Assembly and integration of semiconductor nanowires for functional nanosystems: From nanoelectronics to nanobiotechnology

Central to the bottom-up concept that could lead to entirely new and highly integrated functional nanosystems is the development of effective assembly methods that enable hierarchical organization of nanoscale building blocks over large areas. This thesis will focus on recent development of assembly approaches for organizing semiconductor nanowire (NW) building blocks and further integrating ordered structures to build functional device arrays. The applications of hierarchically assembled NW structures for constructing logic and memory arrays for nanocomputing system will be discussed, as well as the development of functional electronic interfaces between NW nanoelectronic arrays and biological systems.;In the thesis, I will first explore selective chemical interactions to drive the rational assembly of distinct semiconductor NWs onto dielectric substrates by design of complementary modifications between surfaces of NWs and substrates, including covalent bond, electrostatic and hydrogen bond interactions. Integrated arrays of silicon NWs and group II-VI NWs have been selectively assembled at well-defined locations on substrates, showing the potential of building structurally more complex nanosystems.;Second, I will present a novel strategy for preparing large-area, uniformly aligned and controlled-density NW and NT films by controlling bubble expansion of a homogeneous epoxy suspension containing these nanomaterials. The feasibility of this approach for nanodevice fabrication is demonstrated by large arrays of NWFETs on flexible plastics. This approach is further extended to novel polymer system with resist polymer PMMA as example to advance reproducible device fabrication of as-assembled nanomaterials. This represents one of the most critical advances necessary for realizing applications and efficient processing of these materials in electronics and optoelectronics.;Moreover, I will demonstrate significant advances made in building integrated nanoelectronic systems using NW crossbar arrays of assembled SiNWs and defined metal NWs, including high density memory arrays, Inverter, AND and NAND logic structures.;Last, I will discuss unique applications of assembled NW device arrays for studying functional nanoelectronic-biological interfaces by building well-defined nanowire-cell/tissue hybrid junctions, including highly integrated NW-neuron interface and multiplexed, flexible NW-heart tissue interface. Finally I will show recent progress on building novel NW device structures with flexible NW devices on perforated plastic substrates designed for improved device coupling with cells/tissues. NW nanoelectronic arrays thus provide a general and powerful platform for emerging nanobiotechnology.