Chemical Lithography Research Articles

Fabrication of Thermosensitive Polymer Nanopatterns through Chemical Lithography and Atom Transfer Radical Polymerization

Micro- and nanopatterns of thermosensitive poly(N-isopropylacrylamide) brush on gold substrate were prepared by using chemical lithography combined with surface-initiated atom transfer radical polymerization. Self-assembled monolayers of 4'-nitro-1, 1'-biphenyl-4-thiol were structured by chemical lithography which produced cross-linked 4'-amino-1,1'-biphenyl-4-thiol monolayer within a nitro-terminated matrix. The terminal amino groups in monolayers were bounded with the surface initiator bromoisobutyryl bromide. After polymerization, the smallest size can reach to 70-nm line width and dots. The thermosensitivity of poly(N-isopropylacrylamide) brushes is demonstrated by contact angle measurement and fluid atomic force microscopy. This fabrication approach allows creating spatially defined polymer patterns and provides a simple and versatile method to construct complex micro- and nanopatterned polymer brushes with spatial and topographic control in a single step.

Nanostructured Polymer Brushes

Nanopatterned polymer brushes with sub-50-nm resolution were prepared by a combination of electron-beam chemical lithography (EBCL) of self-assembled monolayers (SAMs) and surface-initiated photopolymerization (SIPP). As a further development of our previous work, selective EBCL was performed with a highly focused electron beam and not via a mask, to region-selectively convert a SAM of 4'-nitro-1,1'-biphenyl-4-thiol to defined areas of crosslinked 4'-amino-1,1'-biphenyl-4-thiol. These "written" structures were then used to prepare surface-bonded, asymmetric, azo initiator sites of 4'-azomethylmalonodinitrile-1,1'-biphenyl-4-thiol. In the presence of bulk styrene, SIPP amplified the primary structures of line widths from 500 to 10 nm to polystyrene structures of line widths 530 nm down to approximately 45 nm at a brush height of 10 or 7 nm, respectively, as measured by scanning electron microscopy and atomic force microscopy (AFM). The relative position of individual structures was within a tolerance of a few nanometers, as verified by AFM. At line-to-line spacings down to 50-70 nm, individual polymer brush structures are still observable. Below this threshold, neighboring structures merge due to chain overlap.

Fabrication of SnO2 Nano Patterns Using Surface Relief Grating

ABSTRACTNano- and micro-structured SnO2 has been widely utilized as gas sensors. These SnO2 based gas sensors are often made by chemical etching, vapor deposition or lithography. Here we report a facile and vacuum-free technique to fabricate large area one-dimensional periodic SnO2 nano arrays using surface relief grating created on azobenzene functionalized polymer thin films as template. Atomic force microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy characterizations confirmed the successful fabrication of SnO2 nano arrays. The fabricated SnO2 structure exhibited the same periodicity as the template with a width of a few hundred nanometers.

Chemical Grafting of Biphenyl Self-Assembled Monolayers on Ultrananocrystalline Diamond

We have investigated the formation of self-assembled monolayers (SAMs) of 4'-nitro-1,1-biphenyl-4-diazonium tetrafluoroborate (NBD) onto ultrananocrystalline diamond (UNCD) thin films. In contrast to the common approach to modify diamond and diamond-like substrates by electrografting, the SAM was formed from the saturated solution of NBD in acetonitrile by pure chemical grafting. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and near edge X-ray absorption fine structure spectroscopy (NEXAFS) have been used to verify the direct covalent attachment of the 4'-nitro-1,1-biphenyl (NB) SAM on the diamond substrate via stable C-C bonds and to estimate the monolayer packing density. The results confirm the presence of a very stable, homogeneous and dense monolayer. Additionally, the terminal nitro group of the NB SAM can be readily converted into an amino group by X-ray irradiation as well as electrochemistry. This opens the possibility of in situ electrochemical modification as well as the creation of chemical patterns (chemical lithography) in the SAM on UNCD substrates and enables a variety of consecutive chemical functionalization for sensing and molecular electronics applications.

Ultrafine luminescent structures through nanoparticle self-assembly

We report the fabrication of ultrafine structures consisting of regular arrays ofnanoemitters through the self-assembly of luminescent nanoparticles on asilicon wafer. Nanoparticles of yttrium aluminium garnet (YAG) doped withEu3+ ions were synthesized by a sonochemical technique. These particles, suspended inethanol, are introduced onto a pre-patterned silicon wafer, covered with a thin oxidelayer. On annealing the sample in an ultrahigh-vacuum chamber, the nanoparticlesself-assemble along the pattern. We demonstrate this ‘chemical lithography’ byassembling the nanoparticles along a variety of patterns. We believe that suchself-organized nanopatterning of functional structures is important for the realization ofnanodevices.

Nanochemistry: a chemical approach to nanomaterials

Preface - In the Beginning there was Nano Nanochemistry Basics Chemical Patterning and Lithography Layer-By-Layer Self-Assembly Nanocontact Printing and Writing Nanorod, Nanotube, Nanowire Self-Assembly Nanocluster Self-Assembly Microspheres - Colours from the Beaker Microporous and Mesoporous Materials Self-Assembling Block Copolymers Biomaterials and Bioinspiration Self-Assembly of Large Building Blocks Nano and Beyond Nanochemistry and Nanolabs Subject Index

Self-Assembled Molecular Pattern by Chemical Lithography and Interfacial Chemical Reactions

The fabrication of lipid-modified molecular patterns by Chemical Lithography combined with interfacial chemical reactions is reported. In this method, self-assembled monolayers (SAMs) of 4'-nitro-1,1'-biphenyl-4-thiol (NBT) were structured by Chemical Lithography which produced cross-linked 4'-amino-1,1'-biphenyl-4-thiol (cABT) monolayers within a nitro-terminated (NBT) matrix. The terminal amino groups in the cABT monolayer were diazotized to create diazo cations, and the lipid monolayer with negative charge was assembled on the diazo regions by electrostatic attraction. Under the exposure of UV light, the photoreaction occurs. The diazonium groups interacting with the lipid headgroups via electrostatic attraction decompose and release N2 which leads to the lipid monolayer covalently attaching to the cABT region. The presence of phosphorus in X-ray photoelectron spectra (XPS) reveals the binding of the phospholipid layer to the cABT surface. Atomic force microscopy (AFM) images display that lipid-modified molecular patterns with different sizes and shapes and with a thickness of ca. 2.5 nm have been formed. The resulting lipid-modified molecular patterns are considered to be a first step towards obtaining stable biointerfacing patterns and studying biomolecular recognition.

Chemical lithography

Chemical lithography

Photolithographic Patterning of a Conductive Polymer Using a Polymeric Photoacid Generator and a Traceless Removable Group

AbstractSummary: In the present communication we describe a photolithographic method to produce polyaniline (PANI) patterns using PANI modified with a traceless removable functional group (nitrosated polyaniline, PANI‐NO) and external inexpensive polymeric photoacid generators (poly(vinyl chloride), PVC). Therefore, residual sub‐products created by irradiation of the plate do not remain occluded in the polymeric films. The borders of the patterns are better defined than in the case of chemical lithography using inorganic acids as the hydrolyzing agent. magnified image

Surface Modification with Orthogonal Photosensitive Silanes for Sequential Chemical Lithography and Site‐Selective Particle Deposition

Surface Modification with Orthogonal Photosensitive Silanes for Sequential Chemical Lithography and Site‐Selective Particle Deposition

Integrated Lithographic Membranes and Surface Adhesion Chemistry for Three-Dimensional Cellular Stimulation

The complex spatiotemporal organization of cellular and molecular interactions dictates the physiological function of cells. These behaviors are indications of an integrated response to a three-dimensional cellular environment and anchored in cell adhesion on scaffolds. Here, we are able to control interconnected structural, mechanical, and chemical stimuli by dictating the cellular environment through chemical surface modifications, soft lithography, and mechanical deformation. Control of these variables is obtained through the use of an elastomeric membrane chemically modified for cell adhesion with a pressure-driven cell-stretching device which creates a pattern of forces similar to those encountered in physiological environments. Further, the integration of lithographic methods and chemical patterning allows the introduction of space- and time-dependent parameters by combining mechanical stimulation, biochemical regulation, and scaffolding design. The method is applied to stimulate single cells and cell populations to examine cellular response with spatiotemporal control. This research provides the capacity to probe biological patterns and tissue formation under the influence of mechanical stress.

Generation of Amino-Terminated Surfaces by Chemical Lithography Using Atomic Force Microscopy

Self-assembled monolayers (SAMs) covered with nitroso end groups were reduced using an atomic force microscope. As the bias voltage become more negative (beyond -4 V), the surface potential of the scanned area become closer to that of the amino-terminated SAM. Following this chemical change, however, no change in topographic features was detected, implying retained stability of the underlying SAM layer. We then released carboxylate-modified polystyrene (PS) spheres into a pH 4 solution containing the sample. Subsequent imaging with atomic force microscopy (AFM) revealed that these PS spheres were only selectively immobilized on the regions that were originally scanned at -6 V to form amino termination. In summary, using AFM set to a specific voltage, we were able to selectively generate micropatterned regions of the SAM with amino termination.

Electron-beam lithography with aromatic self-assembled monolayers on silicon surfaces

Aromatic self-assembled monolayers are formed via the coupling of hydroxy head groups to hydrogen-terminated silicon surfaces. We first investigate the application of 4-hydroxy-1,1′-biphenyl as an ultrathin negative tone electron-beam (e-beam) resist using conventional e-beam lithography with a beam energy of 3 keV. We demonstrate the fabrication of nanometer silicon patterns that are transferred using the modified monolayer as a resist mask for a wet chemical etching process in potassium hydroxide. The necessary dose for complete cross linking was determined to be 20 mC/cm2. Using this approach, isolated silicon structures with lateral dimensions down to ∼10 nm and periodic structures with a resolution of ∼20 nm were fabricated. On the other hand, 4′-nitro-4-hydroxy-1,1′-biphenyl has been found not to form monolayers suitable for chemical lithography on hydrogenated silicon surfaces. Upon adsorption, the nitro groups are partially reduced to amino groups by the hydrogenated surface and some of the molecules bind to the surface via the nitrogen terminus.

Novel selective process via self-assembled monolayers for pattern growth of carbon nanotubes

In this study, a novel IC compatible deposition process to fabricate the CNTs pattern with tunable tube number density was successfully developed by using the liquid chemical technologies of self-assembled monolayers (SAMs) and the Fe-assisted CNTs growth. The tube number density could be controlled by changing the SAMs formation and post processing parameters. The Si wafers with the a:Si/Si 3N 4 layer patterns were first prepared by low pressure chemical vapor deposition (LPCVD) and lithography techniques to act as the substrates for selective deposition of SAMs. The selectivity of SAMs from APTMS solution ( N-(2-aminoethyl)-3-aminopropyltrimethoxsilane) is based on its greater reactivity of head group on a:Si than Si 3N 4 films. The areas of pattern with SAMs will first chelate the Fe 3+ ions by their diamine-terminated group. The Fe 3+ ions were then consolidated to become Fe-hydroxides in NaBH 4 solution to form the Fe-hydroxides pattern. Finally, the Fe-hydroxides pattern was pretreated in H plasma, and followed by CNTs deposition using Fe as catalyst in a microwave plasma-chemical vapor deposition (MPCVD) system to become the CNTs pattern. The products in each processing step, including SAMs, Fe-hydroxides and CNTs, were characterized by contact angle measurements, scanning electron microscopy (SEM), Raman, XPS and Auger spectroscopy. The results show that the main process parameters include the surface activation process and its atmosphere, consolidation time and temperature, H plasma pretreatment. The function of each processing step will be discussed.

Chemical Lithography by Surface-Induced Photoreaction Of Nitro Compounds

Searching for systems of self-assembled monolayers (SAMs) that can be used as templates for chemical lithography, we found that nitro groups on aromatic SAMs are selectively converted on Ag to amino groups by irradiation with a visible laser. 4-nitrobenzenethiol on Ag was thus converted to 4-aminobenzenethiol by irradiating it with an Ar + laser. This was evident from surface-enhanced Raman scattering (SERS) as well as from a coupling reaction forming amide bonds. The surface-induced photoreaction allowed us to prepare patterned binary monolayers on Ag that showed different chemical reactivities. Using the binary monolayers as a lithographic template, we induced site-specific chemical reactions, such as the selective growth of biominerals on either the nitro- or amine-terminated regions by adjusting the crystal-growth conditions. We also demonstrated that patterned, amine-terminated monolayers can be fabricated even on gold by using silver nanoparticles as photoreducing catalysts.

Chemical lithography of a conductive polymer using a traceless removable group.

Polyaniline could be easily converted into nitrosated polyaniline by reaction with nitrite ion in acids. The product is soluble in common solvents and could be deposited into thin films. The nitrosated polyaniline could be back-converted into polyaniline by acid hydrolysis. On the basis of those properties, a simple chemical lithographic process to produce conductive polyaniline images is demonstrated.

Surface-initiated polymerization on self-assembled monolayers: amplification of patterns on the micrometer and nanometer scale.

Patterned polymer brushes can be produced on the micrometer and nanometer scale by a combination of self-assembly and lithography. Self-assembled monolayers of biphenyl thiols were structured by chemical lithography. The patterns were amplified by surface-initiated polymerization.

Modular overconstrained weak-link mechanism for ultraprecision motion control

We have designed and constructed a novel miniature overconstrained weak-link mechanism that will allow positioning of two crystals with better than 50 nrad angular resolution and nanometer linear driving sensitivity. The precision and stability of this structure allow the user to align or adjust an assembly of crystals to achieve the same performance as does a single channel-cut crystal, so we call it an “artificial channel-cut crystal.” Unlike the traditional kinematic linear spring mechanisms, the overconstrained weak-link mechanism provides much higher structure stiffness and stability. Using a laminar structure configured and manufactured by chemical etching and lithography techniques, we are able to design and build a planar-shape, high stiffness, high precision weak-link mechanism. In this paper, we present recent developments for the overconstrained weak-link mechanism. Applications of this new technique to synchrotron radiation instrumentation are also discussed.

Nanoscale Site-Selective Catalysis of Surface Assemblies by Palladium-Coated Atomic Force Microscopy Tips: Chemical Lithography without Electrical Current

Chemical reactions of terminal functional groups of organosiloxane surface assemblies were induced by a catalytically active palladium-coated atomic force microscopy (AFM) tip, resulting in lithographed patterns with minimum measured line widths of 33 nm. We describe three schemes: Pd-catalyzed transfer hydrogenation on terminal azide and carbamate (CBZ-amino) functional groups and Pd-catalyzed addition of aminobutyldimethylsilane on the terminal alkene bond of N-octenyldimethylsiloxane surface assemblies. The minimum applied force required to cause chemical change in the end functional groups is approximately 2.5 μN, and detectable amounts of chemical conversion occurred at raster scan rates up to 5 μm/s. Physical dislocation of the surface assembly competes with chemical writing, but this can be alleviated by strong covalent attachment of the surface assembly to substrate (i.e., by complete condensation of assembling silanols to siloxane bridges). For the strongest trialkoxysilane-derived surface assemblies, virtually complete physical dislocation of the surface assembly occurs at 7.6 μN. Each chemical writing scheme described in this paper results in terminal amine functional groups which are labeled with fluorescent probes. Features are imaged with confocal and atomic force microscopy. Labeling via covalent attachment of biotin, followed by attachment of streptavidin-coated gold nanoparticles, also gave evidence of chemical conversion.

Generation of Surface Amino Groups on Aromatic Self-Assembled Monolayers by Low Energy Electron Beams—A First Step Towards Chemical Lithography

Generation of Surface Amino Groups on Aromatic Self-Assembled Monolayers by Low Energy Electron Beams—A First Step Towards Chemical Lithography