Nanoscale patterning is the key process to manufacture important products such as semiconductor microprocessors and data storage devices. Many studies have shown that it has the potential to revolutionize the functions of a broad range of products for a wide variety of applications in energy, healthcare, civil, defense and security. However, tools for mass production of these devices usually cost tens of million dollars each and are only affordable to the established semiconductor industry. A new method, nominally known as "pattern-on-the- y", that involves scanning an array of optical or electrical probes at high speed to form nanostructures and offers a new low-cost approach for nanoscale additive patterning. In this paper, we report some progress on using this method to pattern self-assembled monolayers (SAMs) on silicon substrate. We also functionalize the substrate with gold nanoparticle based on the SAM to show the feasibility of preparing amphiphilic and multi-functional surfaces.
Optically measuring temperature fields around plasmonic structures is of great importance for their thermal management considering the strong energy dissipations along with the extraordinary abilities of light coupling. Among all the available methods, ratiometric studies are particularly desirable since they suppress the influence of trivial factors, such as temporal fluctuations in excitation and spatial non-uniform distributions of fluorescent species, and thus gives reliable temperature dependence. Here we report a new ratiometric thermometry that simultaneously captures the fluorescence images of different numerical apertures (NAs) to resolve the temperature-dependent orientations of emission dipoles. This thermometry measures fluorescent anisotropy based on the directionality of emission. We show that this thermometry can be used to measure temperature near metallic surfaces. We foresee it to trigger interests of a large community who desire simultaneous thermal characterization along with the optical imaging. Moreover, it brings out a general idea to simplify ratiometric setups if inequalities exist on the excitation side, which may reach for a larger number of researchers.
Microcolumns are widely used for parallel electron-beam lithography because of their compactness and the ability to achieve high spatial resolution. A design of a large array of electrostatic microcolumns for our recent surface plasmon enhanced photoemission sources is optimized numerically. Because of the compactness, one million of microcolumns can be put within 1 cm2 area. To avoid the trade-off between resolution and throughput, each microcolumn has one beamlet and there is no crossing point between any of the beamlets. An aperture self-aligned fabrication process is developed to make the optimized microcolumns.
Maskless lithography using parallel electron beamlets is a promising solution for next generation scalable maskless nanolithography. Researchers have focused on this goal but have been unable to find a robust technology to generate and control high-quality electron beamlets with satisfactory brightness and uniformity.
In this work, we will aim to address this challenge by developing a revolutionary surface-plasmon-enhanced-photoemission (SPEP) technology to generate massively-parallel electron beamlets for maskless nanolithography. The new technology is built upon our recent breakthroughs in plasmonic lenses, which will be used to excite and focus surface plasmons to generate massively-parallel electron beamlets through photoemission. Specifically, the proposed SPEP device consists of an array of plasmonic lens and electrostatic micro-lens pairs, each pair independently producing an electron beamlet. During lithography, a spatial optical modulator will dynamically project light onto individual plasmonic lenses to control the switching and brightness of electron beamlets. The photons incident onto each plasmonic lens are concentrated into a diffraction-unlimited spot as localized surface plasmons to excite the local electrons to near their vacuum levels. Meanwhile, the electrostatic micro-lens extracts the excited electrons to form a focused beamlet, which can be rastered across a wafer to perform lithography. Studies showed that surface plasmons can enhance the photoemission by orders of magnitudes. This SPEP technology can scale up the maskless lithography process to write at wafers per hour. In this talk, we will report the mechanism of the strong electron-photon couplings and the locally enhanced photoexcitation, design of a SPEP device, overview of our proof-of-concept study, and demonstrated parallel lithography of 20-50 nm features.
Microcolumns are widely used for parallel electron-beam lithography because of their compactness and the ability to achieve high spatial resolution. A design of an electrostatic microcolumn for our recent nanoscale photoemission sources is presented. We proposed a compact column structure (as short as several microns in length) for the ease of microcolumn fabrication and lithography operation. We numerically studied the influence of several design parameters on the optical performance such as microcolumn diameter, electrode thickness, beam current, working voltages, and working distance. We also examined the effect of fringing field between adjacent microcolumns during parallel lithography operations. The microcolumns were also fabricated to show the possibility.
This work studied the optothermal response of plasmonic nanofocusing structures under picosecond pulsed laser
irradiation. The surface plasmon polariton is simulated to calculate the optical energy dissipation as the Joule heating
source and the thermal transport process is studied using a two temperature model (TTM). At the picosecond time scale
that we are interested in, the Fourier heat equation is used to study the electron thermal transport and the hyperbolic heat
equation is used to study the lattice thermal transport. For comparison, the single temperature model (STM) is also
studied. The difference between TTM and STM indicates that TTM provides more accurate estimates in the picosecond
time scale and the STM results are only reliable when the local electron and lattice temperature difference is negligible.