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AVS

Materials for Energy MeetingSeptember 6, 2012

Powered by the AVS Prairie Chapter

University of Illinois at Urbana-Champaign

Frederick Seitz Materials Research Laboratory

Program and Abstracts

University of Illinois at Urbana-ChampaignFrederick Seitz Materials Research Laboratory104 South Goodwin AvenueUrbana, IL 61801

2012 AVS Materials for Energy Program and Local Arrangements Committee Jerry Moore, AVS Prairie Chapter Chair Richard Haasch, University of Illinois Chris Johns, University of Illinois Mauro Sardela, University of Illinois Julio Soares, University of Illinois Timothy Spila, University of Illinois

AVS Prairie Chapter Executive Committee

Jerry Moore (Chair), MassThink Michael Trenary (Vice-Chair), University of Illinois – Chicago Seth Darling (Past Chair), Argonne National Laboratory Hans Luedi (Treasurer), Midwest Vacuum Bob Campbell (Secretary), Norlux Yip-Wah Chung, Northwestern University David Czaplewski, Argonne National Laboratory Scott Dix, Vacuum One Paul Lyman, University of Wisconsin Chris McCarthy, Oerlikon Leybold Vacuum Jessica McChesney, Argonne National Laboratory Richard Rosenberg, Argonne National Laboratory Allan Rowe, Fermi National Accelerator Laboratory Julio Soares, University of Illinois

Sponsors

AVS Prairie Chapter

Greetings! On behalf of the AVS Prairie Chapter, the Frederick Seitz Materials Research Laboratory, and the University of Illinois at Urbana-Champaign AVS Student Chapter, we welcome you to the 2012 AVS Materials for Energy Meeting. The focus topic for this year’s meeting, “Materials for Energy” is a topic that has been attracting great attention in the last few years. As energy needs continue to grow worldwide, our conventional energy sources become strained and new materials and methods for a more efficient generation, storage, transport, and conversion of energy are essential to meet future demand. This field is thus of extreme economical and strategic importance. This year we have put an exciting program together that exemplifies the outstanding research in the field, with 4 plenary talks, 11 contributed oral presentations and 13 posters on materials for energy and other topics of great interest to the AVS community.

We also are honored to present the second AVS Prairie Chapter Outstanding Research Award to Professor Steven J. Sibener from University of Chicago, who will open our meeting with his talk Interfacial Structure, Dynamics and Reactivity of Advanced Materials Examined with Molecular Beam Scattering, Scanning Probe Imaging, and Numerical Simulations

We are very grateful for the support offered by our corporate exhibitors to this event. Representatives of 12 companies will be present, displaying the newest instruments and technologies at the Sponsors Exhibition. They are ready to help with your instrumentation and supply needs and questions. Please make sure you don’t miss the opportunity to visit the exhibition.

Thank you for your participation and contribution to the 2012 AVS Materials for Energy Meeting.

Thanks to all who contributed to enable this outstanding program.

The 2012 AVS Materials for Energy Meeting program committee.

Reception and Best Student Poster Presentation Award Ceremony

Please join us at 5:20, after the last oral presentation, for the closing ceremony, where we will present and celebrate this year’s winners of our top three Best Student Poster Presentation Awards, with wine, beer, cheese, soft drinks, and snacks.

Wine, Beer, Cheese,

etc.

5:20 p.m.

Twin Groves Wind Farm located in Eastern McLean County IL, consists of 240 Vesta 1.65 MW wind turbines having a total capacity of 398 MW. The site produces approximately 1.3 billion kilowatt hours annually, enough electricity to power 120,000 homes.

Materials for Energy AVS Prairie Chapter Annual Meeting

Thursday, September 6, 2012

Exhibitors

Agilent Technologies

Alan Burrill Technical Sales

BellowsTech, LLC

Control Plus Inc

DMS

HORIBA Scientific

Midwest Vacuum, Inc.

Nanophoton Corp.

Oerlikon Leybold Vacuum USA

Starr Vacuum Co.

Thermo Scientific

Vacuum One

AVS Prairie Chapter 2012 Materials for Energy Meeting

Thursday, September 6, 2012

8:30 Registration and Continental Breakfast

Invited talks – Room 190 ESB Chair: Jerry Moore, AVS Prairie Chapter

9:00 AVS Prairie Chapter Outstanding Research Award Lecture

Steven J. Sibener, University of Chicago Interfacial Structure, Dynamics and Reactivity of Advanced Materials Examined with Molecular Beam Scattering, Scanning Probe Imaging, and Numerical Simulations

9:40 Lane Martin, University of Illinois at Urbana-Champaign

Next Generation Energy Materials: Challenges in Controlling Complex Oxides for Advanced Applications

10:20 Coffee Break in the MRL Hall with exhibitors

10:40 Rakesh Agrawal, Purdue University

Thin Film Solar Cells from Nanocrystal Inks of Quaternary Chalcogenides

11:20 Daniel Abraham, Argonne National Laboratory Overcoming Materials Challenges Facing Lithium-Ion Batteries

12:00 AVS Prairie Chapter lunch and business meeting (open to all)

Contributed Talks – Room 190 ESB

Moderator: Mauro Sardela, Materials Research Laboratory

1:00 Sungki Lee, University of Illinois at Urbana-Champaign Enhanced Photocatalysis from Anomalous Light Absorption and Quantization in SrRuO3

1:20 Iradwikanari Waluyo, University of Illinois at Chicago

Surface Chemistry and Intermediates of Ethylamine on Pt(111)

1:40 Vinod K. Sangwan, Northwestern University Dielectric Breakdown Study for High Performance, Reliable Top-gated Large-area Graphene Electronics

2:00 TeYu Chien, Northwestern University

Adsorption and Desorption of Hydrogen on Epitaxial Graphene on SiC(0001): An Ultra-High Vacuum Scanning Tunneling Microscopy Study

2:20 Brent A. Apgar, University of Illinois at Urbana-Champaign

Deterministic Control of Reduction and Oxidation Reaction Locations on TiO2-capped BiFeO3 Thin Films

2:40 Coffee break and poster presentations in the MRL Hall with exhibitors

Contributed Talks – Room 190 ESB

Moderator: Tim Spila, Materials Research Laboratory

3:20 A. B. Mei, University of Illinois at Urbana-Champaign Composition, Nanostructure, and Properties of Epitaxial Zr1-xAlxN/MgO(001) Alloys and Zr1-xAlxN/ZrN(001) Superlattices Grown from a Single Zr0.75Al0.25 Target by Reactive Magnetron Sputtering

3:40 Sergey V. Baryshev, Argonne National Laboratory

Understanding Atomic-Layer-Deposition Synthesis of Cu2ZnSnS4 Solar Cells

4:00 Andrei Kolmakov, Southern Illinois University at Carbondale Photoelectron and Electron Spectro-Microscopy in Liquids and Dense Gaseous Environment Using Electron Transparent Membranes

4:20 Hadi Tavassol, University of Illinois at Urbana-Champaign

Interfacial Processes in Li-ion Battery Anodes

4:40 Alan D. Feinerman, University of Illinois at Chicago Vacuum Insulation Panels with Tensile Supports to increase the Energy Efficiency of a Building’s Envelope

5:00 Kedar Manandhar, University of Illinois at Chicago

Surface Chemistry of the Adsorption and Decomposition of NH3 and Ga(CH3)3 on the ZrB2(0001) Surface

5:20 Closing remarks, poster awards and reception (wine and appetizers)

Interfacial Structure, Dynamics and Reactivity of Advanced

Materials Examined with Molecular Beam Scattering, Scanning Probe Imaging, and Numerical Simulations

Steven J. Sibener1

1The James Franck Institute and Department of Chemistry, The University of Chicago, Gordon Center for Integrative Science, 929 East 57th Street, Chicago, IL 60637 USA

This presentation will examine current forefront topics in interfacial structure, dynamics, and reactivity. Notable advances are occurring in our atomic-level view of such issues, driven by synergies between scattering measurements, local scanning probe imaging, numerical simulations and theory. Emphasis is increasingly aimed at examining how local structures kinetically form on the atomic level [1-3], and how relative reactivity and physical properties depend on local ensemble configuration. Another trend is the examination of more complex interfaces including structural evolution on multiple length-scales. Examples of this include self-assembling molecular systems [4], polymers [5,6], and hierarchical functional materials [7,8]. Due to the aforementioned developments, we are gaining rigorous atomic-level insight into the dynamical processes which govern a wide-range of heterogeneous phenomena, such as reaction dynamics and catalysis [9], collisional energy transfer [10], materials growth and erosion, self-organization, and interfacial metallurgy. This presentation will illustrate the above using recent research from our laboratory. It is with the greatest pleasure that I acknowledge as part of this award address all past and present members of the Sibener Group whose beautiful science contributed to these accomplishments. [1] Time-Resolved AFM Imaging Studies of Asymmetric PS-b-PMMA Ultrathin Films: Dislocation and Disclination Transformations, Defect Mobility, and Evolution of Nanoscale Morphology, J. Hahm and S. J. Sibener, J. Chem. Phys. 114, 4730-4740 (2001). [2] Spatial and Temporal Dynamics of Individual Step Merging Events on Ni(977) Measured by STM, T.P. Pearl, S.J. Sibener, J. Phys. Chem. B 105, 6300-6306 (2001). [3] Dynamics of Molecular and Polymeric Interfaces Probed with Atomic Beam Scattering and Scanning Probe Imaging, Ryan D. Brown, Qianqian Tong, James S. Becker, Miriam A. Freedman, N. A. Yufa, and S. J. Sibener, Faraday Discussion 157; In Press (2012). [4] Chiral Domains Achieved by Surface Adsorption of Achiral Nickel Tetraphenyl- or Octaethylporphyrin on Smooth and Locally Kinked Au(111), Lieve G. Teugels, L. Gaby Avila-Bront, and S.J. Sibener, J. Phys. Chem. C 115, 2826-2834 (2011). [5] Atomic Scattering as a Probe of Polymer Surface and Thin Film Dynamics, M. A. Freedman, A. W. Rosenbaum, and S. J. Sibener, Phys. Rev. B, 75, 113410/1-4 (2007). [6] Comparative Surface Dynamics of Amorphous and Semicrystalline Polymer Films, James S. Becker, Ryan D. Brown, Daniel R. Killelea, Hanqiu Yuan, and S. J. Sibener, Proceedings of the National Academy of Sciences 108, 977-982 (2011). [7] Improved Hybrid Solar Cells via In Situ UV-Polymerization, Sanja Tepavcevic, Seth B. Darling, Nada Dimitrijevic, Tijana Rajh, and S. J. Sibener, Small 5, 1776-1783 (2009). [8] He Atom Diffraction Measurements of the Surface Structure and Vibrational Dynamics of CH3-Si(111) and CD3-Si(111) Surface, James S. Becker, Ryan D. Brown, Erik Johansson, Nathan S. Lewis, and S. J. Sibener, J. Chem. Phys. 133, 104705/1-8 (2010). [9] Applied Reaction Dynamics: Efficient Synthesis Gas Production via Single Collision Partial Oxidation of Methane to CO on Rh(111), K. D. Gibson, M. Viste, and S. J. Sibener, J. Chem. Phys., 125, 133401 (2006). [10] Scattering of High-Incident-Energy Kr and Xe from Ice: Evidence That a Major Channel Involves Penetration into the Bulk, K. D. Gibson, Daniel R. Killelea, Hanqiu Yuan, James S. Becker, Subha Pratihar, Paranjothy Manikandan, Swapnil C., Kohale, W. L. Hase, and S. J. Sibener, J. Phys. Chem. C, 116, 14264-14273 (2012).

Next Generation Energy Materials: Challenges in Controlling Complex Oxides for Advanced Applications

Lane W. Martin1

1Department of Materials Science and Engineering and Material Research Laboratory, University of

Illinois, Urbana-Champaign, Urbana, IL 61801 (USA), Complex oxide materials are increasingly being considered for next-generation electronic and energy applications which is driving the community to rapidly develop new modalities and deeper understanding of the complex interplay of processing, chemistry, and properties in these materials. Here we will discuss advances in controlling complex oxide materials with a precision that approaches that historically reserved for semiconductor systems. We will highlight work on SrTiO3 and LaAlO3/SrTiO3 systems where challenges in controlling the cation stoichiometry of these materials can have dramatic impact on the structure and properties. The implications of variations cation stoichiometry for the crystal structure, dielectric, thermal, and electronic properties will be reviewed. In particular, we will examine how non-stoichiometry can lead to asymmetric property evolution and how even relatively small variations in cation chemistry can result in large effects – such as changes in interfacial conductance in excess of 7 orders-of-magnitude. Overall we will demonstrate a strong link between the growth process, the stoichiometry of the resulting materials, the desired properties of the system, and the implications for understanding the physics and how to engineer these materials.

Thin Film Solar Cells from Nanocrystal Inks of Quaternary Chalcogenides

Rakesh Agrawal1

1School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA

The creation of a suitable inorganic colloidal nanocrystal ink for use in a scalable coating process is a key step in the development of low-cost thin film solar cells. We have developed an innovative method of using copper indium gallium disulfide (CIGS) nanocrystals as the building block for the fabrication of bulk CIGSSe thin films. The CIGS nanocrystal ink solution is applied directly on various substrates to form a thin film coating. The CIGS nanocrystals are then consolidated into large crystalline chalcopyrite domains by a brief thermal treatment under Se vapor. Furthermore, the ability to control the composition for CIGS nanocrystals allows the unique capability to bandgap engineer the CIGSSe absorber using nanocrystals with different ratios of In/Ga. By optimizing processing conditions for the various layers in the solar cells, total area efficiency of 14.2% under AM1.5 illumination has been achieved.

Our scouting experiments based on the adaptation of CIGS method has also resulted in Cu2ZnSnS4 (CZTS) nanocrystals and the associated PV devices.Although the solar cell performance of the currently fabricated solar cells is somewhat low (total area power conversion efficiencies in the range of 8.3% to 9.3%), the results are very promising and investigation is underway to improve their chemical and structural properties.

Overcoming Materials Challenges Facing Lithium-Ion Batteries

Daniel P. Abraham1

1Argonne National Laboratory For lithium-ion batteries to widely power plug-in hybrid electric and all-electric vehicles (PHEVs and EVs), they must meet a range of stringent criteria: sufficient energy densities to allow for more than 100 miles of travel on a single charge, in addition to moderate, but consistent, power densities. Batteries should also be able to endure a ~10 year calendar-life and sustain up to several thousand charge and discharge cycles. Inexpensive battery packs, as well as their safe operation are additional key requirements for successful technology adoption. To overcome these challenges, various lithium-ion battery chemistries, including positive electrodes containing oxide and phosphate compounds, negative electrodes containing graphite and silicon materials, and electrolytes containing various salts and additives are been examined. Batteries containing lithium- and manganese-rich transition metal layered-oxides (LMR-NMC) positive materials can theoretically deliver energy densities more than twice that of commercial LiCoO2-based batteries. However, the above life requirements cannot be met by conventional LMR-NMC-containing batteries; rising internal resistances and continuous loss of capacity lower the amount of recoverable energy from cycle to cycle. Strategies to overcome these limitations through modifications to the materials and electrodes will be discussed in this presentation.

Oral Presentations

1. Sungki Lee1,2, Brent A. Apgar1,2, Lauren Schroeder1,2, and Lane W. Martin1,2


2. Iradwikanari Waluyo, Joel D. Krooswyk, Jun Yin, Yuan Ren and Michael Trenary Enhanced Photocatalysis from Anomalous Light Absorption and Quantization in SrRuO3

3. Vinod K. Sangwan1, Deep Jariwala1, Stephen A. Filippone2, Hunter J. Karmel1, James E. Johns1,4, Justice M.P. Alaboson1, Tobin J. Marks1,3, Lincoln J. Lauhon1, Mark C. Hersam1,3,4

Dielectric Breakdown Study for High Performance, Reliable Top-gated Large-area Graphene Electronics

4. TeYu Chien1, Chung-Hong Sham1, and Mark C. Hersam1,2,3

Adsorption and Desorption of Hydrogen on Epitaxial Graphene on SiC(0001): An Ultra-High Vacuum Scanning Tunneling Microscopy Study

5. Brent A. Apgar1, Lane W. Martin1,2


6. A. B. Mei,1 B. M. Howe,2 H. Fager,3 N. Ghafoor,3 E. Broitman, 3 M. Sardela,1 A. Shah,1 M. Oden, 3

L. Hultman, 3 A. Rockett,1 J. E. Greene,1 and I. Petrov,1

Composition, Nanostructure, and Properties of Epitaxial Zr1-xAlxN/MgO(001) Alloys and Zr1-

xAlxN/ZrN(001) Superlattices Grown from a Single Zr0.75Al0.25 Target by Reactive Magnetron Sputtering

7. Sergey V. Baryshev*, Elijah Thimsen+, Shannon C. Riha, Alex B.F. Martinson, Jeffrey W. Elam, Michael J. Pellin, Igor V. Veryovkin * Understanding Atomic-Layer-Deposition Synthesis of Cu2ZnSnS4 Solar Cells

8. Mark Krueger1, Joshua Stoll1, Dmitriy A. Dikin2, Laura J. Cote2, Jiaxing Huang2, Majid Kazemian Abyaneh3, Matteo Amati3, Luca Gregoratti3, Sebastian Günther4, Maya Kiskinova3 and Andrei Kolmakov1

Photoelectron and Electron Spectro-Microscopy in Liquids and Dense Gaseous Environment Using Electron Transparent Membranes

9. Hadi Tavassol1, Maria Chan3, Maria Catarello1, Jeffrey Greeley3, David G. Cahill2, Andrew A. Gewirth1


10. Alan D. Feinerman1,2, P. Gupta1, T. Dankovic2, and David W. Yarbrough3

Vacuum Insulation Panels with Tensile Supports to Increase the Energy Efficiency of a Building’s Envelope

11. Kedar Manandhar1, Weronika Walkosz2, Michael Trenary1, and Peter Zapol2



Iradwikanari Waluyo, Joel D. Krooswyk, Jun Yin, Yuan Ren and Michael Trenary

Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607 The identification of the intermediate species formed in a surface-catalyzed reaction is crucial in the fundamental understanding of heterogeneous catalysis. An important reaction with wide implications in the chemical industry is the dehydrogenation of amines to form nitriles. Reflection absorption infrared spectroscopy (RAIRS), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations were used to characterize and identify the surface intermediates and desorption products from the thermal decomposition of ethylamine (CH3CH2NH2) on Pt(111). Ethylamine molecularly adsorbs on Pt(111) at 85 K and remains stable up to 300 K. It partially dehydrogenates upon heating to 330 K, forming a stable surface intermediate with a characteristic RAIR spectrum that indicates the presence of an intact NH2 group and a C-N bond. Vibrational analysis calculations using DFT revealed aminovinylidene (CCHNH2) as the surface intermediate with a delocalized bond across its CCN unit. This finding is confirmed by comparing the experimental and simulated IR spectra of the 15N and D-labeled species. TPD data indicate that this intermediate desorbs as acetonitrile. Upon further heating to 420 K, a second surface intermediate is formed, still with an intact NH2 group and a C-N bond. However, the exact structure of this intermediate is yet to be determined. At temperatures above 500 K, HCN is found to be the only desorption product.

Enhanced Photocatalysis from Anomalous Light Absorption and Quantization in SrRuO3

Sungki Lee1,2, Brent A. Apgar1,2, Lauren Schroeder1,2, and Lane W. Martin1,2

1Department of Materials Science and Engineering and Material Research Laboratory, University of

Illinois, Urbana-Champaign, Urbana, IL 61801 (USA), 2International Institute for Carbon Neutral Energy Research, 744 Motooka, Nishi-ku, Fukuoka 819-0395,

Japan Correlated electron oxides provide a diverse landscape of exotic materials’ phenomena and properties. One example of such a correlated oxide material is strontium ruthenate (SrRuO3) which is known to be a metallic itinerant ferromagnet, to exhibit so-called bad metal behavior at high temperatures (while being a Fermi liquid at low temperatures), and is known for its widespread utility as a conducting electrode in many complex oxides heterostructures. We have observed that the complex electronic structure of SrRuO3 is also responsible for unexpected optical properties including high absorption across the visible spectrum (commensurate with a low band gap semiconductor) and remarkably low reflection compared to traditional metals. By coupling this material to a traditional wide band gap semiconductor (TiO2) via epitaxial growth we have demonstrated the ability to produce dramatically enhanced visible light absorption and resulting large photocatalytic activities. The devices function by photo-excited hot carrier injection from the SrRuO3 to the TiO2 and the effect is enhanced in thin films due to electronic structure changes that promote more efficient charge injection. This observation provides an exciting new approach to the challenge of designing visible-light photosensitive materials.

Dielectric Breakdown Study for High Performance, Reliable Top-gated Large-area Graphene Electronics

Vinod K. Sangwan1, Deep Jariwala1, Stephen A. Filippone2, Hunter J. Karmel1, James E. Johns1,4, Justice

M.P. Alaboson1, Tobin J. Marks1,3, Lincoln J. Lauhon1, Mark C. Hersam1,3,4

1Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, 2Department of Materials Science and Engineering, John Hopkins University, Baltimore,

MD, 21218, 3Department of Chemistry, Northwestern University, Evanston, Illinois 60208, 4Department of Medicine, Northwestern University, Evanston, Illinois 60208

An ultra-thin top-gate dielectric is essential for high-performance large-scale digital and analog electronics based on graphene field-effect transistors (G-FETs). Atomic layer deposition (ALD) has been utilized to grown top-gate dielectrics for high-performance G-FETs. However, ALD requires a seeding layer – often up to 10 nm thick – on the chemically inert graphene surface. Moreover, large-area uniformity and reliability of top-gate dielectrics have not yet been characterized. Here, we show that a single monolayer of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) film can serve as a robust seeding layer for 8 nm thick Al2O3 as the top-gate dielectric in G-FETs with mobilities up to 3000 cm2/Vs. For the first time, we address the issue of large-area uniformity by conducting an industry-standard statistical analysis of top-gate dielectric breakdown. To this end, metal-insulator-semiconductor (MIS) capacitors (area = 20 µm x 20 µm) were fabricated on 10 nm thick Al2O3 over a 0.9 cm x 0.45 cm area of epitaxial graphene grown on n-doped SiC substrates. As expected for an ultra-thin dielectric, we observe that the distribution of breakdown voltage fits well to a Weibull distribution. The dielectric breakdown is characterized by a sudden catastrophic rise in current. The shape parameter (indicating distribution width) and scale parameter (where 63% devices fail) of the distribution are calculated to be 37.64 [95% confidence bounds 31.59-44.84] and 8.92 V [95% confidence bounds 8.86-8.98], respectively, from measurements of 70 capacitors. Overall, this study of dielectric breakdown highlights the critical issue of device reliability that will become increasingly important as graphene moves from research laboratories to commercial applications.

Adsorption and Desorption of Hydrogen on Epitaxial Graphene on SiC(0001): An Ultra-High Vacuum Scanning Tunneling Microscopy

Study

TeYu Chien1, Chung-Hong Sham1, and Mark C. Hersam1,2,3

1Department of Materials Science and Engineering, Northwestern University, Evanston IL 60208

2Department of Chemistry, Northwestern University, Evanston, IL 60208 3Department of Medicine, Northwestern University, Evanston, IL 60208

With superlative physical, chemical, and electronic properties, graphene shows significant promise

in a variety of technologies, including transistors, sensors, and energy conversion/storage devices. However, as an atomically thin material, graphene is highly sensitive to its environment, which implies that surface/interface chemistry must be carefully considered when integrating graphene into functional devices. Towards this end, we have been studying a variety of methods for chemically functionalizing graphene including organic self-assembled monolayers [1] and epoxidation with atomic oxygen [2]. Among possible covalent modification schemes, hydrogenation is arguably the simplest and thus well suited for fundamental atomic-scale studies.

Here, we present an ultra-high vacuum (UHV) scanning tunneling microscopy (STM) study of adsorption and desorption of atomic hydrogen on monolayer and bilayer epitaxial graphene on SiC(0001). Atomic-resolution imaging reveals no measurable differences between the adsorption of atomic hydrogen on monolayer compared to bilayer graphene. At high coverages, the fully hydrogenated graphene surface exhibits a periodicity that is well correlated with the underlying Moiré pattern. The desorption temperature, at which 90% of the hydrogen has desorbed, is observed to be ~120ºC for both monolayer and bilayer graphene. However, at lower temperatures, the desorption rate from bilayer graphene is found to be slightly higher than monolayer graphene, thus suggesting that the underlying substrate can influence reaction kinetics on graphene.

Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Science, under Contract No. DE-AC02-06CH11357. [1] Md. Z. Hossain, et al., “Chemically homogeneous and thermally reversible oxidation of epitaxial

graphene,” Nature Chemistry, 4, 305 (2012). [2] Q. H. Wang and M. C. Hersam, “Room-temperature molecular-resolution characterization of self-assembled organic monolayers on epitaxial graphene,” Nature Chemistry, 1, 206 (2009).


Brent A. Apgar1, Lane W. Martin1,2

1Department of Materials Science and Engineering, and 2Materials Research Laboratory, University of

Illinois, Urbana-Champaign, Urbana, Illinois 61801, USA Critical considerations in designing efficient materials for solar water-splitting are high absorption of visible light, the spatial separation of the reduction and oxidation sites, and the minimization of electron-hole recombination. Some success in achieving these requirements has been seen in complex layered-oxide materials and by using co-catalysts, both of which achieve charge- and reaction-separation, but very few such compounds possess band gaps small enough to be useful under solar illumination. In comparison to these bottom-up processes, we demonstrate an alternative, top-down approach, using a single material to absorb visible light, separate charge, and drive spatially separated reduction and oxidation reactions. BiFeO3 is a multiferroic oxide having a direct band gap of 2.7 eV and a spontaneous polarization of ~90 μC/cm2. Epitaxial thin films of BiFeO3 capped with a very thin layer of anatase TiO2 were grown by pulsed-laser deposition and characterized by X-ray diffraction (XRD), atomic and piezoresponse force microscopy (AFM-PFM), and scanning electron microscopy. Firstly, we observe the inhibition of photodegradation of the BiFeO3 in pure water when capped with anatase TiO2. Second, using PFM we demonstrate the ability to deterministically write up- and down-polarized domains in the BiFeO3 through the TiO2 layer. Lastly, using simulated AM1.5 spectrum illumination we perform photo-deposition experiments of Ag and PbO2 from salt solutions and show preferential photo-reduction on the down-polarized regions and photo-oxidation on the up-polarized regions. The deposition of Ag and PbO2 was confirmed by energy dispersive X-ray spectroscopy (EDS) and XRD, and the rate of deposition was quantified by AFM. This top-down, deterministic control of the reduction and oxidation reaction sites can be used to produce spatially separated hydrogen and oxygen evolution reactions, thereby eliminating the need for post-production separation of the product gases.

Composition, Nanostructure, and Properties of Epitaxial Zr1-xAlxN/MgO(001) Alloys and Zr1-xAlxN/ZrN(001) Superlattices Grown

from a Single Zr0.75Al0.25 Target by Reactive Magnetron Sputtering

A. B. Mei,1 B. M. Howe,2 H. Fager,3 N. Ghafoor,3 E. Broitman, 3 M. Sardela,1 A. Shah,1 M. Oden, 3

L. Hultman, 3 A. Rockett,1 J. E. Greene,1 and I. Petrov,1 1 Department of Materials Science and the Materials Research Laboratory

University of Illinois, 104 South Goodwin, Urbana, IL 61801

Single-phase epitaxial metastable Zr1-xAlxN/MgO(001) (x ≤ 0.25) thin films and Zr1-xAlxN/ZrN(001) superlattices are grown at 650°C by ultra-high vacuum magnetically-unbalanced reactive magnetron sputtering from a single Zr0.75Al0.25 target. The AlN concentration x is controlled by varying the ion energy (5 < Ei < 55 eV) incident at the growth surface while maintaining the ion-to-metal flux ratio constant at Ji/JMe = 8. The net incorporated Al flux JAl decreases from 3.4 to 1.1×1014 atoms cm-2s-1 , due to efficient forward resputtering of deposited Al atoms (27 amu) by Ar+ ions (40 amu) neutralized and backscattered from heavy Zr atoms (91.2 amu). High-resolution x-ray diffraction θ-2θ scans, reciprocal lattice maps, and selected-area electron diffraction revealed that all films are NaCl structure with a cube-on-cube orientation relative to the substrate, (001)Zr1-xAlxN||(001)MgO; the relaxed alloy lattice parameter varies from 0.458 with x = 0.25 to 0.450 nm with x = 0.01. Nanoindentation measurements show that hardness decreases from 28.6 to 23.3 GPa, while the elastic modulus increases from 263 to 296.8 GPa, as x is varied from 0 to 0.25. Z-contrast scanning transmission electron microscopy and nanobeam electron diffraction reveal the presence of a spinodal nanostructure for alloy films with x > 0.18, with a constant characteristic lattice modulation period of 1.1 nm. The hardness H of Zr0.75Al0.25N/ZrN(001) superlattices with equi-thick layers ranges from 27 GPa with bilayer period Λ = 9.2 nm to a maximum of 29 GPa at Λ = 2.3 nm.

Understanding Atomic-Layer-Deposition Synthesis of Cu2ZnSnS4 Solar Cells

Sergey V. Baryshev*, Elijah Thimsen+, Shannon C. Riha,

Alex B.F. Martinson, Jeffrey W. Elam, Michael J. Pellin, Igor V. Veryovkin *[email protected], [email protected]

Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439

Cu2ZnSnS4 (CZTS) has recently attracted attention as a light absorber for photovoltaic applications

because of its band gap (εg≈1.4 eV), the relative abundance and low cost of its constituent elements (which permits large-scale low-cost module production), and its demonstrated solar-to-electricity power conversion efficiencies over 8% [1].

While many materials have been synthesized by atomic layer deposition (ALD), the application of this method to technologically important metal sulfides is underexplored, and homogeneous quaternary metal sulfides are absent from the literature. We outline a first-to-date ALD process to synthesize CZTS [2], in which a trilayer stack of binary metal sulfides (i.e., Cu2S, SnS2 and ZnS) was deposited and mixed by thermal annealing. Since this ALD route relies on the facile solid state diffusion of chalcogenides for mixing we investigate (i) intermixing in the initial stack |substrate/Cu2S/SnS2/ZnS| and (ii) effect of the annealing temperature. The first case is of fundamental interest, while the second one provides parameters needed to fully mix the binaries into a homogenous CZTS alloy.

The composition profiles were measured by time-of-flight secondary ion mass spectrometry in high resolution dual-beam regime (gentleDB TOF SIMS) [3] for both as-deposited trilayer stacks (at 135 C) and after their annealing at elevated temperatures (275, 350 and 425 C) in argon ambient for 60 min. Diffuse interfaces between layers were found in the as-deposited case, indicating that binaries greatly premixed at the synthesis temperature of 135 C. By using high-resolution SIMS depth profiles we were able to estimate roughly the diffusion coefficients between adjunct layers in the trilayer stack (see the table).

Mobile species Matrix in which diffusion occurs D (nm2×s-1)

Cu+ SnS2 5.3×10-3

Sn4+ Cu2S 5.3×10-3

Zn2+ SnS2 3.4×10-3

Sn4+ ZnS < 8.4×10-5

Under annealing, gentleDB SIMS results suggest that mixing of the metal-sulfide binaries into CZTS obeys the following predicted mechanism [4]:

(1) ZnSSnSCuSnSSCu 3222 +→+ ; (2) 4232 ZnSnSCuZnSSnSCu →+ ,

where the step (2) limits the overall solid-state reaction. Particularly, it explains why CZTS forms only at elevated temperatures in excess of 400 C (Cu and Sn concentrations homogenize at much lower temperatures) as was previously evidenced by Raman spectroscopy and X-ray diffraction [2]. Temperature of 425 C was found to be sufficient to fully mix the binaries. One can consider it as a starting point for further device performance-driven process optimization in this ALD route to the CZTS system. Acknowledgements: DOE under DE-AC02-06CH11357, EERE-Solar Energy Technologies Program under FWP-4913A, NASA under NNH08AH76I & NNH09AM48I [1] B. Shin et al. Prog. Photovoltaics: Res. Appl. DOI: 10.1002/pip.1174 (2011) [2] E. Thimsen et al. Chem. Mater. DOI: 10.1021/cm3015463, article ASAP (2012) [3] S.V. Baryshev et al. Rapid Commun. Mass Spectrom. 26, 2224 (2012) [4] F. Hergert and R. Hock. Thin Solid Films 515, 5953 (2007)

mailto:[email protected]

mailto:[email protected]

Photoelectron and Electron Spectro-Microscopy in Liquids and Dense Gaseous Environment Using Electron Transparent Membranes

Mark Krueger1, Joshua Stoll1, Dmitriy A. Dikin2, Laura J. Cote2, Jiaxing Huang2,

Majid Kazemian Abyaneh3, Matteo Amati3, Luca Gregoratti3, Sebastian Günther4, Maya Kiskinova3 and Andrei Kolmakov1

1Southern Illinois University, Carbondale, Illinois 62901, USA

2Northwestern University, Evanston, Illinois 60208, USA 3Sincrotrone Trieste 34012 Trieste, Italy

4TU München, Chemie Department, Lichtenbergstr. 4, D-85748 Garching, Germany Novel bottom-up designed materials currently constitute the major source of innovations in electronics, optics, energy harvesting/storage, catalysis and bio-medical applications. The performance of these new materials and devices depends on physicochemical processes taking place at the interface between the material the environment (i.e. electrolyte, water, air, blood plasma etc). Understanding and tuning the surface properties and performance of these materials requires in situ spectroscopic access to interfacial processes under operando conditions at their natural length scales. Here, we demonstrate the capability to perform XPS (X-ray Photoelectron Spectroscopy) and SEM scanning electron microscopy through graphene based membranes that are only few layers thin and molecularly impenetrable. Different from standard environmental XPS and SEM our approach is based on the recent developments in fabrication and transfer of ultrathin (~1 nm) membranes, such as GO or graphene sheets with thicknesses comparable to the effective attenuation length (EAL) of 200-1000 eV electrons.


Hadi Tavassol1, Maria Chan3, Maria Catarello1, Jeffrey Greeley3, David G. Cahill2, Andrew A. Gewirth1

1Department of Chemistry, 2Department of Materials Science and Engineering, University of Illinois, 3Argonne National Laboratory

During Li+ transport, in Li-ion batteries, a solid electrolyte inter-phase (SEI) composed of breakdown products from the electrode, the solvent, and the electrolyte, forms on both cathode and anode electrode surfaces. Solvents, electrolytes, and electrode materials determine the thickness, morphology, and chemical composition of the SEI layer. Nature of the SEI on different systems determines important properties of the battery. We report on matrix assisted laser desorption time of flight mass spectrometry analysis (MALDI-TOF MS) of the SEI on model and practical anode materials. MALDI-MS analysis of anode materials showed that system specific long chain oligomers are formed during charge/discharge cycles. We will also present electrochemical surface stress measurements of anode materials using the bending cantilever method. Changes in mechanical properties of electrodes during SEI formation, and charge/discharge cycles have great practical consequences for the longevity of a Li-ion battery, since volume changes and stress variations can shorten the lifetime of the electrode materials. On Au surfaces when cycling between 2V to 0.3V (vs. Li/Li+), surface stress is compressive during cathodic scan. During the anodic scan, the compressive stress is removed, and surface stress returns to its original state. Further analysis of this region showed that an initial lithiation before full lithiation occurs at this potential range. First principles density functional theory (DFT) calculations for the Li on Au(111) overlayer models showed a compressive stress during the cathodic scan between 1.1 and 0.3 V. Bulk lithiation and Au-Li alloying happens at a lower potential, ca. 0.2 V. A residual tensile stress is observed on Au surfaces cycled to 0.15 V. This residual stress corresponds to the formation of oligomerized species in the SEI as shown in the MALDI analysis of Au surfaces emersed at different potentials.

Vacuum Insulation Panels with Tensile Supports to Increase the

Energy Efficiency of a Building’s Envelope

Alan D. Feinerman1,2, P. Gupta1, T. Dankovic2, and David W. Yarbrough3

1Thermal Conservation Technologies, 2University of Illinois at Chicago, 3R&D Services, Inc. Heating and cooling accounts for at least 36% of the energy consumed in the US and in nearly all cases increasing the insulation (R-value) of the thermal barrier will reduce the energy consumed. Space and economic considerations usually limit the insulation in the walls of a building’s envelope to R - 15 (ft2*hr*°F/Btu) which requires 3 to 4 inches of space. We are developing a ½ inch thick vacuum insulation panel (VIP) with tensile supports. This VIP will have an R value over 55 including edge losses on a 39 inch x 39 inch square panel. While the VIP can be used in the construction for new buildings, the real challenge is to develop economical methods to attach VIPs to existing buildings, since an exceedingly small fraction (< 1%) of buildings are constructed each year. Decreasing the energy consumption required for heating and cooling requires increasing the R value in existing building’s envelopes.


Kedar Manandhar1, Weronika Walkosz2, Michael Trenary1, and Peter Zapol2

1Department of Chemistry, University of Illinois at Chicago 2Materials Science Division, Argonne National Laboratory

The adsorption and reactions of NH3 and Ga(CH3)3 (TMG) on a single crystal surface of zirconium diboride, ZrB2(0001), were studied under ultrahigh vacuum conditions with the techniques of X-ray photoelectron spectroscopy (XPS) and reflection absorption infrared spectroscopy (RAIRS). These studies were motivated by the use of ammonia and TMG for growth of GaN by metal organic chemical vapor deposition (MOCVD), a popular commercial technique. Group III nitride semiconductors (AlN, GaN, InN, and their alloys) are important materials for applications in visible and ultraviolet optoelectronics, and high-power and high-frequency electronics. However, performance of the devices is limited by the large mismatch of lattice constants and thermal expansion coefficients between the nitride heteroepitaxial layers and the usually used substrates, sapphire, SiC and Si. Recently zirconium diboride (ZrB2), a refractory metallic compound, has been proposed as a promising substrate for GaN growth because of their similar lattice constants and thermal expansion properties. Moreover, ZrB2 being reflective and metallic, its use as a substrate in light emitting diodes (LEDs) minimizes loss of light and enables simplification of the device geometry as ZrB2 can be used as one of the ohmic contacts. Our results showed that at 95 K, both ammonia and TMG adsorbed molecularly on the ZrB2 surface. Upon annealing, ammonia and TMG started decomposing at ~ 140 K and ~215 K, respectively. Exposing at room temperature, NH3 completely dissociated to one nitrogen and three hydrogen atoms while TMG partially dissociated. Analysis of TMG dissociation pattern as a function of annealing temperature, quantitative analysis of uptake of nitrogen and gallium by the ZrB2(0001) surface, and of carbon incorporation in ZrB2 for room temperature exposure of the molecules will be presented and discussed. Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357.

Poster Presentations

1. Damon N. Hebert1, Angus A. Rockett Grain Boundaries and the Effect of Na on Emission of Cu-poor Cu(In,Ga)Se2 Thin Films

2. Zhu Liang1,Hyowon Kim2, Yousoo Kim2, and Michael Trenary1 Molecular structure of a mixed NH3–O2 overlayer on Pt(111)

3. Yuan Ren, Jun Yin, Michael Trenary Surface Chemistry of Vinyl Iodide on Pt(111)

4. Michael W. Majeski1, F. Douglas Pleticha1, Igor L. Bolotin1, Luke Hanley1, Eda Yilmaz2, Sefik Suzer2 Photoresponse of PbS nanoparticle – quarterthiophene films prepared by gaseous deposition as probed by XPS

5. Wan-Ting Chen1, Yuanhui Zhang1, Jixiang Zhang1

Assessment of Converting Wild Algae into Biocrude Oil via Hydrothermal Liquefaction: Product Distribution and Composition

6. Claire E. Tornow1, M.R. Thorson2, S. Ma2, A.A. Gewirth1, P.J.A. Kenis2 Nitrogen-based Ag Catalysts for the Electrochemical Reduction of CO2 to CO

7. Natalie A. Kautz1, Kevin D. Gibson1, Miki Nakayama1, Tuo Wang1, and Steven J. Sibener1 The Chemical and Structural Role of Oxides on Niobium Substrates For Use in Particle Accelerators

8. Tuo Wang1, Ying Zhao1, Sara Rupich1, Dmitri Talapin1 and Steven J. Sibener1 UHV STM and AFM Studies of Electronic Coupling between Quantum Dots

9. H. Hu1, J. M. Zuo1, L. Fang2, Y. Jia2, U. Welp2, G. W, Crabtree2 and W. K. Kwok2 Structure of Heavy-ion Irradiated High-Tc Superconductors

10. Kyle B. Ford1, Nassim E. Ajami1, Michael K. Collins1,2, Ghassan Al-Chaar1, Charles P. Marsh1,2 QD-Matrix Interaction in Nanocomposites: Implications for Device Efficiency

11. Yi Chen, Gang Logan Liu Lithography-less High-Throughput Manufacturing of Anechoic Silicon Nanocone Surface for Antireflective Solar Wafer Productions

12. Hadi Tavassol1, Maria Chan3, Maria Catarello1, Jeffrey Greeley3, David G. Cahill2, Andrew A. Gewirth1 Interfacial Processes in Li-ion Battery Anodes

13. Ryan D. Brown, James S. Becker, Zachary M. Hund, S.J. Sibener Determination of the Structure and Vibrational Dynamics of Methyl-Terminated Si(111) Using Helium Atom Scattering

Grain Boundaries and the Effect of Na on Emission of Cu-poor Cu(In,Ga)Se2 Thin Films

Damon N. Hebert1, Angus A. Rockett

1University of Illinois at Urbana-Champaign,

Department of Materials Science and Engineering

This study covers the role of grain boundaries (GBs) and the effect of Na on emission characteristics of Cu(In,Ga)Se2 thin films by use of the micro-scale probe techniques cathodoluminescence (CL) and electron backscatter diffraction (EBSD). Polycrystalline films deposited on Mo-coated soda lime glass are studied in planview and cross-section configurations. Information on grain orientation and GB misorientation allows for conclusions on their impact on emission.

Both inter- and intra-grain spectral contrast were observed. Luminescence is a result of recombination involving intrinsic defect states that are controlled by local crystal composition. Therefore, the observation of variation amongst the population of grains, even in good quality device material, indicates that there is poor compositional homogeneity amongst CIGS grains. But variation of emission characteristics within individual grains observed by CL indicates that composition variations are on a scale much smaller than individual grains. Nanometer scale compositions variations have been observed by micro-probe EDS by our group in the past but conclusions were in need of further verification, especially on samples that were not handled by TEM preparation methods. This inhomogeneity may be evidence of organization of defects and defect complexes.

Most GBs seem to be darkened in the CL but the trend is not consistent. Areas with a high density of closely-spaced GBs are especially darkened in the CL. Dark areas in CL indicate reduced radiative recombination, and thus indicate increased non-radiative recombination. The observation of decreased radiative recombination at GBs fits well with the theory that CIGS GBs repel majority carrier holes due to a potential barrier in the valence band. However, some GBs are observed that seem to have no effect on the emission. No trend was found for the effect of grain orientation, misorientation angle or GB-type on the emission behavior. However, a strong propensity for GBs to exhibit misorientations that correspond to specific twin boundary types in chalcopyrite thin films was identified. These twin boundaries are generally of high symmetry and low defect density. It is thought that twin boundaries are special cases of stacking faults and that they act as a mechanism to reduce strain during film growth and cooling. Propensity for twinning has been observed by other authors in sulfides and CuGaSe2 but work on chalcopyrite selenides has not been reported until now.

The effect of Na treatment was quite drastic. Since Na-containing and Na-free films were deposited simultaneously on different substrates, we were able to establish Na treatment as a cause of effects rather than a correlation with effects. The effect of Na treatment on the films was shown by the appearance of an additional deep emission in Na-free films. This is direct evidence that Na reduces point defect density and helps to improve crystalline quality during growth. The presence of Na led to larger grain sizes (~1.0 µm2), (112) texturing, grains aligned in the direction normal to the film surface, and the presence of both 60° and 71°- twin boundaries. In contrast, Na-free films showed small grain sizes (~0.14 µm2), a mixture of (220)/(204) and (112) texturing, randomly oriented grains, and the presence of mostly 60° twin boundaries. It is our opinion that most GBs in CIGS act as both collection areas for point defects and point defect clusters but also are more or less inactive with respect to recombination. This general model would predict that grain interiors are of higher material quality and that GBs are necessary and beneficial for high performance absorbers.

Molecular structure of a mixed NH3–O2 overlayer on Pt(111) Zhu Liang1, Hyowon Kim2, Yousoo Kim2, and Michael Trenary1

1Department of Chemistry, University of Illinois at Chicago, USA, 2Surface and Interface Science

Laboratory, RIKEN, Japan The interaction of NH3 with chemisorbed molecular O2 on a Pt(111) surface has been studied at the single-molecule level with low temperature scanning tunneling microscopy. Chemisorbed O2 molecules are found to form an ordered network at high coverages for adsorption temperatures below 50 K. Sites unoccupied by O2 molecules on Pt(111) appear as holes in the network. Various hole-hole distances among nearest neighbors are observed reflecting variations in the arrangement of O2 molecules. A hole-hole distance of 0.74 nm is found to be predominant on the surface and is assigned to be the most favorable one as it maintains the 3-fold symmetry of underlying platinum lattice. Ammonia molecules are observed to adsorb in the holes within the ordered network of O2 molecules, which is also the a-top site with respect to the Pt(111) substrate. Further annealing of the ammonia-oxygen overlayer to 400 K results in the formation of a mixed p(2×2) overlayer of N, O and NH. This work provides new insights into the ammonia oxydehydrogenation reaction on platinum surface, which is an important catalytic reaction in the industrial production of nitric acid.

Surface Chemistry of Vinyl Iodide on Pt(111)

Yuan Ren, Jun Yin, Michael Trenary

Department of Chemistry, University of Illinois at Chicago, 845 W Taylor Street, Chicago, IL 60607

Reflection absorption infrared spectroscopy and temperature programmed desorption were used to study the thermal decomposition of vinyl iodide (CHI=CH2) on Pt(111). Vinyl iodide molecules are found to dissociate into vinyl (HCCH2) species via C-I bond cleavage at temperature as low as 160 K, in agreement with a previous study using Auger electron spectroscopy and temperature programmed desorption. Vinyl is observed to hydrogenate to ethylene (CH2=CH2) between 190 and 230 K. Further annealing to 260 K causes ethylene to convert to ethylidene (CHCH3), which can be dehydrogenated to ethylidyne (CCH3) when annealed to temperatures higher than 300 K. With hydrogen coadsorption, cleavage of the C-I bond in vinyl iodide is enhanced and vinyl yields more ethylene than without hydrogen coadsorption. Conversion from ethylidene to ethylidyne seems to be promoted as no ethylidene is observed.

Photoresponse of PbS nanoparticle – quarterthiophene films prepared by gaseous deposition as probed by XPS

Michael W. Majeski1, F. Douglas Pleticha1, Igor L. Bolotin1, Luke Hanley1, Eda Yilmaz2, Sefik Suzer2

1Deparment of Chemistry, University of Illinois at Chicago, 4500 SES, 845 W. Taylor St., Chicago, Illinois,

60607-7061, USA, 2Department of Chemistry, Bilkent University, 06800 Ankara, Turkey Semiconducting lead sulfide (PbS) nanoparticles were cluster beam deposited into evaporated quaterthiophene (4T) organic films, which in some cases were additionally modified by simultaneous 50 eV acetylene ion bombardment. Surface chemistry of these nanocomposite films was first examined using standard X-ray photoelectron spectroscopy (XPS) and laser desorption postionization mass spectrometry. XPS was also used to probe photoinduced shifts in peak binding energies upon illumination with a CW green laser and the magnitudes of these peak shifts were interpreted as changes in relative photoconductivity. The four types of films examined all displayed photoconductivity: 4T only, 4T with acetylene ions, 4T with PbS nanoparticles, and 4T with both PbS nanoparticles and acetylene ions. Furthermore, the ion-modified films displayed higher photoconductivity, which was consistent with enhanced bonding within the 4T organic matrix and between 4T and PbS nanoparticles. PbS nanoparticles displayed higher photoconductivity than the 4T component, regardless of ion-modification. Finally, development of a new instrument is discussed that will allow analysis of films without prior exposure to air.

Assessment of Converting Wild Algae into Biocrude Oil via Hydrothermal Liquefaction: Product Distribution and Composition

Wan-Ting Chen1, Yuanhui Zhang1, Jixiang Zhang1

1University of Illinois at Urbana-Champaign

With the goal of incorporating bio-crude oil production along with waste water treatment, wild algae mixtures, consisting of different species of microalgae, macroalgae and bacteria, were cultured from waste water and this study assesses the feasibility of converting wild algae mixture into biocrude oil via hydrothermal liquefaction (HTL).The effects of reaction temperature and retention time on the product distribution and composition were explored. Hydrothermal liquefaction was conducted at temperatures from 260 ˚C to 320 ˚C for 30 to 90 minutes with 0.7 MPa N2 initial pressures. To improve the quality of the biocrude oil by decreasing the ash content within the feedstocks, 25%, 50% and 75% of swine manure were mixed with wild algae mixtures. The effects of the temperature, retention time and combination ratio of feedstocks are evaluated respectively. Distribution of biocrude oil, aqueous product, gaseous product and solid residue was collected and analyzed. The highest biocrude oil yield (on a dry matter basis) produced from wild algae mixtures was obtained at reaction temperature of 300 ˚C for 1.5 hour retention time. By combining 25% of swine manure with 75 % of algae mixtures on a dry matter basis, the biocrude oil yields could be improved by about 12 %. Elemental analysis demonstrated that carbon content of the biocrude oil first decreased as the temperature increased and then increased with further temperature increasing, which suggested that repolymerization reaction may occur when temperature increased from 260 ˚C to 320 ˚C. This phenomenon was consistent with the change trend of higher heating values (HHV). On the other hand, the carbon content increased as the retention time extended to 1 hour and then decreased when the retention time increased to 1.5 hour, which infers that endured reaction may lead to decomposition of the biocrude oil. Addition of the swine manure appears to be able to enhance the HHV of the biocrude. Summary of the elemental analysis is included in the Van Krevelen Diagram.

Fig. 1. Van Krevelen diagram of biocrude oil gained at different reaction conditions.

Nitrogen-based Ag Catalysts for the Electrochemical Reduction of CO2 to CO

Claire E. Tornow1, M.R. Thorson2, S. Ma2, A.A. Gewirth1, P.J.A. Kenis2

1University of Illinois Department of Chemistry, 2University of Illinois Department of Chemical &

Biomolecular Engineering The synthesis and application of carbon-supported nitrogen-based organometallic silver catalysts for the reduction of CO2 is studied using an electrochemical flow reactor. The performances of the N-based Ag catalysts towards the selective formation of CO are similar to those achieved when using Ag, the current state-of-the-art catalyst, but comparatively at much lower silver loadings. Faradaic efficiencies of the organometallic catalysts are higher than 90%, which again, are comparable to those of Ag. Furthermore, with the addition of an amine ligand to Ag/C, the partial current density for CO increases significantly, suggesting the presence of a possible co-catalyst mechanism. Additional improvements in activity and selectivity are expected as greater insight is obtained on the mechanism of CO2 reduction at these catalysts.

The Chemical and Structural Role of Oxides on Niobium Substrates For Use in Particle Accelerators

Natalie A. Kautz1, Kevin D. Gibson1, Miki Nakayama1, Tuo Wang1, and

Steven J. Sibener1

1The James Franck Institute and Department of Chemistry, The University of Chicago, Gordon Center for Integrative Science, 929 E. 57th Street, Chicago, IL 60637

Niobium is a superconducting metal used for Superconducting Radio Frequency (SRF)-cavities in particle accelerators. Chemical and structural defects in the niobium can significantly reduce cavity performance and, in some instances, render them useless especially when placed under high field gradients. We probe the chemistry, defect structure and oxidative states of niobium poly- and single-crystal substrates using a number of surface science techniques. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) show significant changes in the coverage and chemical state of niobium oxides resulting from a number of sputtering and low-temperature thermal annealing treatments. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) reveal that despite extensive chemical polishing on a polycrystalline cavity substrate, a large number of surface defects and weld pits still exist on the surface. Changes in local surface structure are investigated more thoroughly using scanning tunneling microscopy (STM), a unique tool that allows us to investigate how changes in local surface structure (step edges, dislocation, point defects, grain boundaries) impact the oxidation of niobium substrates. We use single crystal niobium samples to study how crystalline structure, terrace shape and size, step edges, and surface dislocations influence the absorption, dissolution, and formation of surface oxides. The motivation for these studies comes in part from the observation that baking at relatively modest processing temperatures between 100-400 °C can lead to notable improvement in the accelerating field of extant cavities without quality factor degradation. High-temperature heating minimizes the presence of surface oxides and very different oxide structures are formed on the (111) and (100) single-crystal surfaces when sub-surface oxygen re-emerges upon cooling to room temperature. The orientation of the initially chosen single crystal surface significantly influences surface oxide formation; we observe that the (111) face does not form long-range ordered oxides, while the (100) surface presents highly-organized (nx1) ladder structures. We will discuss the stability and interconversion of the (nx1) oxides arising from thermal cycling with or without the addition of gas-phase oxygen, with particular focus on oxygen dissolution induced by relatively low-temperature annealing of the substrate.

UHV STM and AFM Studies of Electronic Coupling between Quantum Dots

Tuo Wang1, Ying Zhao1, Sara Rupich1, Dmitri Talapin1 and Steven J. Sibener1

1The James Franck Institute and Department of Chemistry, The University of Chicago, Gordon Center for Integrative Science, 929 East 57th Street, Chicago, IL 60637 USA

Quantum dots are semiconductor nanostructures typically consisting of thousands of atoms. Quantum dots are also known as artificial atoms because of their discrete atom-like energy levels, which result from the three dimensional quantum confinement of electrons. However, in quantum dot clusters such as dimers, trimers, or larger ensembles the electronic properties of such nanoparticles can also be affected by proximity to neighboring dots due to quantum coupling. In this study, quantum coupling effects between quantum dots are being investigated using scanning tunneling (STM) and conductive atomic force (AFM) microscopy. The electronic local density of states (LDOS) of the quantum dots are measured by tunneling spectroscopy at different temperatures of different quantum dot systems – arrays, single dots, and oligomers. Quantum coupling effects are explored as indicated by changes in the observed spectra. Upon further analysis, it is shown how quantum coupling between dots causes changes in the zero-conductance gap, energy peak shifts and spectral feature widening. By probing electronic properties of quantum dot oligomers having different material composition, size, shape, and spatial separation, this study will eventually give us a better understanding of the physical mechanisms of quantum coupling and provide effective ways to tune coupling in QD arrays.

Structure of Heavy-ion Irradiated High-Tc Superconductors

H. Hu1, J. M. Zuo1, L. Fang2, Y. Jia2, U. Welp2, G. W, Crabtree2 and W. K. Kwok2

1University of Illinois at Urbana-Champaign, Urbana, IL, 61801

2Argonne National Laboratory, Argonne, IL, 60439 Discovery of high-Tc superconductors has attracted great interest since 1987 not only for the fundamental study of superconductivity, but also for their applications, especially in efficient power transmission. Critical current density Jc, which is the maximum electric current density that the superconductors can carry without resistance, is an important property in the applications involving power cables, electric motors and generators, etc. Enhancement of Jc and its directional isotropy can be achieved by introducing flux pinning defects, such as grain boundaries, precipitates and irradiation tracks. Correlating the structure with flux pinning performance is required for further improvement of these materials. In this presentation, the effects of Pb-ion irradiation on Jc of newly-discovered Ba0.6K0.4Fe2As2 and YBa2Cu3O6+x(YBCO) superconductors are studied by scanning transmission electron microscopy(STEM). The pristine Ba0.6K0.4Fe2As2 single crystals were irradiated by 1.4GeV Pb-ions along c-axis at different dose-matching fields of BΦ = 4, 6, 10, 21 and 50T, respectively. The transition temperature (37.5K) and width show little change for doses up to 21T in the measurement of magnetization in a field of 10G along c-axis. Compared to the pristine sample, Jc increases strongly by several times at 5K and is field independent up to 5T in the sample irradiated under BΦ = 21T (corresponding to density of damage tracks ~ 1012 ions/cm2). The planar-view STEM images along c-axis reveal that the damage tracks have average diameter ~3.7nm. With such a small size of columnar defects, the degradation of superconducting materials is minimized, leading to the unprecedented concentration of strong pinning tracks. The cross-sectional STEM images along a-axis show that the damage tracks are discontinuous. Cuprate YBCO superconductors are used prototype commercial power cables. A major materials challenging is the improvement of isotropy of Jc for better power transmission performance. The pristine commercial tape has larger Jc in a-b plane than that along c-axis due to its layered structure, resulting in an isotropy factor of Ja-b/Jc ~ 2. To improve the isotropy of Jc, the tape was irradiated by 1.4GeV Pb-ions along both +/-45° direction respect to c-axis at different dose-matching fields of BΦ = 1,2 and 4T, which leads to an isotropy factor as small as 1.3. The cross-sectional STEM images along a-axis show that the damage tracks are about 10nm in diameter and they are continuous. Our results present the effect of heavy-ion irradiation on enhancement of Jc, and with optimal irradiation angles, the isotropy of Jc can also be improved. STEM technique is shown to be a powerful tool to study microstructure of damage tracks in superconductors.

QD-Matrix Interaction in Nanocomposites: Implications for Device Efficiency

Kyle B. Ford1, Nassim E. Ajami1, Michael K. Collins1,2, Ghassan Al-Chaar1, Charles P. Marsh1,2

1CERL-ERDC, 2Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois

Quantum dots (QDs) have been applied in a variety of situations, from biological systems to solar cells and each system brings with it a series of challenges for QD application. Especially relevant to maximizing efficiency for QD applications in displays and photovoltaics, we report here our work examining the interaction between QD and matrix in nanocomposite materials. We have experimentally explored the effects of strain applied to an epoxy-QD nanocomposite on the fluorescence of the embedded quantum dots. These fluorescence measurements can provide suggestions for optimization regarding energy flow and device efficiency for devices utilizing embedded QDs. Our results suggest that the QD-matrix interaction may be dominated by an electronic effect, even for shelled QDs.

Lithography-less High-Throughput Manufacturing of Anechoic Silicon Nanocone Surface for Antireflective Solar Wafer Productions

Yi Chen, Gang Logan Liu

Micro and Nanotechnology Laboratory, Department of Electrical and Computer Engineering, University of

Illinois at Urbana-Champaign, Urbana, IL, United States To improve light absorption, previously various antireflection material layers were created on solar wafer surface including multilayer dielectric film, nanoparticle sludges, microtextures, noble metal plasmonic nanoparticles and 3D silicon nanostructure arrays. In comparison our nanomanufacturing, a unique unique synchronized and simultaneous top-down and bottom-up nanofabrication approach called simultaneous plasma enhanced reactive ion synthesis and etching (SPERISE), offers a better antireflection solution along with the potential to increase p-n junction surface area. High density and high aspect ratio anechoic nanocone arrays are repeatedly and reliably created on the entire surface of single and poly crystalline silicon wafers as well as amorphous silicon thin films within 5 minutes under room temperature. The demonstrated manufacturing process can be readily translated into current industrial silicon solar cell fabrication lines to replace the costly and ineffective antireflective coatings.


Hadi Tavassol1, Maria Chan3, Maria Catarello1, Jeffrey Greeley3, David G. Cahill2, Andrew A. Gewirth1

1Department of Chemistry, 2Department of Materials Science and Engineering, University of Illinois, 3Argonne National Laboratory

During Li+ transport, in Li-ion batteries, a solid electrolyte inter-phase (SEI) composed of breakdown products from the electrode, the solvent, and the electrolyte, forms on both cathode and anode electrode surfaces. Solvents, electrolytes, and electrode materials determine the thickness, morphology, and chemical composition of the SEI layer. Nature of the SEI on different systems determines important properties of the battery. We report on matrix assisted laser desorption time of flight mass spectrometry analysis (MALDI-TOF MS) of the SEI on model and practical anode materials. MALDI-MS analysis of anode materials showed that system specific long chain oligomers are formed during charge/discharge cycles. We will also present electrochemical surface stress measurements of anode materials using the bending cantilever method. Changes in mechanical properties of electrodes during SEI formation, and charge/discharge cycles have great practical consequences for the longevity of a Li-ion battery, since volume changes and stress variations can shorten the lifetime of the electrode materials. On Au surfaces when cycling between 2V to 0.3V (vs. Li/Li+), surface stress is compressive during cathodic scan. During the anodic scan, the compressive stress is removed, and surface stress returns to its original state. Further analysis of this region showed that an initial lithiation before full lithiation occurs at this potential range. First principles density functional theory (DFT) calculations for the Li on Au(111) overlayer models showed a compressive stress during the cathodic scan between 1.1 and 0.3 V. Bulk lithiation and Au-Li alloying happens at a lower potential, ca. 0.2 V. A residual tensile stress is observed on Au surfaces cycled to 0.15 V. This residual stress corresponds to the formation of oligomerized species in the SEI as shown in the MALDI analysis of Au surfaces emersed at different potentials.

Determination of the Structure and Vibrational Dynamics of Methyl-Terminated Si(111) Using Helium Atom Scattering

Ryan D. Brown, James S. Becker, Zachary M. Hund, S.J. Sibener

The Department of Chemistry and the James Franck Institute, The University of Chicago

Helium atom scattering from methyl-terminated silicon gives insight into adlayer organization and the interplay of molecular and lattice vibrations for this complex organic-semiconductor surface. Helium atom diffraction indicates the presence of large (1x1) methyl-terminated Si(111) terraces with low defect density. Debye-Waller attenuation measurements were used to characterize the average thermal motion of this interface. Single-phonon inelastic scattering easily observes the Rayleigh wave dispersion of this complex surface. Calculations and experiment agree that this surface wave hybridizes with a libration of the terminal methyl group.

avs materials for energy · 2019-06-26 · ccr avs materials for energy september 6, 2012 meeting...

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