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| Advanced Probes for Nano-Scale Chemical Characterization |
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| Objective: |
| Commercial incorporation of Nanoscale technology faces major hurdles in terms of suitable measurement methods to determine the composition, structure, and performance of products that incorporate nanotechnology. This program will develop measurement methods and data reduction algorithms that will enable industry to assess the nanoscale aspects critical to the realization of nanotechnology. |
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| Description: |
| The need for improved spatial resolution currently limits the ability of Industry to answer key questions regarding the chemical composition of surfaces and interfaces. Needs range from improved chemical and structural diagnostics to phase identification and trace compositional analysis. In addition to meeting current industry needs in these areas, there is a continuing demand for new measurement methods to be developed that will be positioned to meet emerging measurement challenges. The Division develops measurement tools that enable the chemical characterization (elements, isotopes, and molecules) at millimeter to nanometer spatial scales with major, minor, and trace concentrations. We strive to develop measurement tools such that the ‘microspatial' relationships of chemical species can be correlated with specific macroscopic properties. Examples are: Raman near-field methods; dielectric near-field probes; theoretical and experimental measurement basis for near-field (tunneling and evanescent) nano-scale probes; assessment tools that are amenable to image-based data structures; bring electron microscopy to the full realization of nanoscale resolution; establish measurement science that will allow advance detector concepts to be incorporated into electron microscopes to enable compositional and structural changes to be characterized at the nanoscale; and develop SIMS methods that reduce sample damage and increase sensitivity. |
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| Area(s) of Application: |
- Electronics
- Industrial and Analytical Instruments
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| Accomplishments: |
The Division has leveraged its strong capabilities in scanned probes, electron microscopy, non-linear optical methods, and photoemission in collaborative efforts with MSEL, PL and other Divisions within CSTL.
- Horizontal Growth and In Situ Assembly of Oriented Zinc Oxide Nanowires: This methodology will provide an inexpensive and straightforward approach to the synthesis of semiconducting, nanodevices (emitters and detectors) with multiple functionalities that can be integrated to form state-of-the-art measurement systems. Our studies have focused on the growth and manipulation of semiconductor ZnO nanowires.
- Controlling "injection barriers" into prototype molecular wires through substrate coupling chemistry : Self-assembly of monolayers utilizing thiol chemistry is known to form robust, reproducible monolayers on a variety of metallic surfaces, however the surface characteristics are not well known. Thus, we have undertaken a study of understanding how the band line-up varies as a function of changing the linking chemistry between the molecule and the surface. These studies have demonstrated that there are large variations, which will have a major impact on charge injection in molecular systems. Models have been developed that help explain the observed behavior.
- Nanofabrication of Test Architectures for Molecular Electronics Applications : The CSTL research team developed a robust, systematic, nanoscale test structure to critically evaluate electrical properties of candidate material that are used in the development of nanoscale molecular-based electronic devices. We also found that well-defined nanoscale metal-metal junctions can be formed which may be employed in the development of enhanced optical spectroscopic methods for sensing.
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| Future Plans: |
- Growth of Nanowires: These methodologies are being implemented in the fabrication of heterostructured (ZnO/GaN) nanowires for use as nano-emitting sources (laser diodes) and nano-detectors (photodiodes) with emphasis on optical properties and performance suited for applications in sensing and spectrochemical analysis.
- Controlling “injection barriers” in molecular wires: We will build upon our previous studies of understanding the affect molecular structure and linking-group chemistry have on controlling band line-up in covalently bound molecular systems. Our future work will focus on varying the metal onto which the molecule is adsorbed, as well as alkali metal doping of monolayer films.
- Nanofabrication for Molecular Electronics: Ongoing experiments are now aimed at probing the electrical behavior of ensembles of molecules within the nanopatterned junctions. These measurements can then be compared to those from prototypical device structures. This approach for building nanopatterned metallic structures will also be transferred to Si substrates as a means to construct hybrid semiconductor-molecule-metal junctions.
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| Recent publications: |
- Nikoobakht B., Michaels C.A. , S.J. Stranick, and Vaudin, M.D. “ Horizontal Growth and in situ Assembly of Oriented Zinc Oxide Nanowires”, Appl. Phys. Lett. 85 , 3244 (2004).
- Michaels, C.A., Chase, D.B., and Stranick, S.J. “ Chemical Imaging of Heterogeneous Polymeric Materials with Near-Field IR Microscopy ,” Applications of Scanned Probe Microscopy to Polymers” Batteas, J.D, Michaels C.A., Walker, G.C., Eds. ACS Symposium Series, Vol. 897, 38-50 , 2005.
- Nikoobakht, B., and Batteas, J.D., “ Selective Growth of Zinc Oxide Nanodots and Nanowires on Silicon ,” Journal of Physical Chemistry, (in press).
- Nikoobakht, B., Davydov, A.V., Stranick, S.J., “Growth of Vertical ZnO Nanowires on c-plane Sapphire,” Journal of Advanced ???, 2004, (in press).
- Stranick, S.J., Chase, D.B., and Michaels, C.A. , “Chemical Imaging with Scanning Near-Field Microscopy and Spectroscopy,” Rubber Chemistry and Technology (in press).
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| Other related project work: |
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| Principal Investigator: Richard Cavanagh |
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