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|Zinc Oxide Nanowire Sensor Packaging|
|Keywords: Nanowires, Zinc Oxide, nanostructure|
|This paper describes two unique device topology packaging: single ZnO nanowire and array ZnO nanowire-based devices. Two device topologies have been fabricated and compared for their sensing performance. The single nanowire device has been fabricated through focused ion beam and e-beam lithography techniques while the SEM and EDAX analysis have been used to characterize the device. The IV characteristics of the ZnO nanowire- based array devices have been measured through a semiconductor parameter analyzer. Nanostructured materials have been extensively researched for a broad spectrum of applications. Especially, development and application of nanomaterials for chemical and biological sensing have been widely reported. The unique surface-related properties, with tunable size and shape-dependent physical and chemical properties, offer great potential for manipulating and improving sensing behavior. These characteristics have been demonstrated to aid in improving sensitivity and response rate of sensors. Maturity of synthesis techniques and availability of variety in terms of morphology and structure of these nanomaterials have provided immense flexibility to researchers for application-specific sensor development. These nanosensors have, therefore, proven to be quite useful in areas, such as environmental sensing, homeland security, vehicular emission control, industrial gas detectors, and biosensing. The ZnO nanowires for device fabrication were synthesized through a chemical vapor deposition process as explicated in our previous works. Briefly, ZnO nanowire growth resulted from the templated substrate (sapphire) due to vapor-liquid-solid (VLS) mechanism of nanowire growth at a temperature of 950°C. A single nanowire device was fabricated through extraction and manipulation of a nanowire from the ensemble of nanowires. This was accomplished by using micro- fabrication techniques of E-beam lithography and focused ion beam (FIB). First, inter-digitated electrodes on insulating sapphire substrates were made using E-beam lithography. The substrates were coated with 100 nm of positive resist (PMMA A2) at 4500 rpm for 45 seconds and were baked at 180°C for 90 seconds to make them adequate for the E-beam process. An inter-digitated pattern designed using CAD package with NPGS (Nanometer Pattern Generation System) was written on the resist-coated substrates. Two distinct device fabrication approaches were investigated to determine the most reliable topology of a field deployable ZnO nanosensor device for detecting p-nitrophenol vapors. First, a single ZnO nanowire device was fabricated with E-beam lithography and focused ion beam techniques. The EDAX analysis confirmed unintentional doping of Platinum in the sensing area during electrode deposition, which indicated contamination. Second, a multi-nanowire array approach for device fabrication was investigated.|
|Bruce Kim, Professor
City University of New York