ABEL-FRET: tether-free single-molecule FRET with hydrodynamic profiling

ABSTRACTSingle-molecule Förster resonance energy transfer (smFRET) has become a versatile and widespread method to probe nanoscale conformation and dynamics. However, current experimental protocols often resort to molecule immobilization for long observation times and rarely approach the resolution limit of FRET-based nanoscale metrology. Here we present ABEL-FRET, an immobilization-free platform for smFRET measurements with near shot-noise limited, Angstrom-level resolution in FRET efficiency. Furthermore, ABEL-FRET naturally integrates hydrodynamic profiling, which harnesses single-molecule diffusion coefficient to enhance FRET sensing of biological processes.

Plasmonic Nanofocusing in Deep and Extreme Sub-Wavelength Scale for Scalable Nanolithography

Maskless nanolithography is an agile and cost effective approach if their throughputs can be scaled for mass production purposes. Using plasmonic nanolithography approach, direct pattern writing was successfully demonstrated with 22 nm half-pitch at high speed. Plasmonic nanolithography uses an array of plasmonic lenses to directly pattern features on a rotating substrate. Taking the advantage of air bearing surface techniques, the system can expose the wafer pixel by pixel with a speed of ∼10 m/s, much faster than any conventional scanning based lithography system. It is a low-cost, high-throughput maskless approach for the next generation lithography and also for the emerging nanotechnology applications, such as nanoscale metrology and imaging. A critical part of the PNL is to use plasmonic lens to deliver highly concentrated optical power at nanoscale. We have demonstrated such nanoscale process and achieved 22 nm resolution. Here, we report our recent efforts of designing new plasmonic nanofocusing structures that is capable of achieving optical confinement below 20 nm which can potentially support direct patterning at sub-10nm resolution.

A Low-Cost, Automated Wafer Loading System With Submicron Alignment Accuracy for Nanomanufacturing and Nanometrology Applications

This paper introduces a low-cost, automated wafer alignment system capable of submicron wafer positioning repeatability. Accurate wafer alignment is critical in a number of nanomanufacturing and nanometrology applications where it is necessary to be able to overlay patterns between fabrication steps or measure the same spot on a wafer over and over again throughout the manufacturing process. The system presented in this paper was designed to support high-throughput nanoscale metrology where the goal is to be able to rapidly and consistently measure the same features on all the wafers in a wafer carrier without the need for slow and expensive vision-based alignment systems to find and measure the desired features. The wafer alignment system demonstrated in this paper consists of a three-pin passive wafer alignment stage, a voice coil actuated nesting force applicator, a three degrees-of-freedom (DOFs) wafer handling robot, and a wafer cassette. In this system, the wafer handling robot takes a wafer from the wafer cassette and loads it on to the wafer alignment stage. The voice coil actuator is then used to load the wafer against the three pins in the wafer alignment system and align the wafer to an atomic force microscope (AFM)-based metrology system. This simple system is able to achieve a throughput of 60 wafers/h with a positional alignment repeatability of 283 nm in the x-direction, 530 nm in the y-direction, and 398 nm in the z-direction for a total capital cost of less than $1800.

Scalable Plasmonic Nanolithography: Prototype System Design and Construction

Maskless nanolithography is an agile and cost effective approach if their throughputs can be scaled for mass production purposes. Using plasmonic nanolithography (PNL) approach, direct pattern writing was successfully demonstrated with around 20 nm half-pitch at high speed. Here, we report our recent efforts of implementing a high-throughput PNL prototype system with unique metrology and control features, which are designed to use an array of plasmonic lenses to pattern sub-100 nm features on a rotating substrate. Taking the advantage of air bearing surface techniques, the system can expose the wafer pixel by pixel with a speed of ∼10 m/s, much faster than any conventional scanning based lithography system. It is a low-cost, high-throughput maskless approach for the next generation lithography and also for the emerging nanotechnology applications, such as nanoscale metrology and imaging.

Compositional Mapping in Dynamic Atomic Force Microscopy in High-Q vs. Low-Q Environments: Effects of Cantilever Nonlinear Dynamics

The ability to simultaneously map variations in topography and composition (local stiffness, adhesion, charge, hydrophillicity/phobicity, viscoelasticity) of samples in ambient and liquid environments has made dynamic atomic force microscopy (dAFM) a powerful tool for nanoscale metrology. In ambient and vacuum environments, quality factors (Q-factors) of the fundamental resonance are typically large, and the contrast channels in dAFM are relatively well understood. In liquid environments, however, Q-factors are typically low due to cantilever interactions with the surrounding viscous liquid, which introduces a new class of nonlinear dynamics that is accompanied by new contrast channels, such as, higher harmonic amplitudes and phases. In particular, we find that the interpretation of the traditional contrast channels is quite different in low-Q environments compared to high-Q environments. We present a theoretical investigation of the contrast channels in dAFM in the context of frequency modulation and tapping mode dAFM with an emphasis on low-Q environments.