• Login
    View Item 
    •   Home
    • Theses and Dissertations
    • Theses and Dissertations
    • View Item
    •   Home
    • Theses and Dissertations
    • Theses and Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of TUScholarShareCommunitiesDateAuthorsTitlesSubjectsGenresThis CollectionDateAuthorsTitlesSubjectsGenres

    My Account

    LoginRegister

    Help

    AboutPeoplePoliciesHelp for DepositorsData DepositFAQs

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    A Close-Space Sublimation Driven Pathway for the Manipulation of Substrate-Supported Micro- and Nanostructures

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    TETDEDXSundar-temple-0225E-118 ...
    Size:
    3.680Mb
    Format:
    PDF
    Download
    Genre
    Thesis/Dissertation
    Date
    2014
    Author
    Sundar, Aarthi
    Advisor
    Neretina, Svetlana
    Committee member
    Cohen, Richard
    Hughes, Robert
    Sheffield, Joel B.
    Zhang, Huichun (Judy)
    Department
    Mechanical Engineering
    Subject
    Nanotechnology
    Nanoscience
    Dewetting
    Epitaxy
    Eutectic
    Nanocrescents
    Plasmonics
    Surface-energy
    Permanent link to this record
    http://hdl.handle.net/20.500.12613/3617
    
    Metadata
    Show full item record
    DOI
    http://dx.doi.org/10.34944/dspace/3599
    Abstract
    The ability to fabricate structures and engineer materials on the nanoscale leads to the development of new devices and the study of exciting phenomena. Nanostructures attached to the surface of a substrate, in a manner that renders them immobile, have numerous potential applications in a diverse number of areas. Substrate-supported nanostructures can be fabricated using numerous modalities; however the easiest and most inexpensive technique to create a large area of randomly distributed particles is by the technique of thermal dewetting. In this process a metastable thin film is deposited at room temperature and heated, causing the film to lower its surface energy by agglomerating into droplet-like nanostructures. The main drawbacks of nanostructure fabrication via this technique are the substantial size distributions realized and the lack of control over nanostructure placement. In this doctoral dissertation, a new pathway for imposing order onto the thermal dewetting process and for manipulating the size, placement, shape and composition of preformed templates is described. It sees the confinement of substrate-supported thin films or nanostructure templates by the free surface of a metal film or a second substrate surface. Confining the templates in this manner and heating them to elevated temperatures leads to changes in the characteristics of the nanostructures formed. Three different modalities are demonstrated which alters the preformed structures by: (i) subtracting atoms from the templates, (ii) adding atoms to the template or (iii) simultaneously adding and subtracting atoms. The ability to carry out such processes depends on the choice of the confining surface and the nanostructured templates used. A subtractive process occurs when an electroformed nickel mesh is placed in conformal contact with a continuous gold film while it dewets, resulting in the formation of a periodic array of gold microstructures on an oxide substrate surface. When heated the gold beneath the grid selectively attaches to it due to the surface energy gradient which drives gold from the low surface energy oxide surface to the higher surface energy nickel mesh. With this process being confined to areas adjacent to and in contact with the grid surface the film ruptures at well-defined locations to form isolated islands of gold and subsequently, a periodic array of microstructures. The process can be carried out on substrates of different crystallographic orientations leading to nanostructures which are formed epitaxially and have orientations based on underlying substrate orientations. The process can be extended by placing a metallic foil of Pt or Ni over preformed templates, in which case a reduction in the size of the initial structures is observed. Placing a foil on structures with random placement and a wide size distribution results, not only in a size reduction, but also a narrowed size distribution. Additive processes are carried out by using materials which possess high vapor pressures much below the sublimation temperature of the template materials. In this case a germanium substrate was used as a source of germanium adatoms while gold or silver nanostructures were used as heterogeneous nucleation sites. At elevated temperatures the adatoms collect in sufficient quantities to transform each site into a liquid alloy which, upon cooling, phase separates into elemental components sharing a common interface and, hence, resulting in the formation of heterodimers and hollowed metal nanocrescents upon etching away the Ge. A process which combined aspects of the additive and subtractive process was carried out by using a metallic foil with a high vapor pressure and higher surface energy than the substrate surface (in this case Pd foil). This process resulted in the initial preformed gold templates being annihilated and replaced by nanostructures of palladium, thereby altering their chemical composition. The assembly process relies on the concurrent sublimation of palladium and gold which results in the complete transfer of the templated gold from the substrate to the foil, but not before the templates act as heterogeneous nucleation sites for palladium adatoms arriving to the substrate surface. Thus, the process is not only subtractive, but also additive due to the addition of palladium and removal of gold.
    ADA compliance
    For Americans with Disabilities Act (ADA) accommodation, including help with reading this content, please contact scholarshare@temple.edu
    Collections
    Theses and Dissertations

    entitlement

     
    DSpace software (copyright © 2002 - 2023)  DuraSpace
    Temple University Libraries | 1900 N. 13th Street | Philadelphia, PA 19122
    (215) 204-8212 | scholarshare@temple.edu
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.