Stephen Y Chou

• PhD
• Head of Department at Princeton University

Sensitive detection of pathogens is crucial for early disease diagnosis and quarantine, which is of tremendous need in controlling severe and fatal illness epidemics such as of Ebola virus (EBOV) disease. Serology assays can detect EBOV‐specific antigens and antibodies cost‐effectively without sophisticated equipment; however, they are less sensiti...

This disclosure provides, among other things, a nanosensor comprising a substrate and one or a plurality of pillars extending from a surface of the substrate, where the pillars comprise a metallic dot structure, a metal disc, and a metallic back plane. The nanosensor comprises a molecular adhesion layer that covers at least a part of the metallic d...

Microstructures and nanostructures (100) consisting of a substrate (110), an array of pillars (120) capped by metallic disc (130), metallic dots (clusters or granules) (140) disposed on the sidewalls of the pillars, and a metallic backplane (150) that can interact to enhance a local electric field, the absorption of the light, and the radiation of...

Sapphire nanopatterning is the key solution to GaN light emitting diode (LED) light extraction. One challenge is to etch deep nanostructures with a vertical sidewall in sapphire. Here, we report a study of the effects of two masking materials (SiO2 and Cr) and different etching recipes (the reaction gas ratio, the reaction pressure and the inductiv...

The lithium ion battery, a preferred energy storage technology, is limited by its volumetric and gravimetric energy densities, as well as its capacity retention with prolonged cycling. In this work, the authors exploited the extremely high lithium storage capacity of Si as an anode material and tackled the issue of lithium-induced volume expansion...

A method and apparatus for performing nanoimprint lithography. When an electric field is applied between the mold and the substrate, various forces can be generated among molds, substrates, and resists. The electrostatic force between the mold and the substrate can serve as an imprinting pressure to press the structured mold into the conformable re...

One central challenge in LEDs is to increase light extraction; but for display applications, other factors may have equal significance, such as ambient-light absorption, contrast, viewing angle, image sharpness, brightness, and low-glare. However, current LED structures enhance only some of the factors, while degrading the others. Here, a new organ...

Efficient capture of sunlight remains one of the great challenges to photovoltaics today. This is particularly so for the dominant photovoltaic material - crystalline silicon - which, as an indirect gap semiconductor, needs several hundred micrometers thickness for efficient operation. This paper gives an overview of the principal concepts that are...

We propose and experimentally demonstrate a new plasmonic nonlinear light generation (NLG) structure, termed "Plasmonic-enhanced, Charge-Assisted Second-Harmonic generator" (p-CASH), that not only achieves high second-harmonic generation (SHG) enhancement (76-fold), large SHG tunability by bias (8%/V), wide tuning range (280%), 7.8×10-9 conversion...

We report the structure, performance and large-area fabrication of a thin plasmonic infrared absorber, termed "bar-shaped disk-coupled dots-on-pillar antenna-array" (bar-D2PA). The bar-D2PAs, which are simple to fabricate, demonstrate experimentally: (i) a different light-absorption resonance for each polarization with the resonance peak tunable by...

This talk focuses on nanoimprinting, a revolutionary approach to fabrication that not only makes new kinds of devices conceivable, but also makes it possible to manufacture them economically. Key technologies will be explained and illustrated, particularly in connection with devices for energy harvesting. A central example is a new solar cell struc...

The invention is directed to new nanoimprint resist and thin-film compositions for use in nanoimprinting lithography. The compositions permit economical high-throughput mass production, using nanoimprint processes, of patterns having sub-200 nm, and even sub-50 nm features.

We demonstrate a new way to electrically tune the self-oscillation frequency of an external cavity VCSEL by changing the electrical current injected into the VCSEL, without using any mechanical moving parts. We found that for a self-oscillation frequency from 500 MHz to 4 GHz, the tuning range is up to 15% and the tuning rate is up to 800 MHz/mA. O...

Three of central challenges in solar cells are high light coupling into solar cell, high light trapping and absorption in a sub-absorption-length-thick active layer, and replacement of the indium-tin-oxide (ITO) transparent electrode used in thin-film devices. Here, we report a proposal and the first experimental study and demonstration of a new ul...

New technologies for large-area 3D-nanopatterning using nanoimprint and self-perfection, and new 3D nanoplasmonic structures have been developed and applied to drastically enhance performance of sensors (fluorescence and Raman by orders of magnitude) and solar cells.

We demonstrated a continuous frequency tuning of fluorescence enhancement spectra using 3D plasmonic nanocavities with accurately controlled resonance frequencies based on the Moiré pattern created by a double-Nanoimprint based technique.

We report a 310-fold upconversion luminescence enhancement, and 8-fold decay rate enhancement of NaYF4:Yb3+/Er3+ codoped nanocrystals using a 3D plasmonic nanoantenna array. The enhancement is two orders of magnitude larger than previously reported results.

We present and demonstrate a novel fabrication method to integrate metallic nanostructures into fluidic systems, using nanoimprint lithography and lift-off on a compositional resist stack, which consists of multi-layers of SiO(2) and polymer patterned from different fabrication steps. The lift-off of the stack allows the final nano-features precise...

Plasmon-enhanced upconversion luminescence of NaYF4: Yb(3+) /Er(3+) co-doped nanocrystals is investigated using a 3D plasmonic antenna architecture: a disk-coupled dots-on-pillar antenna array (D2PA). By tuning and optimizing the resonance frequency of the D2PA structure for upconversion luminescence, a 310-fold luminescence enhancement and an 8-fo...

Quantum lithography (QL) is a revolutionary approach to significantly increase the throughput and lower the cost of electron beam lithography in writing large-area masks with nanoscale features. A major challenge in QL is that its principle can be readily applied to positive- but not negative-tone QL. In fact, negative-tone QL, which is as indispen...

We report a tri-layer method that offers excellent lift-off of copolymer and pattern transfer on wafer scale. We achieved 34 nm pitch, ~17 nm diameter metal dots after lift-off. In addition, we used those dots to fabricate a wafer scale nanoimprint mold consisting of 0.6 T/in2, 50 nm high pillars.

Using a new nanoplasmonic architecture and an optimized spacer, we observed the following: (a) the average fluorescence of an infrared dye (indocyanine green) is enhanced by 2970 fold uniformly (variation < 11%) over a large sample area and over a wide range of dye concentrations (380 to 380 000 molecule µm(-2)), laser excitation powers and laser b...

Protein detection is universal and vital in biological study and medical diagnosis (e.g., cancer detection). Fluorescent immunoassay is one of the most widely used and most sensitive methods in protein detection (Giljohann, D. A.; Mirkin, C. A. Nature2009, 462, 461-464; Yager, P.; et al. Nature2006, 442, 412-418). Improvements of such assays have m...

We studied the extraordinary light transmission through opaque thin metal film with subwavelength holes blocked by metal disks. The maximum transmission is achieved when the disk diameter is around 80 nm even with different hole diameters.

We report strong fluorescence emissions from single IR dye molecules on a novel 3D plasmonic nanoantenna array. The measured emission cross-section is ~1E-13 cm2, 5 orders of magnitude than the value in solution.

We report a new approach, termed "growth by nanopatterned host-medicated catalyst" (NHC growth), to solve nonuniformities of Si nanowires (NWs) grown on amorphous substrates. Rather than pure metal catalyst, the NHC uses a mixture of metal catalyst with the material to be grown (i.e., Si), nanopatterns them into desired locations and anneals them....

Nano-graphene ribbons are promising in many electronic applications, as their bandgaps can be opened by reducing the widths, e.g. below 20 nm. However, a high-throughput method to pattern large-area nano-graphene features is still not available. Here we report a fabrication method of sub-20 nm ribbons on graphite stamps by nanoimprint lithography a...

We observed that when subwavelength-sized holes in an optically opaque metal film are completely covered by opaque metal disks larger than the holes, the light transmission through the holes is not reduced, but rather enhanced. Particularly we report (i) the observation of light transmission through the holes blocked by the metal disks up to 70% la...

Nano-patterned sapphire substrate with sub-wavelength pattern pitch (200nm) was fabricated to enhance the poor extraction efficiency of GaN LED. Such substrate can give 80% more light out, better than previously-reported micro-scale pattern.

We propose and demonstrate a new SERS substrate architecture that couples a dense three-dimensional (3-D) cavity nanoantenna array, through nano-gaps, with dense plasmonic nanodots; and a new nanofabrication that combines nanoimprint, guided self-assembly and self-alignment and has fabricated the architecture precisely, simply, inexpensively and ov...

We demonstrated the tuning of the self-oscillation frequency of an external cavity VCSEL using drive current. This frequency tuning occurs for all cavity lengths constructed; however, the degree of frequency tuning correlates with cavity length.

In this paper, we address the hydraulic flow of fluids on and within nanofabricated hydrophilic (as opposed to hydrophobic) surfaces, and the influence of an extended precursor film on the wetting dynamics of water penetrating a nano-textured array of posts that has no sealing surface (open-top). The width of the precursor film in front of the wett...

Contains reports on sixteen research projects.

Contains reports on fourteen research projects.

Contains reports on thirteen research projects.

Typically, nanopatterning on plastic substrates has poor fidelity, poor adhesion, and low yield. Here the proposal of and the first experiment using a new fabrication method that overcomes the above obstacles and has achieved arrays of 60-nm-diameter, perfectly round metal dots over a large area on a polyethylene terephthalate (PET) substrate with...

We study effects of nanodots on surface plasmons and field enhancement in nano-pillar antenna array. The NPA’s nanodots have slight effect on surface plasmon resonance wavelength, but increase field enhancement by two orders of magnitude.

We demonstrate subwavelength resonant grating mirrors made from III-V semiconductor materials for the mid-infrared. We achieved a resonance wavelength at ∼3µm which agrees very well with simulated data, and measured a spectral width of ∼30nm.

We designed, fabricated and demonstrated a solar-blind deep-UV pass filter, that has a measured optical performance of a 27% transmission peak at 290 nm, a pass-band width of 100 nm (from 250 to 350 nm), and a 20dB rejection ratio between deep-UV wavelength and visible wavelength. The filter consists of an aluminum nano-grid, which was made by coat...

A wafer-scale (∼4 inch) 100 nm nano-checkerboard structure was fabricated. The fabrication combines multiple nanoimprint lithography, 3-D patterning and self-aligned etching. Transmission/reflection resonance at ∼750 nm and Raman enhancement of ∼ 4.5×106 were achieved.

Fabrication of an asymmetric source/drain structure is important to heterojunction tunneling transistors but is extremely difficult to achieve reliably due to the stringent requirement of nanometer overlay alignment. Here the authors propose and demonstrate a simple self-aligned asymmetric nanotrench fabrication method, which has achieved a 10 nm w...

We report a method of one-step direct patterning of metallic nanostructures. In the method, termed laser assisted direct imprinting (LADI), the surface of a metal film on a substrate is melted by a single excimer laser pulse and subsequently imprinted within approximately 100 ns using a transparent quartz mold, while the substrate is kept at a low...

We proposed and demonstrated a new approach to pressed self-perfection by liquefaction (P-SPEL), where a layer of SiO2 is used as a stopper on one sidewall of gratings, to self-limit the final trench width in P-SPEL to a preset stopper layer thickness, allowing a precise control of the final trench width without the need to control any pressing pa...

We use a novel technique, self-perfection by liquefaction (SPEL), to smooth the rough sidewalls of Si waveguides. An XeCl excimer laser with 308 nm wavelength and 20 ns pulse duration is used to selectively melt the surface layer of the waveguide. This molten layer flows under surface tension and this results in smooth sidewalls upon resolidificati...

We propose and demonstrate a new method for fabricating periodic arrays of metal nanodots over a large area. In this method, metal nanogratings were first patterned on a substrate by nanoimprint lithography and lift-off, and were then melted using a single excimer laser pulse. We found that the laser melting broke the metal nanogratings into period...

A novel method for fabricating nanoimprint lithography (NIL) molds for T-shaped gates (T-gates) for high speed transistors is proposed and demonstrated. This method uses NIL, low pressure chemical vapor deposition and reactive ion etching processes, and avoids costly electron beam lithography and high accuracy alignment technology. Using the T-gate...

We demonstrated an external cavity vertical-cavity-surface-emitting-laser (VCSEL) clock using a subwavelength quarter-wave plate and achieved a polarization self-switching frequency as high as 7.2 GHz with an oscillation frequency FWHM of 6 MHz.

Quantum lithography (QL) is a revolutionary approach, increasing the throughput and lowering the cost of scanning electron beam lithography (EBL). But it has not been pursued since its inception 17 years ago, due to the lack of a viable method for making the blanks needed. Here we propose and demonstrate a new general viable approach to QL blank fa...

This paper addresses novel applications of an excimer laser (308nm wavelength, 20ns pulse duration) in nanofabrication. Specifically, laser assisted nanoimprint lithography (LAN), self-perfection by liquefaction (SPEL), fabrication of metal nanoparticle arrays, and the fabrication of sub-10-nm nanofluidic channels are covered. In LAN, a polymeric r...

We report a new method to fabricate self-enclosed optically transparent nanofluidic channel arrays with sub-10 nm channel width over large areas. Our method involves patterning nanoscale Si trenches using nanoimprint lithography (NIL), sealing the trenches into enclosed channels by ultrafast laser pulse melting and shrinking the channel sizes by se...

Self-perfection by liquefaction (SPEL) was used to fabricate nanoimprint molds with an array of sub-25 nm diameter pillars (200 nm period), resulting in nearly perfect cylindrical shape and smooth sidewalls. SPEL turned an array of irregularly shaped Cr polygons into an array of nearly perfect circular dots with small diameter. The Cr dot arrays we...

We present a versatile method for continuous-flow, on-chip biological processing of cells, large bio-particles, and functional beads. Using an asymmetric post array in pressure-driven microfluidic flow, we can move particles of interest across multiple, independent chemical streams, enabling sequential chemical operations. With this method, we demo...

We demonstrate wide-area fabrication of sub-40 nm diameter, 1.5 µm tall, high aspect ratio silicon pillar arrays with straight sidewalls by combining nanoimprint lithography (NIL) and deep reactive ion etching (DRIE). Imprint molds were used to pre-pattern nanopillar positions precisely on a 200 nm square lattice with long range order. The conventi...

The authors have developed an approach to fabricate sharp and high aspect ratio metal tips using nanosecond pulse laser melting. A quartz wafer covered with a thin chromium (Cr) film was placed on top of a second wafer with a sub-micrometer gap between them and the Cr film facing the second wafer. Then an excimer laser pulse (308 nm wavelength, 20...

We report a new approach to adjust and improve nanostructures after their initial fabrication, which can reduce the trench width and hole diameter to sub-10 nm, while smoothing edge roughness and perfecting pattern shapes. In this method, termed pressed self-perfection by liquefaction (P-SPEL), a flat guiding plate is pressed on top of the structur...

A challenge in nanofabrication is to overcome the limitations of various fabrication methods, including defects, line-edge roughness and the minimum size for the feature linewidth. Here we demonstrate a new approach that can remove fabrication defects and improve nanostructures post-fabrication. This method, which we call self-perfection by liquefa...

We show that it is possible to direct particles entrained in a fluid along trajectories much like rays of light in classical optics. A microstructured, asymmetric post array forms the core hydrodynamic element and is used as a building block to construct microfluidic metamaterials and to demonstrate refractive, focusing, and dispersive pathways for...

We report fabrication and characterization of a novel real-time, label-free DNA detector, that uses a long nanofluidic channel to stretch a DNA strand and a nanogap detector (with a gap as small as 9 nm) inside the channel to measure the electrical conduction perpendicular to the DNA backbone as it moves through the gap. We have observed electrical...

A challenge in nanofabrication is to overcome the limitations of various fabrication methods, including defects, line-edge roughness and the minimum size for the feature linewidth. Here we demonstrate a new approach that can remove fabrication defects and improve nanostructures post-fabrication. This method, which we call self-perfection by liquefa...

This paper presents a novel method to parallel fabricate large area (wafer scale) metallic nano-split-ring arrays with nanoimprint lithography (NIL). To our knowledge it is the first method that can pattern large area and high dense metallic split-ring arrays with advantages of high throughput, low-cost and simplicity. This method makes metallic na...

Directing objects across functional streamlines at low Reynolds number is difficult but important since this motion can be used to label, lyse, and analyze complex biological objects on-chip without cross-contamination. Here we use an asymmeteric post array to move cells across coflowing reagents and show on-chip, immunofluorescent labeling of plat...

For all technologies, from flint arrowheads to DNA microarrays, patterning the functional material is crucial. For semiconductor integrated circuits (ICs), it is even more critical than for most technologies because enormous benefits accrue to going smaller, notably higher speed and much less energy consumed per computing function. The consensus is...

We report and demonstrate a new method to fabricate single fluidic-channels of uniform channel width (11-50 nm) and over 1.5 cm in length, which are essential to developing innovative bio/chemical sensors but have not been fabricated previously. The method uses unconventional nanofabrication (a combination of crystallographic anisotropic etching, c...

This chapter describes the principle of nanoimprint lithography, different nanoimprint forms and their relative merits and shortcomings, key factors in nanoimprinting (masks, materials, pressing methods and imprinting pressure uniformity, material dispensing methods, vacuum, mold separation), examples of nanoimprinting in magnetic nanostructure fab...

Summary form only given. Since the proposal of nanoimprint lithography (NIL) as a low-cost high-throughput sub-10-nm manufacturing method in 1995, the field has been growing rapidly in research, applications and commercialization in the past 12 years. The talk will first address some advances in nanoimprint technology, tools, applications and comme...

We demonstrate a method that uses the pillars on a stamp to cut and exfoliate graphene islands from a graphite and then uses transfer printing to place the islands from the stamp into the device active-areas on a substrate with a placement accuracy potentially in nanometers. The process can be repeated to cover all device active-areas over an entir...

We demonstrate a tunable filter consisting of a subwavelength resonant grating filter cladded by a liquid crystal cell. The resonant wavelength of the grating filter is tuned by electrically varying the refractive index of the liquid crystal. A tuning range of around 20 nm has been achieved.

Periodic micro- and nanostructures (gratings) have many significant applications in electronic, optical, magnetic, chemical and biological devices and materials. Traditional methods for fabricating gratings by writing with electrons, ions or a mechanical tip are limited to very small areas and suffer from extremely low throughput. Interference lith...

In this paper an optical system is integrated on a chip and fabricated monolithically. The two new platform technologies besides guided-wave integrated optics are discussed. Subwavelength optical elements (SOEs), a new class of optical devices well suited for wafer level integration, and nanoimprint technology an enabling nanopatterning method. To...

We demonstrate a tunable external cavity laser consisting of a voltage-tuned liquid-crystal cladded subwavelength resonant grating filter placed directly in front of a semiconductor laser gain chip. The filter acts as a tunable wavelength-selective mirror. As the applied voltage to the filter changes from 0 to 22 V, the laser wavelength demonstrate...

The authors present a technique for the replication of molds for nanoimprint lithography (NIL) without solvents or etching. A thin hard amorphous silicon film is deposited onto imprinted or self-assembled polymer nanostructures by room-temperature conformal plasma-enhanced chemical vapor deposition. After attachment to another substrate and separat...

For the first time, a wafer-scale metal grid UV filter is fabricated by nanoimprint lithography and demonstrates cut-off wavelength of 350nm, peak transmission of 27% at 285nm and rejection ratio of 20dB at visible wavelength.

The advantages of integrating semiconductor devices at more than one level (‘3D integration’) are now recognized. Key to achieving monolithic 3DICs is the ability to form single crystal semiconductor islands at the upper level without unduly heating the lower level structures. In prior work a surface relief grating of 3.8μm pitch in the substrate w...

The authors present a novel hyperfidelity fabrication method for microlens arrays. The method consists of the steps of a fabrication of a sacrificial master mold of a microlens array in a soft polymer by photolithography and thermal reflow, b conformal duplication of a daughter mold of complementary patterns in a hard material by dispensing an UV-c...

To optimize nanoimprint lithography (NIL), it is essential to be able to characterize and control the NIL process in situ and in real time. Recently we have developed a real-time imprint monitoring by the scattering-of-light (RIMS) approach, which allows us to detect the degree of resist deformation and the duration of resist penetration by a mould...

We report an experimental and theoretical study of two most critical yet still to-be-answered issues in dispensing-based nanoimprint lithography (D-NIL): air bubble formation and absorption, and discuss their impact on NIL yield and throughput. Using real-time observation via video, we found two different mechanisms for air bubble formation (featur...

Surface relief formed by nanoimprinting and etching into a thermally grown SiO2 layer on Si was used to position the initial nuclei formed by chemically vapor deposited Si and Ge. By controlling the deposition conditions, the surface diffusion length was adjusted to be comparable to or larger than the spacing between features, thus favoring nucleat...

Imprint pressure uniformity is crucial to the pattern uniformity and yield of nanoimprint lithography (NIL) and, hence, its applications. We studied a novel imprint method, air cushion press (ACP), in which the mold and substrate are pressed against each other by gas pressure rather than solid plates, and compared it with a common method, solid par...

Accurate multi-level overlay capability for nanoimprint lithography (NIL) is essential to integrated circuit manufacturing and other multilayer imprint applications. Using the "beat" grating image (Moiré fringe) generated by overlaying two sets of gratings that have slightly different periods, we obtained an alignment signal with a sensitivity bett...

We show the fractionation of whole blood components and isolation of blood plasma with no dilution by using a continuous-flow deterministic array that separates blood components by their hydrodynamic size, independent of their mass. We use the technology we developed of deterministic arrays which separate white blood cells, red blood cells, and pla...

Alkylsiloxane self-assembled monolayers (SAMs) were formed on surface relief created by nanoimprinting and etching recesses into Si and SiO2. Rather than exhibiting the isolated domains seen on unpatterned surfaces after limited formation time, the SAM on nanoimprinted surfaces became continuous and uniform after only a short ( ∼ 5–10 min) reaction...

In this paper, we demonstrate spectrum narrowing and wavelength stabilization (both thermal and temporal) with a subwavelength resonant grating (SRG) for a single broad area laser (BAL) emitter running at moderate pump current. Our method is simple, low cost and easy to implement. A narrower spectrum width and much higher stability could be achieve...

Elastically stretchable metal interconnects are required for electronic skin. To date, the resistance of such thin-film interconnects has been found to increase much more with mechanical strain than expected from purely geometrical deformation of the conductor. It has been discovered that the resistance change due to fully elastic deformation is mi...

Using a real time imprint monitoring system (RIMS), the authors measured the process time for laser assisted nanoimprint lithography to be about 200 ns. They found that during this short period of time, the mold had been fully pressed into the resist, resulting in a full pattern transfer with high fidelity. Their results also demonstrated the capab...

A new technique for filling narrow and high-aspect ratio nanoscale via holes by laser-assisted direct imprint has been proposed and developed. In the process, the filling material (e.g., metals or Si) is first deposited onto the nano-via holes by a deposition method that has a poor step coverage and hence fills the holes partially with voids. Then...

Nanotechnology has the potential to revolutionize biology by making possible the construction of chip-based devices with nanoscale features that can not only detect and separate single DNA molecules by size but also--it is hoped in the future--actually sequence at the single molecule level. Understanding the physics of nanoconfined DNA is important...

One of the key problems in microfabrication and especially nanofabrication applied to biology is materials selection. Proper materials must have mechanical stability and the ability to hermetically bond to other surfaces, yet not bind biological molecules. They must also be wettable by water and have good optical properties. In this article, we rev...

In this paper we proposed a novel overlay alignment method using two sets of identical photonic crystals (PhCs). In this method the reflection or transmission spectrum of the two overlaid photonic crystals is measured to help wafer tilt, yaw rotation, and translation aligning. The initial testing results with two 1D photonic crystals and analysis o...

This paper presents examples in SOEs and NIL. It shows how to change the optical function of SOEs by changing the geometries of the sub-wavelength feature, while keeping the materials the same (e.g. Si): changing from waveplates to filters (e.g. photonic crystals), antireflection surfaces, polarizers, beam splitters, and to lenses. It also shows th...

We demonstrate continuous flow bifurcation of nanoparticles using the principle of deterministic lateral displacement. Recently arrays of microfabricated posts, tilted relative to the fluid flow direction, were successfully used to separate DNA fragments [1], microbeads [1,2] and to fractionate whole blood [3,4]. We scale down this technique using...

A key issue in nanoimprint lithography (NIL) is determining the ultimate pitch resolution achievable for various pattern shapes and their critical dimensional control. To this end, we demonstrated the fabrication of 6 nm half-pitch gratings and 0.04 mu m(2) cell area SRAM metal interconnects with 20 nm line half-pitch in resist by NIL. The mould fo...

The successful design of nanofluidic devices for the manipulation of biopolymers requires an understanding of how the predictions of soft condensed matter physics scale with device dimensions. Here we present measurements of DNA extended in nanochannels and show that below a critical width roughly twice the persistence length there is a crossover i...

Both ultrafast thermal and photocurable nanoimprint lithography (NIL) are studied and high fidelity transfers of nanopatterns from molds to resists have been achieved. In ultrafast thermal NIL, we use a single excimer laser pulse to melt a NIL resist polymer and imprint it using a fused silica mold. The entire imprint process, from melting the poly...

We present and demonstrate a novel imprint method, electrostatic force-assisted nanoimprint lithography (EFAN), where a voltage applied between a mold and a substrate generates an electrostatic force that presses the mold into a resist on the substrate. We have successfully used EFAN to pattern nanostructures in a photocurable resist spin-coated on...

A variety of self-assembly patterns, e.g., concentric rings, rods, and pillars, in polymer thin film have been achieved by lithographically induced self-assembly (LISA) in this study. The variations of the LISA patterns are controlled by many operation factors, such as the choice of the polymers, mask topology, process temperatures, surface tension...

The electrohydrodynamic instability of a thin film of initially static viscoelastic polymer under a mask is studied via a linear analysis. The conducting polymer film is separated from the mask by air. Under a normal electrical field, the initially flat polymer film self-assembles into well organized micro scale patterns. The driving force for the...