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The ability to fabricate materials, structures, devices, and systems with nanometer-scale precision is the key to obtain superior properties and performance. The scalability of lithographic approaches can promote them from research implementation to practical applications. My graduate research focuses on several unconventional lithographic techniques we have developed, which can create high-precision nanoscale patterns and three-dimensional (3D) hierarchical structures with high reproducibility, low cost, high throughput, and high precision.A hybrid patterning strategy called polymer-pen chemical lift-off lithography (PPCLL) was developed. We used pyramidal and v-shaped polymer-pen arrays for the sub-micron chemical patterning. By introducing the stamp support system and height gradients, we obtained linear-arrays of chemical patterns with linewidths ranging from sub-50 nm to sub-500 nm in sub-20 nm increments. We also showed our capability to tune feature size by controlling the compression distance. In doing so, we extended the patterning capability of PPCLL to generate more complex hollow patterns and gold nanorings. Self-collapse lithography (SCL) was another chemical lift-off lithography (CLL) based patterning technique. When elastomeric stamps with microscale relief features contacted with the self-assembled monolayer (SAM) functionalized substrates, the roof of the stamp collapses, resulting in the removal of SAM molecules in contact regions. With this technique, chemical patterns with feature size from ~2 �m to below 30 nm were obtained by decreasing stamp relief heights.We developed a robust and general strategy called multiple-patterning nanosphere lithography (MP-NSL) to fabricate periodic 3D hierarchical nanostructures in a highly scalable and tunable manner. The application of MP-NSL enables the fabrication of silicon nanotubes at the wafer scale with nanometer-scale control of outer diameter, inner diameter, height, hole-depth, and pitch. By adopting a multiple-patterning nanosphere lithography strategy, we are able to fabricate mechanically stable volcano-shaped nanostructures, called "nanovolcanos" with controllable heights, hole diameters/depths, and pitches. The sub-20-nm sharp features of nanovolcanos enable penetration of cell membranes and minimize disruption of cell functions. Biomolecular payloads containing the gene-editing packages are assembled and encapsulated into supramolecular nanoparticles. The holes (calderas) of the nanovolcanos can carry high payloads of biomolecular cargos that are readily accessed once cell membranes are penetrated.

Nanoribbon- and nanowire-based field-effect transistors (FETs) have attracted significant attention due to their high surface-to-volume ratios, which make them effective as chemical and biological sensors. However, the conventional nanofabrication of these devices is challenging and costly, posing a major barrier to widespread use. We report a high-throughput approach for producing arrays of ultrathin (∼3 nm) In2O3 nanoribbon FETs at the wafer scale. Uniform films of semiconducting In2O3 were prepared on Si/SiO2 surfaces via a sol-gel process prior to depositing Au/Ti metal layers. Commercially available high-definition digital versatile discs were employed as low-cost, large-area templates to prepare polymeric stamps for chemical lift-off lithography, which selectively removed molecules from self-assembled monolayers functionalizing the outermost Au surfaces. Nanoscale chemical patterns, consisting of one-dimensional lines (200 nm wide and 400 nm pitch) extending over centimeter length scales, were etched into the metal layers using the remaining monolayer regions as resists. Subsequent etch processes transferred the patterns into the underlying In2O3 films before the removal of the protective organic and metal coatings, revealing large-area nanoribbon arrays. We employed nanoribbons in semiconducting FET channels, achieving current on-to-off ratios over 107 and carrier mobilities up to 13.7 cm2 V-1 s-1. Nanofabricated structures, such as In2O3 nanoribbons and others, will be useful in nanoelectronics and biosensors. The technique demonstrated here will enable these applications and expand low-cost, large-area patterning strategies to enable a variety of materials and design geometries in nanoelectronics.

Nanoparticle alignment on the substrate attracts considerable attention due to its wide application in different fields, such as mechanical control, small size electronics, bio/chemical sensing, molecular manipulation, and energy harvesting. However, precise nanoparticle positioning and deposition control with high fidelity are still challenging. Herein, a straightforward strategy for high quality nanoparticle-alignment by chemical lift-off lithography (CLL) is demonstrated. This technique creates high resolution self-assembled monolayer (SAM) chemical patterns on gold substrates, enabling nanoparticle-selective deposition and precise alignment. The fabricated nanoparticle arrangement geometries and dimensions are well-controllable in a large area. With proper nanoparticle surface functionality control and adequate substrate molecular manipulation, well-defined nanoparticle arrays with single-particle-wide alignment resolution are achieved.

We demonstrate straightforward fabrication of highly sensitive biosensor arrays based on field-effect transistors, using an efficient high-throughput, large-area patterning process. Chemical lift-off lithography is used to construct field-effect transistor arrays with high spatial precision suitable for the fabrication of both micrometer- and nanometer-scale devices. Sol-gel processing is used to deposit ultrathin (∼4 nm) In2O3 films as semiconducting channel layers. The aqueous sol-gel process produces uniform In2O3 coatings with thicknesses of a few nanometers over large areas through simple spin-coating, and only low-temperature thermal annealing of the coatings is required. The ultrathin In2O3 enables construction of highly sensitive and selective biosensors through immobilization of specific aptamers to the channel surface; the ability to detect subnanomolar concentrations of dopamine is demonstrated.