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  • Confined Deposition
    Badding Group Fall 2011

    In the garden of the new Millenium Science Complex.

  • Confined Deposition
    High Pressure Chemistry for Electronic Devices

    Layering of high speed Pt-Si photodiodes into extreme aspect ratio pores: Nature Photonics, DOI:10.1038/NPHOTON.2011.352

  • Confined Deposition
    Confined Chemical Deposition

    Templated growth of amorphous hydrogenated silicon: J.Am.Chem.Soc. v.134, p.19 (2012)

  • Confined Deposition
  • Confined Deposition
    Silane Unimolecular Rate Constant vs Pressure

    Acceleration of reaction rate allows for plasma-free, 100% efficient deposition of a-Si:H, an important solar cell material.

  • ZnSe Wire
    Optical Fiber Nano/microtemplates Drawn at University of Southampton

    Long, ordered, strong, designable, scalable, and transparent platform for organizing molecules and materials down to nanoscale dimensions

  • ZnSe Wire
    Atomically Smooth Zinc Selenide Wires

    Uniform crystal field environment for transition metal doping that enables light emission:Adv. Mater. v.23, p.1647 (2011)

  • Confined Deposition
    Transparent Phase of Carbon

    Low activation barrier transition between transparent phase and graphite: Phase Transitions v.80, p.1033 (2007)

  • Confined Deposition
    Jet Blown Teflon Nanofibers

    Nanofibers of non melt processable PTFE for enhanced cell adhesion: Polymer v.47 p.8337 (2006)

  • Confined Deposition
    Silicon Single Crystals Grown in Extreme Aspect Ratio Pores

    Fluid Liquid Solid Growth: Advanced Materials v.20 p.1135 (2008)

  • Confined Deposition
    With University of Southampton Collaborators

    In front of the Gateway to the Sciences

  • Confined Deposition
    Germanium Nanowire "Brush"

    Science v.311 p.1583 (2006)

  • Confined Deposition
    Silicon Web

    Conformal deposition in honeycomb template

  • Confined Deposition
    Size Tuned Bismuth Telluride Nanoparticles

    Thermoelectric properties: Small v.5 p.933 (2009)

  • Confined Deposition
    Patterned Self-Assembled Monolayers in Silica Capillaries

    Langumuir v.24 p.3636 (2006)

  • Confined Deposition
    Raman of Molecular Monolayers in Silica Pores

    Langmuir v.27 p.630 (2011)

  • Confined Deposition
    Void-free filling of Extreme Aspect Ratio Templates

    Centimeters long silicon nanowires and nanopores: Adv. Mater. v.22, p.4605 (2010)


Research Overview

General Theme

A unifying theme in the Badding group's research is the use of pressure to synthesize or probe solid state materials. We are interested in materials that have unusual structure or chemical/physical behavior and often apply them to problems of significant technological interest. Photonic materials, energy materials for photovoltaics and hydrogen storage, and high strength materials have recently been of particular interest.

Pressure is a thermodynamic variable that is as fundamental as temperature, but is relatively underutilized in materials chemistry research.

Pressure is a thermodynamic variable that is as fundamental as temperature, but is relatively underutilized in materials chemistry research. It can, for example, control interatomic distance (without much variation in other quantities such as the entropy) (1), tune reaction chemical kinetics and thermodynamics (often over a much wider range than is possible with temperature) (1), allow for solvents with hybrid liquid-like and gas-like properties, and infiltrate molecules and materials into near atomic scale voids. Superior materials properties or interesting behavior not possible without the use of pressure for chemical synthesis or tuning can thus be obtained. At the micro and nano scales, the use of high pressures becomes much easier because pressure is force per unit area and the forces involved become very small as the area decreases. We use a wide range of pressure from just above atmospheric (0.1 megapascals) to tens of gigapascals.


News 2012

  • Brief Summary of Past Research

    "New" Elements

    We have shown that "new" elements (2) such as potassium, although alkali elements at ambient pressure, can react chemically like a transition element with a single electron in a d-orbital upon compression to gigapascal pressures. Unusual graphite-like sheets (see AgK2 figure) of potassium atoms (red) intercalated with silver atoms (black) in AgK2 can form, for example (3).

    Carbon Materials

    We have also investigated carbon materials such as the sp3-bonded "transparent phase", a new form of carbon (4) that forms upon compression of (sp2-bonded) graphite (5), networks formed from benzene molecules (6), diamond formed directly from C60 at ambient temperature (7), and carbon nitrides (8). Multiwavelength Raman spectroscopy (9) with excitation wavelengths from the deep UV to the near IR has proved to be a powerful tool for characterizing these materials. The insights from these curiosity driven studies of carbons reversible rehybridization behavior may help in the search for improved hydrogen storage materials, new phases of carbon and high strength carbon materials.

    Materials Discovery by Pressure Tuning

    We have used pressure for a "combinatorial" approach to complex materials discovery because fundamental parameters such as orbital overlap can be tuned very precisely and over a wide range (1). For example, our pressure tuning experiments have shown that the figure of merit of the most technologically important thermoelectric material, antimony bismuth telluride, can be doubled to two (10).

  • Current Research

    Confined Chemical Deposition in Extreme Aspect Ratio Nanotemplates for Photonics and More
    We use chemistry to develop new ways to organize inorganic semiconductor, metallic, and molecular materials in 1-d templates at dimensions down to the nanoscale.

    The controlled hierarchical assembly of individual nanoscale elements such as quantum dots and nanowires into high-quality, precisely designed functional materials and devices provides a compelling challenge in nanoscience. We use chemistry to develop new ways to organize inorganic semiconductor, metallic, and molecular materials in 1-d templates at dimensions down to the nanoscale. The resulting 1-d structures are natural conduits for light, electrons, and flowing gases or fluids, which can be manipulated and coupled together inside them in many useful ways over centimeters to meters long length scales.

    Silica microstructured optical fiber nanotemplates can have arrays of pores designed in virtually any desired pattern (see MOF figure). These meters long pores can have diameters from microns to nanometers in one template and can be precisely spatially arranged relative to each within nanometers. Our research has demonstrated that by treating these ultra-high aspect ratio pores as high pressure chemical reactors we can fill them void free (11) with unary (12) and compound semiconductors (13) (see cross-sectional SEM figure). The resulting near atomically smooth (14) nano or microscale diameter semiconductor wires and tubes are much longer and more geometrically perfect than structures typically made by conventional nanofabrication methods. They have the further advantage that they are embedded in a macroscale size, rugged, functional template that makes them easy to handle and allows light, electricity and/or flowing fluids to be readily coupled into them. Major research focuses are developing high pressure chemistry to make atomically smooth, geometrically perfect structures with high materials quality that have excellent optical and electronic properties and organizing these structures with increasing sophistication in templates.

    Layer by layer deposition in the pores can also form very uniform doped semiconductor homo and heterojunctions (see junction figures) (15). The "outside-in" nature of this template-based approach to annular junctions contrasts with the usual approach of depositing on the exterior of nanowires. Patterning a junction adjacent to a central silica core allows for a unique light coupling scheme that overcomes the difficulties in transferring light from low refractive index silica to high index silicon without a large impedance mismatch (15).

    The extreme aspect ratios, spatial organization, and geometric perfection of these wires and junctions make them of interest for a wide range of applications

    The extreme aspect ratios, spatial organization, and geometric perfection of these wires and junctions make them of interest for a wide range of applications, including high speed optoelectronic fiber devices (15), nanofluidics, all optical signal processing, chemical sensors (16), optical waveguides (17), high quality factor resonators (18), subwavelength high resolution infrared imaging (19), non-linear optics (20), solar cells, confined 1-d physics, and fiber lasers. To pursue these applications, group members often work with our collaborators, including the Southampton University ORC in the UK, and the Gopalan group at Penn State. Templated high pressure deposition is practical and scalable in view of the small volumes of reactants employed. See the in the news for some outside perspectives on applications.

    In addition to inorganic solids, self-assembled molecules (16, 21) can be layered, patterned, and characterized via Raman spectroscopy within the arrays of pores in fiber nanotemplates to provide further flexibility in hierarchically organizing complex materials.

    Nearly every aspect of the pathway from molecular precursor to reaction product, including reactant flow, surface chemistry, chemical kinetics and thermodynamics, and nucleation and growth, differs from that under conventional conditions.

    The behavior of molecules compressed to high pressures and constrained to the small dimensions of the nano/microreactors is dramatically altered. Nearly every aspect of the pathway from molecular precursor to reaction product, including reactant flow, surface chemistry, chemical kinetics and thermodynamics, and nucleation and growth, differs from that under conventional conditions (11). There are kinetic/flow effects that increase reactant concentration (22). Supersonic flow can form nanonozzles (22). The width of the "stagnant" layer of precursor present near the reaction interface at low reaction pressures in large volume reactors is greatly reduced. Competition between single crystal growth and deposition on pore walls must be controlled (23). The nm long mean free paths and associated high molecular collision frequency in silane precursor allows for reaction at low enough temperatures for templated growth of nanowires of hydrogenated amorphous silicon (11), a material that is useful for non-linear optics and solar cells. Dopant molecule reaction kinetics and thermodynamics has to be understood to allow for carefully regulated impurity doping and formation of junctions with a built-in potential (15). We have also shown that the remarkable transport properties of pressure driven precursors allows for the formation of nanopores in semiconductor wires many centimeters long (13). We use a combination of experiment and theory/modeling to determine how chemistry is altered under the unusual reaction conditions employed (11, 12, 22, 23). Exploiting these differences to make materials and structures is central to our research.

    Rehybridization in Carbon Materials

    Unsaturated carbon molecules and materials can rehybridize to sp3-bonded carbon upon compression (4). Hydrogen can affect this rehybridization by bonding to compressed carbon. We are continuing to investigate these rehybridization effects in carbon in collaboration with Angela Lueking and Vin Crespi at Penn State and the Carnegie Institution of Washington. Applications of interest include hydrogen storage materials and high strength materials.

    Nanofibers of Non-Melt Processible Polymers

    We discovered that pressure driven flow can be used to make nanofibers of polytetrafluoroethylene (Teflon) (24) that cannot be made by other means because of the non-melt processible nature of this polymer. Adhesion of proteins and cells (25) to these materials is now under investigation.




AgK2: Graphite-like potassium (red) intercalated with silver (black).
AgK2 graphite-like potassium (3) formed by high pressure reaction between potassium and silver.

MOF templates fabricated at the University of Southampton
Silica microstructured optical fiber templates drawn at the ORC.

Patterned Deposition in Silica Template
Cross-sectional SEM of precise spatial organization of silicon tubes in a silica MOF template. The pores in these silica templates can be as small as 10 nm and meters long.

High Pressure Chemistry for Electronic Devices
Schematic of an annular Pt-Si Schottky junction constructed in a pore using high pressure chemistry. Light (red arrows) is guided in the undoped i-Si layer. This device detects light with 3 GHz bandwidth (15).

High Pressure Chemistry for Electronic Devices
Cross sectional image of a centimeters long annular doped Pt-Si Schottky junction constructed in a pore using high pressure chemistry (15). The bottom panel shows the Raman spectroscopic q parameter, which reveals changes in doping, across the junction.

Funding

  • Confined Deposition
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  • Confined Deposition


We thank the National Science Foundation (NSF DMR-0502906, DMR-0806860, DMR-1107894), the Department of Energy (DOE), the Carnegie Institution of Washington EFREE DOE Energy Frontier Research Center, the Air Force, the Center for Optical Technologies (COT), and the Penn State MRSEC, funded by the National Science Foundation, for support.



Selected Publications

  • (1) Badding, J. V. High-pressure synthesis, characterization, and tuning of solid-state materials. Annual Review of Materials Science 28, 631 (1998).
  • (2) Parker, L. J., Atou, T. & Badding, J. V. Transition element-like chemistry for potassium under pressure. Science 273, 95 (1996).
  • (3) Atou, T., Hasegawa, M., Parker, L. J. & Badding, J. V. Unusual Chemical Behavior for Potassium under Pressure: Potassium-Silver Compounds. Journal of the American Chemical Society 118, 12104 (1996).
  • (4) Badding, J.V., Lueking, A.L., Reversible High Pressure sp2-sp3 Transformations in Carbon, Phase Transitions, 80, 1033 (2007)
  • (5) Miller, E. D., Nesting, D. C. & Badding, J. V. Quenchable Transparent Phase of Carbon. Chemistry of Materials 9, 18 (1997).
  • (6) Jackson, B. R., Trout, C. C. & Badding, J. V. UV Raman Analysis of the C:H Network Formed by Compression of Benzene. Chemistry of Materials 15, 1820 (2003).
  • (7) Ravindran, T. R. & Badding, J. V. Ultraviolet Raman analysis of the formation of diamond from C60. Solid State Communications 121, 391 (2002).
  • (8) Badding, J. V. Solid-state carbon nitrides. Advanced Materials 9, 877 (1997).
  • (9) Ravindran, T. R., Jackson, B. R. & Badding, J. V. UV Raman Spectroscopy of Single-Walled Carbon Nanotubes. Chemistry of Materials 13, 4187 (2001).
  • (10) Polvani, D. A., Meng, J. F., Shekar, N. V. C., Sharp, J. & Badding, J. V. Large Improvement in Thermoelectric Properties in Pressure-Tuned p-Type Sb1.5Bi0.5Te3. Chemistry of Materials 13, 2068 (2001).
  • (11) Baril, N.F, He, R., Day, T.D., Sparks, J.R., Keshavarzi, B, , Krishnamurthi, M, Borhan, A, Gopalan, V, Peacock, A.C, Heal, N, . Sazio, P.J.A., and Badding, J. V. Confined High-Pressure Chemical Deposition of Hydrogenated Amorphous Silicon, Journal of the American Chemical Society, 134, 19-22 (2012).
  • (12) Sazio, P. J. A., Amezcua-Correa, A., Finlayson, C. E., Hayes, J. R., Scheidemantel, T. J., Baril, N. F., Jackson, B. R., Won, D.-J., Zhang, F., Margine, E. R., Gopalan, V., Crespi, V. H. & Badding, J. V. Microstructured Optical Fibers as High-Pressure Microfluidic Reactors. Science 311, 1583 (2006).
  • (13) Sparks, J.R., He, R., Healy, N., Krishnamurthi, M, Peacock, A.M., Sazio, P.J.A., Gopalan, V. Badding, J.V. Zinc Selenide Optical Fibers, Advanced Materials, 23, 1647 (2011).
  • (14) Healy, N., Lagonigro, L., Sparks, J.R., Boden, S., Sazio, P.J.A., Badding, J.V., and Peacock, A.C., Polycrystalline silicon optical fibers with atomically smooth surfaces, Optics Letters, 36, 12480-2482 (2011).
  • (15) He, R.,Sazio, P.J.A., Peacock, A.C, Heal, N., Sparks, J.R., Krishnamurthi, M, Gopalan, V, and Badding, J. V., Integration of GHz Bandwidth Semiconductor Devices inside Microstructured Optical Fibres, Nature Photonics, 6, 174-179 (2012).
  • (16) Calkins, J.A., Peacock, A.C, Sazio, P. J. A., Allara, D.L., and Badding, J. V. Spontaneous Waveguide Raman Spectroscopy of Self-Assembled Monolayers in Silica Micropores, Langmuir, 27, 630 (2011).
  • (17) Mehta, P., Krishanmurthi, M., Healy, N., Baril, N. F., Sparks, J., Sazio, P. J. A., Gopalan,V., Badding, J. V. and Peacock, A. C. Mid-infrared transmission properties of amorphous germanium optical fibers, Applied Physics Letters, 97, 071117 (2010).
  • (18) Vukovic, N, Healy, N, Horak, P., Sparks, J.R., Sazio, P.J.A., Badding, J.V., and, Peacock, A.C., Ultra-smooth microcylindrical resonators fabricated from silicon optical fibers, Applied Physics Letters, 99. 03117 (2011).
  • (19) Krishnamurthi, M, Sparks, J.R., He, R.,Temkyh, I., Baril, N.F., Liu, Z., Sazio, P.J.A., Badding, J. V., and Gopalan, V, An Array of Tapered Semiconductor Waveguides in a Fiber for Infrared Image Transfer and Magnification Optics Express, 20, 4168-4175 (2012).
  • (20) Mehta, P., Healy, N., Baril,N. F., Sazio, P. J. A., Badding, J. V. and Peacock, A. C. Nonlinear transmission properties of hydrogenated amorphous silicon core optical fibers, Optics Express, 18, 16826 (2010).
  • (21) Danisman, M.F, Calkins, J.A. Sazio, P.J.A., Allara, D.A., Badding, J.V. Organosilane Self Assembled Monolayer Growth from Supercritical Carbon Dioxide in Microstructured Optical Fiber Capillary Arrays, Langmuir, 24, 3636 (2008).
  • (22) Baril, N. F., Keshavarzi, B., Sparks, J. Krishnamurthi, M., Temnykh, I., Sazio, P. J. A., Peacock, A. C., Borhan, A., Gopalan, V., Badding, J. V. High Pressure Chemical Deposition for Void-Free Filling of Extreme Aspect Ratio Templates, Advanced Materials, 22, 4605 (2010).
  • (23) Jackson, B.R., Sazio, P.J., Badding,J.V., Single Crystal Silicon Wires Integrated into Microstructured Optical Fiber Templates, Advanced Materials, 20, 1135 (2008).
  • (24) Borkar, S., Gu, B., Dirmyer, M., Delicado, R., Sen, A., Jackson, B. R. & Badding, J. V. Polytetrafluoroethylene nano/microfibers by jet blowing. Polymer 47, 8337-8343 (2006).
  • (25) Ainslie, K. M., Bachelder, E. M., Borkar, S., Zahr, A. S., Sen, A., Badding, J. V. & Pishko, M. V.Albumin Adsorption and Cell Adhesion on Nanofibrous Polytetrafluoroethylene (nPTFE). Langmuir, 23, 747-754 (2007).