This thesis focuses on nanomanufacturing processes for the heterogeneous integration of nanomaterials and molecules. We demonstrate and discovered a novel gas phase method to control material flux at specific points on a surface which is based on the interplay of high mobility gas ions and lower mobility nanoparticles and molecules in the presence of a patterned substrate. The thesis is divided into two parts describing applications of the discovered process for the localized deposition of
(A) metallic and semiconducting particles producing functional nanostructured deposits including multimaterial sensor arrays and nanostructured electrodes for photovoltaic applications and,
(B) molecules for gas sensor application demonstrating improved collection efficiencies and sensitivity over previously methods.
Section (A) begins with the description of an arc discharge based method to produce a flux of charged nanoparticles (<5nm particles Au, Ag, Pt, W, TiO2, ZnO and Ge) which are characterized using various methods. It then describes a process to locally deposit the charged particles into extended two and three dimensional metallic and semiconducting nanostructured deposits. The thesis describes the use externally-biased electrodes to achieve an electronic shutter to turn ON/OFF the deposition in selected domains. Subsequently it explores and describes the use of patterned dielectrics whereby the patterned dielectrics are charged to define arrays of electrodynamic lenses. Incorporation of these lensing structures was found to enable nanostructured deposits with sub 100nm lateral resolution. The utility of the discovered processes are demonstrated in two areas. For the first application, semiconducting nanomaterial are sequentially deposited on the same substrate to fabricate a multi-material / multi-functional sensor array on a single substrate in a single deposition process. The process eliminates critical alignment and masking steps and has a higher material efficiency when compared with traditional vapor deposition methods. In the second application, we demonstrate the fabrication of 3D nanostructured electrodes for photovoltaic application. The second application adjusts the material flux in selected domains to identify nanostructures and device metrics in a combinatorial way. Section (B) applies the process to the localized collection of airborne molecules. The goal was to determine if the process can be scaled to particles with molecular dimensions. This turned out to be the case. As an application we demonstrate enhanced collection efficiencies of molecular species in gas sensor applications. The research recognizes that various nanostructured sensor designs currently aim to achieve or claim single molecular detection by a reduction of the active sensor size. However, a reduction of the sensor size has the negative effect of reducing the capture probability considering the diffusion based analyte transport commonly used. Specifically, we applied the discovered localized programmable electrodynamic precipitation concept to collect, spot, and detect airborne species in an active-matrix array-like fashion. The method is tested using surface enhanced Raman spectroscopy (SERS). The process can produce hybrid molecular arrays on a single chip over a broad range of molecular weights including small molecules or large macromolecules. From a gas sensor system point of view it was possible to improved collection efficiencies and sensitivity over previously method.
University of Minnesota Ph.D. dissertation. April 2013. Major: Electrical Engineering. Advisor: Heiko O. Jacobs. 1 computer file (PDF); vii, 84 pages.
Localized programmable gas phase electrodeposition yielding functional nanostructured materials and molecular arrays.
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