Functional Hybrid Nanoarchitectures and Scalable Nanomanufacturing Technologies for Energy Conversion and Optoelectronics.

Abstract

Owing to their extraordinary ability to interacting with external stimuli as well as their versatile functionalities hardly observed in bulk systems, micro- and nano-scale materials, structures, and phenomena have been the subject of increasing interest from both academia and industry. Many diverse fields including optoelectronics, photonics, bioengineering, and energy conversion have all shown significant increases in utilization of, and need for, micro/nano-scale features. To meet this demand scalable, practical, and efficient methodologies for small-scale manufacturing are called for. This thesis work addresses these issues while focusing on three main topics: (1) how micro/nano-scale structures and materials can be integrated into hybrid assemblies that can combine their complementary functionalities and extend applicability; (2) how these functional nanoarchitectures can be engineered in a continuous and scalable manner to increase the manufacturing throughput; and (3) how those two approaches can be coupled to the scalable buildups of functioncal nanoarchitectures to facilitate practical applications ranging from energy converters to optoelectronics/photonics. More specifically, a 3D-hierarchical hybrid assembly of functional zinc oxide nanowires (ZNWs) and electrically addressable carbon nanotubes (CNTs) is developed and its application to photoelectric energy conversion is investigated. A series of continuous and scalable nanomanufacturing technologies follow, realizing high-speed (up to 1 m/min) patterning of small-scale features down to sub-100 nm resolution; Roll-to-Roll (R2R) process enables the continuous fabrication of large-area replica of desired pattern by continuously rolling the flexible master mold containing the counter-profiled pattern; NanoChannel-guided Lithography (NCL) can continuously create seamless and high aspect-ratio nanogratings by dynamically inscribing the cleaved grating mold edge at a tilted angle over the liquid resist-coated surface; finally, Vibrational Indentation-driven Patterning (VIP) accomplishes a template-free fabrication of micro/nano-scale gratings via the high-frequency periodic indenting of a ‘flat’ tool edge. The integrative scaling-up of functional nanodevices is then further implemented in two ways; first, the ZNW/CNT hybrids are processed into scalable thin film photodetectors via roll-processing, achieving rapid photoresponse (< 0.3s) and high external quantum efficiency (> 35%); second, Photo Roll Lithography (PRL) is developed by combining conventional photolithography and continuous rolling, which realizes high-throughput fabrication of geometrically-tunable sub-micron patterns for transparent electrodes and plasmonic IR filters.