Hierarchical nanostructure formation and applications using microfluidic system and microcontact printing technique

Abstract

Recently, development of functional devices using various nanostructures including nanowire, nanotube, and nanoparticles has been actively studied. The studies in this field are stimulated as many outstanding properties of electrical, optical, mechanical and chemical in nanoscale have been revealed. Using these properties, functional devices with much better performance can be achieved. Nanostructure synthesis methods can be basically divided into two methods which are top-down and bottom-up. Using the latter method, few nanometers to several tens of nanometer sized nanostructures can be fabricated easily without an additional lithography process, and therefore various functional nanostructures’ bottom-up synthesis methods are widely studied and developed. In this thesis, two kinds of techniques were investigated for the functional device fabrication. First, a microcontact printing technique was used for zinc oxide nanowire (ZnO NW) and functional materials aligned patterning. Second, the microfluidic systems were studied for zinc oxide nanoparticle (ZnO NP) synthesis and silver thin film formation. Each chapters of this thesis described the detailed fabrication process, related physical theories and results. Chapter 2 presents a novel and simple method for the patterned growth of ZnO NWs that combines (1) the direct patterning of ZnO NP seeds via microcontact printing and (2) subsequent low temperature hydrothermal growth. The ZnO NPs can be patterned as seed layers for ZnO NW growth on various substrates including flexible polymer films. The NW geometry and configuration can be controlled by varying the printing conditions (time and pressure) and the hydrothermal reaction time. To assess the possibility of high performance electronic applications of the patterned ZnO NWs, their field emission characteristics will be examined by fabricating a high performance field emission device with a patterned ZnO NW array. Chapter 3 described the developing a novel vacuu...