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    Item type:Publication, Access status: without files ,
    Universal and scalable fabrication of plasmonic nanocrystals for ultrasensitive SERS
    (ACS, 2026-05-10)
    Chirumamilla, Anisha
    ;
    Ding, Fei
    ;
    Krishnamurthy, Gnanavel V.
    ;
    Cai, Ziru
    ;
    Krekeler, Tobias
    Surface-enhanced Raman spectroscopy (SERS) enables the detection of molecular signatures at extremely low concentrations, even down to a single molecule, by using plasmonic nanostructures that support localized surface plasmon resonances (LSPRs). Nonetheless, fabricating highly sensitive nanostructures typically requires complex, time-consuming, and costly fabrication processes with limited scalability. In this work, we present a simple and universally applicable single-step method to fabricate plasmonic nanocrystals (NCs) from metals, such as Al, Ag, and Au. These NCs are directly grown over large surface areas on various substrates through heat-assisted growth from e-beam or magnetron sputter depositions. The LSPRs of the NCs can be tailored by selecting the metal, nanocrystal size, and surface morphology. The heat-assisted growth strategy enables the formation of NC matrices capable of detecting analyte molecules at ultralow, down to zeptomolar, concentrations via SERS, particularly when using Ag NCs. This versatile, cost-effective fabrication approach opens new opportunities for large-area plasmonic platforms in sensing, photocatalysis, and optoelectronic applications.
    Publicationtype: Journal Article
      18
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    Item type:Publication, Access status: with files ,
    Magnetron sputter deposition of nanostructured AlN thin films
    (Multidisciplinary Digital Publishing Institute (MDPI), 2023-10-05)
    Chirumamilla, Manohar
    ;
    Krekeler, Tobias
    ;
    Wang, Deyong
    ;
    Kristensen, Peter K.
    ;
    Ritter, Martin
    Aluminum nitride (AlN) is a material of growing interest for power electronics, fabrication of sensors, micro-electromechanical systems, and piezoelectric generators. For the latter, the formation of nanowire arrays or nanostructured films is one of the emerging research directions. In the current work, nanostructured AlN films manufactured with normal and glancing angle magnetron sputter depositions have been investigated with scanning and transmission electron microscopy, X-ray diffraction, atomic force microscopy, and optical spectroscopy. Growth of the nanostructures was realized utilizing metal seed particles (Ag, Au, and Al), allowing the control of the nucleation and following growth of AlN. It was demonstrated how variations of seed particle material and size can be used to tune the parameters of nanostructures and morphology of the AlN films. Using normal angle deposition allowed the growth of bud-shaped structures, which consisted of pillars/lamellae with wurtzite-like crystalline structures. Deposition at a glancing angle of 85° led to a film of individual nanostructures located near each other and tilted at an angle of 33 degree; relative to the surface normal. Such films maintained a high degree of wurtzite-like crystallinity but had a more open structure and higher roughness than the nanostructured films grown at normal incidence deposition. The developed production strategies and recipes for controlling parameters of nanostructured films pave the way for the formation of matrices to be used in piezoelectric applications.
    Publicationtype: Journal Article
      20  91
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    Item type:Publication, Access status: with files ,
    Spectrally selective emitters based on 3D Mo nanopillars for thermophotovoltaic energy harvesting
    (Elsevier, 2021-08-10)
    Chirumamilla, Anisha
    ;
    Yang, Yuanqing
    ;
    Salazar, Maria H.
    ;
    Ding, Fei
    ;
    Wang, Deyong
    High-temperature stable emitters with spectral selective functionality are an absolute condition for efficient conversion of thermal radiation into electricity using thermophotovoltaic (TPV) systems. Usually, spectral selective emitters are made up of multilayered materials or geometrical structures resulting from complex fabrication processes. Here, we report a spectrally selective emitter based on a single metal layer coating of molybdenum (Mo) over a 3D dielectric pillar geometry. 3D Mo nanopillars are fabricated using large-area and cost-effective hole-mask colloidal lithography. These nanostructures show an absorptivity/emissivity of 95% below the cut-off wavelength of an InGaAsSb PV cell at 2.25 μm, and a sharp decline in absorptivity/emissivity in the near-infrared regions, approaching a low emissivity of 10%. The 3D Mo nanopillars show outstanding thermal/structural stability up to 1473 K for 24 h duration under Ar atmosphere and polarization and angle invariance up to 60° incidence angles. With a low-cost and scalable fabrication method, 3D Mo nanostructures provide tremendous opportunities in TPV and high temperature photonic/plasmonic applications.
    Publicationtype: Journal Article
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