprised of titanium oxide and iron oxide nanomaterials. Synchrotron-based soft X-ray spectroscopy techniques with high spectral resolution are utilized to directly probe the titanium and oxygen orbital character of the interfacial region's occupied and unoccupied densities of states. These data demonstrate the interface to possess electrons in Ti 3d bands and an emergent degree of orbital hybridization that is absent in parent oxide reference crystals. The carrier dynamics of the hetero-nanostructures are studied by ultrafast transient absorption spectroscopy, which reveals the presence of a dense manifold of states, the relaxations from which exhibit multiple exponential decays whose magnitudes depend on their energetic positions within the electronic structure.
authors.affiliation: Department of Mechanical Engineering, University of California at Berkeley, Berkeley, California 94720, United States.
authors.forename: Coleman X
authors.initials: CX
authors.lastname: Kronawitter
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Bakke
authors.forename: Damon A
authors.initials: DA
authors.lastname: Wheeler
authors.forename: Wei-Cheng
authors.initials: WC
authors.lastname: Wang
authors.forename: Chinglin
authors.initials: C
authors.lastname: Chang
authors.forename: Bonnie R
authors.initials: BR
authors.lastname: Antoun
authors.forename: Jin Z
authors.initials: JZ
authors.lastname: Zhang
authors.forename: Jinghua
authors.initials: J
authors.lastname: Guo
authors.forename: Stacey F
authors.initials: SF
authors.lastname: Bent
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Mao
authors.forename: Lionel
authors.initials: L
authors.lastname: Vayssieres
mesh_terms: D016880:Anisotropy; D003460:Crystallization; D004563:Electrochemistry / Q000379:methods; D004583:Electrons; D005290:Ferric Compounds / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D008670:Metals / Q000737:chemistry; D046529:Microscopy, Electron, Transmission / Q000379:methods; D036103:Nanotechnology / Q000379:methods*; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods; D017356:Synchrotrons; D014025:Titanium / Q000737:chemistry; D014965:X-Rays
chemical_list: D005290:Ferric Compounds; D008670:Metals; D010087:Oxides; C009495:titanium dioxide; C000499:ferric oxide; D014025:Titanium; D010100:Oxygen