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February 2015
Sunday Monday Tuesday Wednesday Thursday Friday Saturday

1

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2

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6

  1. CFN Proposal Deadline

    11:45 pm, CFN

7

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8

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17

  1. CFN Workshop

    9:30 am, CFN Second Floor Seminar Room

    Hosted by: Aaron Stein

    Second CFN Workshop on Electron Beam Lithography Tuesday and Wednesday February 17 & 18, 2015 9:30am - 4:30pm Electron beam lithography (EBL) is a key enabling tool for nanofabrication and nanoscience. The Nanofabrication facility at the Center for Functional Nanomaterials (CFN) at Brookhaven National Laboratory (BNL) invites its Users, potential CFN Users, external EBL users both novice and expert and anyone else interested in learning about this technique to a workshop to on electron beam lithography. The Workshop will include presentations on electron beam lithography techniques and results from current users. Also highlighted will be tips and strategies from CFN Personnel on how to effectively use our Nanofabrication facilities. The workshop will focus on practical information about specific techniques, applications and troubleshooting. Short talks will take place in an informal setting with plenty of time for questions and discussion. This is an excellent opportunity to learn about the different types of structures and applications of EBL, to get answers to questions both basic and complex and to help build your EBL knowledge base. One full day of the workshop will be devoted to pattern preparation techniques. Featured will be an applications engineer from GenISys Inc. to present the BEAMER software with hands-on demonstrations of advanced pattern conversion techniques and tutorials on the use of proximity effect correction.

18

  1. CFN Workshop

    9:30 am, CFN Second Floor Seminar Room

    Hosted by: Aaron Stein

    Second CFN Workshop on Electron Beam Lithography Tuesday and Wednesday February 17-18, 2015 9:30am - 4:30pm Electron beam lithography (EBL) is a key enabling tool for nanofabrication and nanoscience. The Nanofabrication facility at the Center for Functional Nanomaterials (CFN) at Brookhaven National Laboratory (BNL) invites its Users, potential CFN Users, external EBL users both novice and expert and anyone else interested in learning about this technique to a workshop to on electron beam lithography. The Workshop will include presentations on electron beam lithography techniques and results from current users. Also highlighted will be tips and strategies from CFN Personnel on how to effectively use our Nanofabrication facilities. The workshop will focus on practical information about specific techniques, applications and troubleshooting. Short talks will take place in an informal setting with plenty of time for questions and discussion. This is an excellent opportunity to learn about the different types of structures and applications of EBL, to get answers to questions both basic and complex and to help build your EBL knowledge base. One full day of the workshop will be devoted to pattern preparation techniques. Featured will be an applications engineer from GenISys Inc. to present the BEAMER software with hands-on demonstrations of advanced pattern conversion techniques and tutorials on the use of proximity effect correction.

19

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21

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22

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23

  1. Center for Functional Nanomaterials Seminar

    10 am, CFN, Building 735, 1st floor, conference room B

    Hosted by: Chuck Black

    Center for Functional Nanomaterials Seminar Monday, February 23, 2015 10:00 a.m. Conference Room B Capillary instability of periodic polymer thin-film structures Zheng Zhang Department of Mechanical Engineering University of Colorado at Boulder In this talk, I will present the simultaneous capillary instability among periodic polymer lithographic structures. The first system is straight polymer stripes arranged in parallel with equal spacing and suspended atop an immiscible medium. Polystyrene (PS) and poly (methyl methacrylate) (PMMA) were used because of their immiscibility and well-characterized physical properties. When annealed at a temperature above the glass transition temperature of both component polymers, the stripes undulated and ruptured via capillary instability. We found that the PS-to-PMMA viscosity ratio and substrate confinement to be key factors that influenced the instability. The second system that I will show is suspended concentric PS rings. The rings ruptured upon annealing, with three possible types of phase correlation between neighboring rings. In the case of weak substrate confinement, the rings ruptured independently when they were sparsely distanced, but via an out-of-phase mode when packed closer. If the substrate confinement was strong, the rings would rupture via an in-phase mode, resulting in radially aligned droplets. The concentric ring geometry caused a competition between the phase correlation of neighboring rings and the kinetically favorable wavelength, yielding an intriguing, recursive surface pattern. This frustrated pattern formation behavior was accounted for by a scaling analysis. Our experiments can serve as a basis for correlated capillary instability among curved objects, which can be a powerful tool for creating unique surface patterns. Host: Charles

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26

  1. Center for Functional Nanomaterials Seminar

    1 pm, CFN, Building 735, Conference Room B

    Hosted by: Qin Wu

    In this talk, I will show that a subsystem formulation of DFT can simplify both the theoretical framework and the computational effort for calculating the electronic structure of condensed phase systems. I claim that the naturally subsystem-like form of molecular aggregates (including molecules at surfaces) makes subsystem DFT a better descriptor of the underlying physics than regular DFT of the supersystem. This claim will be sustained by two examples. The first one is a novel van der Waals DFT theory based on the subsystem DFT approach which addresses several drawbacks of common vdW functionals as well as SAPT-type formulations " it is theoretically exact and amenable to sensible approximations. The second example involves the analysis of the electronic spectra of molecular chromophores embedded in a molecular environment. It uncovers interactions between the chromophore and its environment which we term "holographic spectrum". Computational evidence to the claims will be provided, and it is obtained from a local version of the Amsterdam Density Functional software and a brand new implementation of subsystem DFT (both ground and excited states) in the plane wave code Quantum-Espresso. I will discuss several pilot calculations which include molecules at surfaces and layered systems. Recent references from the Pavanello group: [1] On the subsystem formulation of linear-response time-dependent DFT, J. Chem. Phys. 138 , 204118 (2013) [2] Subsystem real-time Time Dependent Density Functional Theory, J. Chem. Phys. submitted, arXiv:1502.01324 [3] Periodic subsystem density-functional theory, J. Chem. Phys. 141 , 174101 (2014) [4] FDE-vdW: A van der Waals inclusive subsystem density-functional theory, J. Chem. Phys. 141 , 044127 (2014) [5] Quantifying Environmental Effects on the Decay of Hole Transfer Couplings in Biosystems, J. Chem. Theory Comput., 2014, 10 (6), pp 2546��"2556

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  1. MAR

    10

    Tuesday

    Center for Functional Nanomaterials Colloquium

    "The bulk photovoltaic effect in polar oxides for robust and efficient solar energy harvesting"

    Presented by Andrew M. Rappe, University of Pennsylvania

    11 am, Bldg 735, Seminar Room 2nd Floor

    Tuesday, March 10, 2015, 11:00 am

    Hosted by: Deyu Lu

    Solar energy is the most promising source of renewable, clean energy to replace the current reliance on fossil fuels. Ferroelectric (FE) materials have recently attracted increased attention as a candidate class of materials for use in photovoltaic devices. Their strong inversion symmetry breaking due to spontaneous polarization allows for excited carrier separation by the bulk of the material and voltages higher than the band gap (Eg), which may allow efficiencies beyond the Shockley-Queisser limit. Ferroelectric oxides are also robust and can be fabricated using low cost methods such as sol-gel thin film deposition and sputtering. Recent work has shown how a decrease in ferroelectric layer thickness and judicious engineering of domain structures and FE-electrode interfaces can dramatically increase the current harvested from FE absorber materials. Further improvements have been blocked by the wide band gaps (Eg =2.7-4 eV) of FE oxides, which allow the use of only 8-20% of the solar spectrum and drastically reduce the upper limit of photovoltaic efficiency. In this talk, I will discuss new insight into the bulk photovoltaic effect, and materials design to enhance the photovoltaic efficiency. We calculate from first principles the current arising from the "shift current" mechanism, and demonstrate that it quantitatively explains the observed current. Then, we analyze the electronic features that lead to strong photovoltaic effects. Finally, we present new oxides that are strongly polar yet have band gaps in the visible range, offering prospects for greatly enhanced bulk photovoltaic effects. Please note: If anyone would like to schedule a meeting with Dr. Rappe, please contact Deyu Lu (dlu@bnl.gov)

  2. MAY

    31

    Sunday

    CFN Proposal Deadline

    "CFN Proposal Deadline for September-December Cycle 2015"

    11:45 pm, CFN

    Sunday, May 31, 2015, 11:45 pm

  3. SEP

    30

    Wednesday

    CFN Proposal Deadline

    "CFN Proposal Deadline for January-April Cycle 2016"

    11:45 pm, CFN

    Wednesday, September 30, 2015, 11:45 pm