Nanolines as small as 7 nm wide have been formed using a small-aggregate resist and supercritical resist drying. Aggregates consisting of resist polymers cause pattern roughness and cause nanolines to break. Hydrogen silsesquioxane (HSQ) is a resist material in which the aggregates are small due to its three-dimensional network. Development with an aqueous solution of TMAH provides high-contrast patterns. The problem that nanolines formed in HSQ collapse after development is solved by a supercritical resist drying technique. Supercritical drying suppresses the swelling of the resist by the rinse solution during development and thereby prevents nanolines from collapsing. The use of both small-aggregate HSQ resist and supercritical resist drying enables free-standing nanolines with a high aspect ratio to be formed without collapse.

The charge transport and quantum interference effects in low-dimensional mesoscopic carbon networks prepared using self-assembling were investigated. The mechanism of conduction in low-dimensional carbon networks was found to depend on the annealing temperature of the nitrocellulose precursor. The charge transport mechanism for carbon networks obtained at Tann=750 0C was found to be the hopping conductivity in the entire investigated temperature range. The Coulomb gap near the Fermi level in the density of states was observed in the investigated carbon networks. The width of the Coulomb gap was found to be decreased with the annealing temperature of the carbon structures. The crossover from the strong localization to the weak localization regime of the charge transport in the carbon structures, obtained at Tann=950 0C and Tann=1150 0C, was observed in the temperature range T>100 K and T>20 K, respectively.

By blending 3-aminopropyl-siloxane oligomers (pAPS) with chitosan (CHI) self-assembled hybrid films have been obtained. The influence of the incorporation of LiClO4 on the morphology of these transparent and flexible hybrid films has been studied. It was found that when this salt is added in amounts slightly over the limit of the maximal homogeneous incorporation a process of anisotropical crystallization begins. For a hybrid with composition CHI/pAPS/LiClO4 = 0.6/1/0.8M, Video-Enhanced Differential Interference Contrast microscopy (VEC-DIC) of the first three layers of the films showed that each layer have oriented patterns with angles of exactly 60 degrees between the planes. These results in combination with FTIR analysis of the products indicate that lithium ions behave as strong structure directing agent. This system can be considered as a biomimetic model for biomineralization processes. An interaction scheme comprising the components of this hybrid system is proposed.

The ability to self-assemble nanoparticles into thin films and subsequently characterize the structural or morphological responses to interfacial chemical/biological reactivity is increasingly important. Surface patterning and tailoring us ing nanoparticle assemblies are expected to provide such abilities for selective immobilization and chemical and biological recognition. We describe herein recent results of an investigation of hydrogen-bonding based self-assembly of core-shell nanoparticles onto monolayer-patterned surfaces, and its potential utility for in-situ atomic force microscopic characterizations of interfacial chemical and biological reactivities. This system is potentially useful for immunoassays based on topographical height changes with well-defined internal morphological standard.

Simulations have been performed to study the effects of different masking materials (Cr, Au, W and Si) on near field optical contact lithography. For near field amplitude masks it is found that Cr is an excellent material at blue/UV wavelengths, due to its small skin depth. Au is too transmissive to be considered. W has a small skin depth like Cr, although its dielectric behaviour at blue/UV wavelengths leads to image reversal phenomena that may be undesirable. Image reversal is even more pronounced for Si. For Evanescent Interferometric Lithography (EIL) - a technique that relies on surface-plasmon-induced resonant enhancement of the evanescent fields beneath a grating - Cr and W are again superior to Au, and significant intensity enhancements are predicted beyond the grating cutoff. For Si the resonant enhancements can be very large and narrow band, which may be of great advantage. For example, near field exposure intensity approximately 100 times the incident intensity is predicted for a 270 nm period silicon grating illuminated at a wavelength less than 10 percent higher than cutoff.

A process to fabricate a periodic surface structure at biologically important length scale is developed and nanostructured silicon surface with a periodicity of 38 nm has been obtained. The technique relies on controlled etching of a dislocation array in the twist boundaries formed by silicon bicrystals. The deviation from a perfect periodic structure and the method to improve the perfection have been investigated.

Currently, the microlithography industry creates large amounts of organic and aqueous wastes in the production of semiconductors. Using carbon dioxide can possibly eliminate the majority of these waste solvents as well as eliminate the image collapse problems shown with aqueous base development. We will discuss the use of carbon dioxide to replace the most solvent intensive steps of the microlithography process, spin coating, developing, and stripping. However, before CO2 can replace conventional solvents, photoresist systems must be designed and synthesized to be compatible with CO2. These photoresist systems must be soluble in liquid CO2 to insure that thin-uniform coatings can be produced by spin coating while maintaining characteristics of conventional resist systems such as low absorbance, high sensitivity, solubility contrast, good resolution, and etch resistance. Using our CO2compatible resist system, we will demonstrate the ability of CO2 to spin coat uniform thin-films which (after exposing and PEB) can be developed using scCO2 to produce lithography features that may be stripped in CO2. Thus, revealing the enormous potential of CO2 to provide the microlithography industry an opportunity to escape its water and organic solvent dependence as it moves toward 157nm lithography.

A photoacid generating (PAG) sulfonium monomer was designed and synthesized. CA resists were prepared based on this PAG monomer. Incorporation of the PAG in the resist backbone offered a few advantages such as high sensitivity and absence of phase separation. These resists proved to be especially useful for low-voltage EB lithography.

We describe a method for patterning substrates with colloidal particles in any designed two-dimensional structure. By using optical tweezers particles are brought from a reservoir to a surface that carries a surface charge opposite to that of the particles. Using this technique large, two-dimensional patterns can be created, where the pattern can be manipulated on a single particle level. We show that these structures can be dried using critical point drying thus preventing distortions due to surface tension forces. After drying patterned surfaces can be used for further processing, which includes repeating the procedure of patterning. We show some first results of three-dimensional structures created using this layer-by-layer method. The method is generally applicable and has been demonstrated for a variety of (core-shell) colloidal particles including particles that are interesting for photonic applications like high-refractive index (ZnS)-core – silica shell particles, metallodielectric (gold)-core – silica-shell particles, fluorescently labeled particles and small (several nanometers large) gold particles. Particle sizes used range from a few nanometers to several micrometers.

Large scale periodic arrays of Co/Pt multilayer dots with perpendicular magnetic anisotropy are fabricated utilizing optical interference lithography with Ar+ ion lasers operating at wavelengths of 457nm and 244nm, respectively. The experimental technique allows us to fabricate dot-arrays with periodicities ranging between 125nm and 1100nm and with corresponding dot diameters between 70nm and 740nm. The dot-arrays are prepared on (100)-silicon substrates covering a total area of up to 20cm2 with a maximum dot density of about 4.1x1010dots/in2 as well as within the surface of (110)-silicon substrates. The global magnetic properties of the dot-arrays are characterized by the magneto-optical Kerr effect. The micromagnetic properties of a single Co/Pt dot are measured with quantitative magnetic force microscopy (QMFM) by using a MFM-tip, the magnetic properties of which have been calibrated within the point probe approximation with nanofabricated current carrying rings. This allows us to measure quantitatively the z-component of both the magnetization and the stray field of a Co/Pt dot on the nanometer scale.

Extreme Ultraviolet (EUV) lithography is gaining momentum as the patterning technology of choice for the semiconductor nodes with less than 70-nm half-pitch. As such, it must be ready for manufacturing in the 2006-2007 time frame, and it must be extendable to the lower limits of CMOS technology. Successful patterning of 40-nm dense lines in viable EUV photoresists indicates that today's resist materials may have the necessary resolution, but better optics are needed to verify this more rigorously. Although little is understood about the impact of line-edge roughness (LER) on device performance, it is generally assumed that EUV LER must be less than 3 nm 3σ. EUV lines have been printed with LER as low as 4 nm 3σ, but they were printed with unacceptable photospeed. Deliberate attempts to increase the photospeed while maintaining low LER have produced a resist with sizing dose of 1.7 mJ/cm2 and LER of 6.6 nm 3σ. Photospeed is important because EUV photons are difficult to create, and the photoresist must use them efficiently for economically acceptable throughput. Throughput models indicate that patterning doses may need to be 1-2 mJ/cm2, and only 30-40% of these photons will be absorbed, so the resists must be able to accommodate statistical dose fluctuations that are an appreciable fraction of the mean dose. Highly sensitive resists such as these have been produced with good LER. Since all resist materials absorb EUV radiation strongly, the photoresist layer will have to be less than 150 nm thick. Resists this thin pose problems for device manufacturing, largely because they will not have acceptable etch resistance, and this etch resistance will have to be recovered in some other way. Efforts have begun to integrate hard masks with thin resists in real device fabrication. Defect data indicate that defect densities do not increase in resist films less than 100 nm thick, and transistors, via chains, and microprocessors have all been fabricated with these thin-resist/hard-mask integrations.

A conventional ion mill used for thinning transmission electron microscope samples has been used to produce nanoscale surface corrugations on the thermal oxide of Si. Using Ar ions with energies from 1.1 to 2.5 keV in an off-normal incidence geometry, the corrugations were produced with wavelengths from 30 to 80 nm and amplitudes of ~1 to 2 nm. The corrugated pattern in the oxide has been transferred to the underlying Si substrate by reactive ion etching, producing structures that have a much higher aspect ratio than the original corrugations.

We present a method for fabricating polymer brushes with a gradual variation of grafting density on solid substrates. The technique for generating such structures consists of: i) deposition of a molecular gradient of polymerization initiator on the solid substrate, and ii) polymerization from the substrate bound initiator centers (“grafting from”). In this publication we describe the preparation of gradient polymer brushes of poly(acryl amide) on silica-covered substrates. We show that the polymer density within the gradient polymer brush can be varied by controlling the polymerization time.

The preparation of monodisperse Fe nanoparticles and self-assembly into hcp and fcc or fcc-like arrays is described. Here dipolar interactions dominate for the interparticle spacings studied (1.4-3.4 nm). Comparison of the low temperature magnetic properties of multilayer arrays with those of dilute suspensions of the same particles show increased coercivity and slower magnetic relaxation in the arrays. Mean field calculations of magnetic interaction fields suggest the type of ordered structures formed.

Highly ordered alumina pore channel arrays are used as templates for the fabrication of magnetic nanowire arrays. These well-defined templates are based on the approach by Masuda and Fukuda and have an interpore distance of 65 and 100 nm and a monodisperse pore diameter of ≍30 nm. The pore channels are hexagonally arranged in 2D-domains, which extend over more than ten interpore distances. Nearly 100% metal filling of the alumina pore structures is obtained by a novel pulsed electrodeposition technique. Due to the high ordering degree of the nanowires arrays, we detect a squareness of ≍100% and coercive fields of 1200 Oe in the direction of the nanowires. The MFM measurements have been carried out by applying magnetic fields on magnetized and demagnetized samples to study the switching behavior of individual nanowires inside the arrays. Magnetic wires have been locally switched by a strong MFM tip and a variable external magnetic field. The MFM results show a good agreement with the bulk magnetic hysteresis loops.

In this paper, molecular compounds that come from the class of tungsten or molybdenum polyoxometallates (POM) are examined as components of polymeric materials with potential use in nanolithography and molecular devices. In the past, POMs have been used as components of DUV resists with promising results, but the metallic compound presence and their unconventional processing demands discouraged their further use in microlithography. In this paper routes for the use of these compounds in e-beam nanolithography are investigated. Different resist formulations, where poly (vinyl alcohol) and poly (methyl methacrylate) are used as host polymers, will be discussed along with the related process issues.

First results from the use of polyoxometallate compounds as active elements, or components, of molecular electronic nanodevices will be also presented. The electronic transport properties of the composite materials have been tested using planar devices with contact distances of 40μm, 5μm, 50nm and 25nm. Contacts were fabricated using electron beam lithography and a lift–off process. Even at room temperature conditions conductivity peaks appear in the case of distances smaller than 25nm. These peaks are related to the energy distance of the HOMO – LUMO levels of the active molecules and the work function of the electrode used. The position and the size of the peaks depend upon the mean distance of the molecules as well as the electrode distance. On the other hand when the contact is illuminated, conductivity increases even by two orders of magnitude. This is attributed to the photon excitation of electrons from the HOMO.

The characteristics of TNT (trinitrotoluene) crystals in Composition B have been studied using atomic force microscopy (AFM). The size of TNT crystals has been examined by analyzing the surface structure that is exhibited after mechanical failure of the Composition B. The mechanical failure occurs when the material is subjected to high acceleration (high g)inan ultracentrifuge and. the shear or tensile strength is exceeded. AFM examination of the topography of the Composition B fracture surface reveals fracture across columnar grains of the TNT. The width of the columnar TNT grains ranges in size from ~ 1 μm to~2 μm. Their height ranges in size from ~ 50 nm to ~ 300 nm.

The application of a microscopic surface texture produced by ion beam sputter texturing to the surfaces of polymer implants has been shown to result in significant increases in cellular attachment compared to smooth surface implants in animal studies. A collaborative program between NASA Glenn Research Center and the Cleveland Clinic Foundation has been established to evaluate the potential for improving osteoblast attachment to surfaces that have been microscopically roughened by atomic oxygen texturing. The range of surface textures that is feasible depends upon both the texturing process and the duration of treatment. To determine whether surface texture saturates or continues to increase with treatment duration, an effort was conducted to examine the development of surface textures produced by various physical and chemical erosion processes. Both experimental tests and computational modeling were performed to explore the growth of surface texture with treatment time. Surface texturing by means of abrasive grit blasting of glass, stainless steel and polymethylmethacrylate surfaces was examined to measure the growth in roughness with grit blasting duration by surface profilometry measurements. Laboratory tests and computational modeling was also conducted to examine the development of texture on Aclar® (chlorotrifluoroethylene) and Kapton® polyimide, respectively. For the atomic oxygen texturing tests of Aclar®, atomic force microscopy was used to measure the development of texture with atomic oxygen fluence. The results of all the testing and computational modeling support the premise that development of surface roughness obeys Poisson statistics. The results indicate that surface roughness does not saturate but increases as the square root of the treatment time.

This paper will discuss aspects of resist properties required for nanolithography using high-energy electrons. A comprehensive image formation model is presented for positive and negative chemically amplified resists where most aspects have been considered (from exposure through development) for e-beam nanolithography (EPL, DWL). A series of optimization studies are performed using the modulation of soluble site density after PEB as a metric to characterize resist imaging performance. Base loading, blocking fraction and acid diffusion properties are investigated. Slower acid diffusion near regions with deprotected sites dominates during PEB and contributes to a sharp image modulation. Electron beam exposed nanostructures exhibit spatial fluctuations of soluble sites in the material left after development, which may alter etch resistance and pattern collapse. Soluble site fluctuations arise from the low statistics involved in the image formation and are significant contributors to the sidewall roughness.

We report on a non-lithographic method for the preparation of self-assembled FePt nanoparticles via inert-gas condensation. Prior to deposition the particles can be sintered in flight at temperatures as high as TS = 1273 K. Whereas un-sintered particles have irregular shapes, particles sintered at elevated temperatures TS ≥ 793 K show a regular faceting. (High resolution) transmission electron microscopy ((HR)TEM) shows that these regularly faceted particles are of icosahedral structure. When being deposited onto amorphous carbon films, the gas-phase sintered particles are found to have a high mobility. In particular, for the high-temperature sintered FePt nanoparticles, we observe that this mobility leads to the formation of particle arrays with hexagonal close-packed arrangements. Within these ordered patches, the particles are separated from one another. Analytical investigations using energy filtered TEM (EFTEM) show that a carbon layer is formed between the particles. Magnetization analyses give results showing that the gas-phase sintered particles are superparamagnetic at room temperature with a blocking temperature of TB = 49K.