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Title: Electronic Interactions of Size-Selected Oxide Clusters on Metallic and Thin Film Oxide Supports

Abstract

The interfacial electronic structure of various size-selected metal oxide nanoclusters (M 3O x; M = Mo, Nb, Ti) on Cu(111) and a thin film of Cu 2O supports were investigated in this paper by a combination of experimental methods and density functional theory (DFT). These systems explore electron transfer at the metal–metal oxide interface which can modify surface structure, metal oxidation states, and catalytic activity. Electron transfer was probed by measurements of surface dipoles derived from coverage dependent work function measurements using two-photon photoemission (2PPE) and metal core level binding energy spectra from X-ray photoelectron spectroscopy (XPS). The measured surface dipoles are negative for all clusters on Cu(111) and Cu 2O/Cu(111), but those on the Cu 2O surface are much larger in magnitude. In addition, sub-stoichiometric or “reduced” clusters exhibit smaller surface dipoles on both the Cu(111) and Cu 2O surfaces. Negative surface dipoles for clusters on Cu(111) suggest Cu → cluster electron transfer, which is generally supported by DFT-calculated Bader charge distributions. For Cu 2O/Cu(111), calculations of the surface electrostatic potentials show that the charge distributions associated with cluster adsorption structures or distortions at the cluster–Cu 2O–Cu(111) interface are largely responsible for the observed negative surface dipoles. Changes observedmore » in the XPS spectra for the Mo 3d, Nb 3d, and Ti 2p core levels of the clusters on Cu(111) and Cu 2O/Cu(111) are interpreted with help from the calculated Bader charges and cluster adsorption structures, the latter providing information about the presence of inequivalent cation sites. Finally, the results presented in this work illustrate how the combined use of different experimental probes along with theoretical calculations can result in a more realistic picture of cluster–support interactions and bonding.« less

Authors:
 [1];  [2]; ORCiD logo [2]; ORCiD logo [3]
  1. Stony Brook Univ., NY (United States). Dept. of Chemistry
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). Chemistry Dept.
  3. Brookhaven National Lab. (BNL), Upton, NY (United States). Chemistry Dept.; Stony Brook Univ., NY (United States). Dept. of Chemistry
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1412738
Report Number(s):
BNL-114561-2017-JA
Journal ID: ISSN 1932-7447; R&D Project: CO007; KC0301020; TRN: US1800337
Grant/Contract Number:
SC0012704
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 121; Journal Issue: 40; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Xue, Meng, Nakayama, Miki, Liu, Ping, and White, Michael G. Electronic Interactions of Size-Selected Oxide Clusters on Metallic and Thin Film Oxide Supports. United States: N. p., 2017. Web. doi:10.1021/acs.jpcc.7b07889.
Xue, Meng, Nakayama, Miki, Liu, Ping, & White, Michael G. Electronic Interactions of Size-Selected Oxide Clusters on Metallic and Thin Film Oxide Supports. United States. doi:10.1021/acs.jpcc.7b07889.
Xue, Meng, Nakayama, Miki, Liu, Ping, and White, Michael G. 2017. "Electronic Interactions of Size-Selected Oxide Clusters on Metallic and Thin Film Oxide Supports". United States. doi:10.1021/acs.jpcc.7b07889.
@article{osti_1412738,
title = {Electronic Interactions of Size-Selected Oxide Clusters on Metallic and Thin Film Oxide Supports},
author = {Xue, Meng and Nakayama, Miki and Liu, Ping and White, Michael G.},
abstractNote = {The interfacial electronic structure of various size-selected metal oxide nanoclusters (M3Ox; M = Mo, Nb, Ti) on Cu(111) and a thin film of Cu2O supports were investigated in this paper by a combination of experimental methods and density functional theory (DFT). These systems explore electron transfer at the metal–metal oxide interface which can modify surface structure, metal oxidation states, and catalytic activity. Electron transfer was probed by measurements of surface dipoles derived from coverage dependent work function measurements using two-photon photoemission (2PPE) and metal core level binding energy spectra from X-ray photoelectron spectroscopy (XPS). The measured surface dipoles are negative for all clusters on Cu(111) and Cu2O/Cu(111), but those on the Cu2O surface are much larger in magnitude. In addition, sub-stoichiometric or “reduced” clusters exhibit smaller surface dipoles on both the Cu(111) and Cu2O surfaces. Negative surface dipoles for clusters on Cu(111) suggest Cu → cluster electron transfer, which is generally supported by DFT-calculated Bader charge distributions. For Cu2O/Cu(111), calculations of the surface electrostatic potentials show that the charge distributions associated with cluster adsorption structures or distortions at the cluster–Cu2O–Cu(111) interface are largely responsible for the observed negative surface dipoles. Changes observed in the XPS spectra for the Mo 3d, Nb 3d, and Ti 2p core levels of the clusters on Cu(111) and Cu2O/Cu(111) are interpreted with help from the calculated Bader charges and cluster adsorption structures, the latter providing information about the presence of inequivalent cation sites. Finally, the results presented in this work illustrate how the combined use of different experimental probes along with theoretical calculations can result in a more realistic picture of cluster–support interactions and bonding.},
doi = {10.1021/acs.jpcc.7b07889},
journal = {Journal of Physical Chemistry. C},
number = 40,
volume = 121,
place = {United States},
year = 2017,
month = 9
}

Journal Article:
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  • Size-selected niobium oxide nanoclusters (Nb 3O 5, Nb 3O 7, Nb 4O 7, and Nb 4O 10) were deposited at room temperature onto a Cu(111) surface and a thin film of Cu 2O on Cu(111), and their interfacial electronic interactions and reactivity toward water dissociation were examined. These clusters were specifically chosen to elucidate the effects of the oxidation state of the metal centers; Nb 3O 5 and Nb 4O 7 are the reduced counterparts of Nb 3O 7 and Nb 4O 10, respectively. From two-photon photoemission spectroscopy (2PPE) measurements, we found that the work function increases upon cluster adsorptionmore » in all cases, indicating a negative interfacial dipole moment with the positive end pointing into the surface. The amount of increase was greater for the clusters with more metal centers and higher oxidation state. Additional analysis with DFT calculations of the clusters on Cu(111) indicated that the reduced clusters donate electrons to the substrate, indicating that the intrinsic cluster dipole moment makes a larger contribution to the overall interfacial dipole moment than charge transfer. X-ray photoelectron spectroscopy (XPS) measurements showed that the Nb atoms of Nb 3O 7 and Nb 4O 10 are primarily Nb 5+ on Cu(111), while for the reduced Nb 3O 5 and Nb 4O 7 clusters, a mixture of oxidation states was observed on Cu(111). Temperature-programmed desorption (TPD) experiments with D 2O showed that water dissociation occurred on all systems except for the oxidized Nb 3O 7 and Nb 4O 10 clusters on the Cu 2O film. A comparison of our XPS and TPD results suggests that Nb 5+ cations associated with Nb=O terminal groups act as Lewis acid sites which are key for water binding and subsequent dissociation. TPD measurements of 2-propanol dehydration also show that the clusters active toward water dissociation are indeed acidic. DFT calculations of water dissociation on Nb 3O 7 support our TPD results, but the use of bulk Cu 2O(111) as a model for the Cu 2O film merits future scrutiny in terms of interfacial charge transfer. The combination of our experimental and theoretical results suggests that both Lewis acidity and metal reducibility are important for water dissociation.« less
  • In this report, the effect of incorporation of metallic tin (Sn) on opto-electronic properties of ZnO thin films is presented. ZnO thin films were deposited through ‘automated chemical spray pyrolysis’ (CSP) technique; later different quantities of ‘Sn’ were evaporated on it and subsequently annealed. Vacuum annealing showed a positive effect on crystallinity of films. Creation of sub band gap levels due to ‘Sn’ diffusion was evident from the absorption and PL spectra. The tin incorporated films showed good photo response in visible region. Tin incorporated ZnO thin films seem to satisfy the desirable criteria for buffer layer in thin filmmore » solar cells.« less
  • We investigated the effects of top gate voltage (V{sub TG}) and temperature (in the range of 25 to 70 {sup o}C) on dual-gate (DG) back-channel-etched (BCE) amorphous-indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs) characteristics. The increment of V{sub TG} from -20V to +20V, decreases the threshold voltage (V{sub TH}) from 19.6V to 3.8V and increases the electron density to 8.8 x 10{sup 18}cm{sup −3}. Temperature dependent field-effect mobility in saturation regime, extracted from bottom gate sweep, show a critical dependency on V{sub TG}. At V{sub TG} of 20V, the mobility decreases from 19.1 to 15.4 cm{sup 2}/V ⋅ s with increasingmore » temperature, showing a metallic conduction. On the other hand, at V{sub TG} of - 20V, the mobility increases from 6.4 to 7.5cm{sup 2}/V ⋅ s with increasing temperature. Since the top gate bias controls the position of Fermi level, the temperature dependent mobility shows metallic conduction when the Fermi level is above the conduction band edge, by applying high positive bias to the top gate.« less
  • The physical nature of electronic processes in oxide glassy semiconductors (OGS) based on V/sub 2/O/sub 5/ is discussed on the basis of the theory of the small-radius polaron (SRP). The most important parameters of the process of charge transfer by polarons are determined from an analysis of the temperature dependence of the static conductivity by mathematical modeling employing general theoretical expressions. A model of coupled SRP, presuming that they are localized by the Coulomb field of the charged defect centers, is proposed for describing the complex of data on the effects of a strong electric field and dielectric relaxation. Onmore » the basis of the model expressions describing the dependence of the current density and dielectric constant on the dc electric field strength and also a relation determining the dielectric relaxation time for the given model are obtained. The results of studies of the electric properties of OGS, modified by additions of a second transition-metal oxide, are discussed also.« less
  • Ionic/electronic interaction offers an additional dimension in the recent advancements of condensed materials. Here, lateral gate control of conductivities of indium-zinc-oxide (IZO) films is reported. An electric-double-layer (EDL) transistor configuration was utilized with a phosphorous-doped SiO{sub 2} nanogranular film to provide a strong lateral electric field. Due to the strong lateral protonic/electronic interfacial coupling effect, the IZO EDL transistor could operate at a low-voltage of 1 V. A resistor-loaded inverter is built, showing a high voltage gain of ∼8 at a low supply voltage of 1 V. The lateral ionic/electronic coupling effects are interesting for bioelectronics and portable electronics.