Recently, the development of a versatile thermochemical nanolithography (TCNL) technique has been reported. It allows simultaneous control of the local chemistry and topography of thin polymer films. This technique can pattern sub 15 nm chemical and topographical features at the rate of 1.4 mm per second by inducing thermally-activated chemical reactions by means of a heated atomic force microscope (AFM) tip. TCNL is achievable in different environments and can easily be adapted to a variety of substrates and chemical functionalities. Here, we demonstrate that a thin polymer film can be chemically modified twice using TCNL to tune its wettability. We are able to write hydrophilic nanopatterns over a hydrophobic polymer surface upon a first step heating and then revert back to hydrophobic surface by a second step heating. This write-read-overwrite capability is particularly useful in data storage application and complex nanofluidic device design.

A method to grow arrays of multibranched carbon nanostructures is explained. We use the electron-beam-induced deposition method using a transmission electron microscope with ∼10−6 Torr vacuum where hydrocarbons are present in the chamber. Saw-tooth nano-patterns were made with a focused ion beam in porous silicon substrates. Due to the dielectric properties of the films the patterns provide the corresponding sites in which high local electric fields appear during irradiation thus allowing the hydrocarbons to become preferentially attracted to those active sites. We found that the adequate ion dose to create well defined saw-tooth nano-patterns was between 8 and 10 nC/μ2 at 30 kv. Electron energy-loss spectroscopy on the branched carbon nanostructures show a high concentration of sp2 sites suggesting that they are made of graphite-like amorphous carbon.

There are a range of applications for bicontinuous metal micro and nanostructures including as porous electrodes for supercapacitors, in fuel cells and in advanced batteries. We have previously demonstrated a number of methods of generating metal nanostructures by electrodeposition into various templates including hexagonal surfactant phases and mesoporous silica. More recently we have been exploring the application of oil-in-water microemulsions as templates. We have found empirically that the formation of microstructure is strongly effected by the viscosity of the oil phase, the rate of metal electroreduction and the surface roughness of the substrate. We interpret these observations as reflecting a competition between growth of the metal around the oil droplet and the redistribution of the oil in front of the growing metal film. We are currently exploring bicontinuous and water-in-oil phases with the expectation that such templates will yield bicontinuous metal films with larger accessible surface areas. Preliminary results with water-in-oil phases appear to show the formation of bicontinuous nanostructured films on the 20 nm length scale.

Although the phase fractions in dual phase systems are often compared with the percolation threshold for a randomly-assembled composite, most two-phase systems are non-random by virtue of correlations introduced during processing or as a consequence of microstructural evolution. This study examines the two dimensional percolation threshold in systems with soft impingement, i.e., when the phase distribution is affected by diffusional interactions between growing second phase particles. Phase field modeling is used to simulate the nucleation and growth process, with many simulations conducted at various system sizes and equilibrium phase fractions to obtain percolation probabilities. The value of the percolation threshold in the thermodynamic limit is estimated based on the finite size scaling behavior of the system. The value of the critical exponent ν (the size scaling exponent) is also estimated.

Periodic arrays of nano-sized Si and Ni dots were fabricated by only irradiating a linearly polarized Nd:YAG pulsed laser beam to Si and Ni thin films deposited on silicon dioxide (SiO2) film. The interference between an incident beam and a scattered surface wave leads to the spatial periodicity of beam energy density distribution on the surface of the irradiated samples. A thin film was melted using a laser beam, and the molten film was split and condensed owing to its surface tensile according to the periodic energy density distribution. Then, the fine lines (line and space structure) were formed periodically. After the formation of fine lines, the sample was rotated by 90°, and the laser beam was irradiated. The periodic energy density distribution was generated on the fine lines, and the lines split and condensed according to the periodic energy density distribution. Eventually, the periodically aligned nano-sized dots were fabricated on the SiO2 film.

Despite their large lattice mismatch of 18 %, the lattices of Bi(111) and Si(001) fit surprisingly well. A remaining compressive strain in the Bi film of 2.3 % along the direction is accommodated by the formation of a periodic array of edge-type misfit dislocations confined to the interface. The strain fields surrounding each dislocation interact with each other, producing a quasi-periodic nanopattern of grating-like periodic height undulations on the surface. The separation and the amplitude of the height undulations have been derived by spot profile analyzing LEED and STM surface height profiles. The observed undulations agree well with elasticity theory.

This paper describes a new technique for fabrication of nano-sized taper structure formed by simple wet chemical etching using catalysis of gold (Au) nanoparticle. Single nano-sized Au particle dispersion solution was coated onto Si(111) substrate with polished surface. Then, the samples were soaked in an aqueous etching solution of hydrofluoric acid (HF) and hydrogen peroxide (H2O2). The surface of 15-min-etched Si substrate appeared black. The reflectivity of the Si substrate was reduced to below 5% throughout the entire spectrum from 300 to 800 nm owing to nano-sized taper structure called subwavelength structure (SWS). The fractional area occupied by Si as a function of the depth across the textured layer showed a smooth increase of density up to a depth. The observed optical effects are explained by the formation of a nanoscale taper structure, representing an effective medium with a smooth transition of the refractive index from that of air to that of Si.

During a typical chemical etching process growth front morphology generally generates an isotropic rough surface. In this work, we show that it is possible to form a rippled surface morphology through a geometrical self-assembly process using a chemical oblique angle etching technique. We observe in our Monte Carlo simulations that obliquely incident reactive species preferentially etch the hills that are exposed to the beam direction due to the shadowing effect. In addition, species with non-unity sticking (etching) coefficients can be re-emitted from the side walls of the hills and etch the valleys, which at the end can lead to the formation of ripples along the direction of the beam. This mechanism is quite different than the previously reported ripple formation during ion-beam bombarded surfaces where the particles have much higher energies, lower incidence angle and ripple formation is mainly due to physical deformation of the surface. We investigate the ripple formation process in our simulated surfaces for a wide range of etching angle and sticking coefficient values.

We have investigated the effect of the substrate-surface morphology on the growth of Al whiskers grown by high temperature glancing angle deposition (HT-GLAD). Before the HT-GLAD of Al at 390 °C, the morphology of the substrate was systematically modified by depositing nanocolumnar SiO2 layer of thickness between 0 and 100 nm on the flat SiO2 layer. Aluminum whiskers with the width of ≈100 nm and the length ≤ μm are found on all the samples. The number of short whiskers, which can be grown from very small nuclei, depends strongly on the thickness of the SiO2 nanocolumnar layer and shows the maximum at SiO2 thickness of 20 nm. On the other hand, the number of long whiskers, which requires extraordinary amount of Al than that deposited on the side surface of the whikers, is almost independent of SiO2 thickness. These facts suggest that the surface roughness of the substrate plays an important role in the nucleation of the whiskers and that there are some transport processes of Al, which are insensitive to the surface morphology.

The behavior of nano-scale liquid metal droplets has recently received renewed research interest following the exciting new observations of Sutter and Sutter [1]. In the present paper, we consider whether similar conditions can be generated for observing liquid metal droplet phenomena in a scanning probe architecture. Strong interactions between tip and sample in tunnelling microscopies can be deliberately invoked by lowering the tunnel gap impedance. Indeed, nanoscale features may be created this may, often exhibiting temporal stability suggestive of applications for ultra high density data storage. Alternatively, unstable features may form, and their decay characteristics can be related to local dynamics and kinetics. In real liquids, one such evolutionary mode involves the phenomenon of wetting, and the formation of thin precursor films. Here, it is demonstrated that a similar process may occur for the decay of a nanoscale mound of [presumed] Au atoms onto an Au(111) substrate. The mound is thought to be created by a ‘jump-to-contact’ process when the gap impedance, Zg, is deliberately lowered by reducing the tip-surface displacement. Resultant features have a diameter of circa 30nm, and heights of up to l0nm. They appear stable when scanned repeatedly at gap impedances higher than 10MΩ, however if Zg is lowered below 500kΩ, then morphology can alter dynamically, and a thin layer of material, only two atomic widths thick, is seen to emanate from the periphery. Relaxation in the nanostructure is observed. Interestingly, the observations agree qualitatively with wetting phenomena observed on microscale droplets of involatile liquids on solid surfaces. Favourable comparisons may also be drawn in the light of recent results using molecular-dynamics simulations and Monte-Carlo methods.

Nano- 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.

The violent interaction between pressure driven cavitation nuclei and nearby rigid substrates is usually a troublesome occurrence, giving rise to damage, and often system failure in hydraulic systems. However, the extreme nature of the phenomenon can also be exploited in situations where deliberate wear or erosion of a material is desireable, such as with the application of shock wave lithotripsy to fragment kidney stones in a medical context. The purpose of the present study was to examine whether a system can be designed so as to afford a level of control over cavitation processes, so that other useful applications might arise. Specifically, we looked at controlling single cavitation nuclei, constituted by encapsulated microbubbles, in proximity to a nearby rigid substrate and activated by ultrasound. This was achieved using a novel optical trapping arrangement, which facilitated establishment of an arbitrary, stable, initial spatial configuration for a bubble system. Critically, exercising optical control in such a way meant that a microbubble could be isolated from a resident population during insonation thus ensuring that ‘cross-talk’ with the rest of the bubble population was minimised. We observed, using high speed microphotography at circa one million frames per second that fine microjets are issued from cavitation microbubbles, and these impact the nearby surface, creating indentations of controllable size. Specific applications may arise that exploit this action, which, in the general case we refer to as ‘sonolithography’. However, scaling up the process to activate multiple bubbles at once, may lead to complications arising via the action of secondary radiation forces. We discuss the salient aspects of our preliminary findings on this subject herein.

In this work, thin layers of poly(methyl methacrylate) (PMMA) on Ni on silicon <111> substrates were etched almost completely away by oxygen RIE, leaving only the topmost portion of the roughness, generating nanodots of PMMA approximately 30-40nm or smaller in size. After sufficiently hard baking the samples to promote PMMA adhesion to the Ni and to increase the robustness of the PMMA, the nanodots were used as a mask to etch the thin Ni films, thus generating Ni nanodots on Si. The Ni nanodots were then used as a reactive ion (RIE) etch mask, thereby generating Si nanopillars. With further understanding of the mechanism of the generation of the roughness of the PMMA, or with the use of other polymeric materials suitable as wet etching masks, nanodots of varying size should be attainable. This method represents a very simple, low cost, scalable, and general technique to produce nanodots of various thin metals on various substrates.

A “hydrodynamic” model has been proposed to describe nanopattern formation and dynamics on amorphous surfaces eroded by ion-beam sputtering (IBS), that relates to descriptions of pattern formation in macroscopic systems such as aeolian sand dunes. At variance with previous continuum models of the morphology of ion-sputtered surfaces, the dynamics of the species that diffuse along the surface is coupled in a natural way to that of the surface height. We report recent results for this model, considering normal and oblique ion incidence, for both fixed and rotating targets, and include comparison to recent experiments on silicon. Effective interface equations can be obtained, that generalize the anisotropic Kuramoto-Sivashinshy equation through additional conserved Kardar-Parisi-Zhang type nonlinear terms. In general dot or ripple patterns form, that later evolve exhibiting complex nonlinear dynamics. Thus, we observe interrupted coarsening behavior such that, for normal incidence, domains of hexagonally ordered structures appear, that compare favorably with those obtained in many experiments of nanodot formation by IBS. In other parameter regions, this short-range ordered patterns coexist with long range disorder and kinetic roughening. For oblique incidence, a ripple pattern is generically obtained that also shows interrupted coarsening and other nonlinear features like non-uniform transverse motion, again reproducing experimental observations.

In this paper we develop a Brownian dynamics model applied to position metal nanoparticles from the gas phase onto electrostatic-patterns generated by biasing P-N junction substrates. Brownian motion and fluid convection of nanoparticles, as well as the interactions between the charged nanoparticles and the patterned substrate, including electrostatic force, image force and van der Waals force, are accounted for in the simulation. Using both experiment and simulation we have investigated the effects of the particle size, electric field intensity, and the convective flow on coverage selectivity. Coverage selectivity is most sensitive to electric field, which is controlled by the applied reverse bias voltage across the p-n junction. A non-dimensional analysis of the competition between the electrostatic and diffusion force is found to provide a means to collapse a wide range of process operating conditions and an effective indicator or process performance.

It was assumed in the past that aluminum is not a platform of choice for surface enhanced Raman scattering (SERS) experiments: this was in spite of its large negative permittivity value, larger than gold or silver at optical wavelength. It was also assumed that any oxide on top of metallic platform significantly hinders SERS signals. In addition, graphene has not been studied on perforated substrates. Here we use periodically perforated and oxidized aluminum surfaces to examine electrical and optical properties of multi layered graphene. Linear and nonlinear optical methods were used to characterize single and multi layered structures.

Film growth of organic semiconductor α-sexithiophene (6T) was studied using substrates with artificial periodic grooves. The grooves were fabricated on thermally oxidized silicon substrates by electron beam lithography. Based on the orientation analysis by atomic force microscopy and grazing-incidence x-ray diffraction, part of the 6T grains grew having the in-plane orientational relationship with the artificial grooves. This phenomenon corresponds to “ggraphoepitaxy” which has been well known in inorganic materials research field. As well as the in-plane preferred orientation, one-dimensional structure consisting of connected 6T grains was observed. The electrical conduction properties of the films were also evaluated.

Ion beams of sufficient energy to erode a surface can lead to surface modulations that depend on the ion beam, the material surface it impinges, and extrinsic parameters such as temperature and geometric boundary conditions. Focused Ion Beam technology both enables site-specific placement of these modulations and expedites research through fast, high dose and small efficient use of material. The DualBeam (FIB/SEM) enables in situ metrology, with movies observing ripple formation, wave motion, and the influence of line defects. Nanostructures (ripples of >400nm wavelength to dots spaced <40nm) naturally grow from atomically flat surfaces during erosion, however, a steady state size may or may not be achieved as a consequence of numerous controlled parameters: temperature, angle, energy, crystallography. Geometric factors, which can be easily invoked using a FIB, enable a controlled component of deposition (and/or redeposition) to occur during erosion, and conversely allow a component of etching to be incurred during (ion-beam assisted) deposition. High angles of ion beam inclination commonly lead to “rougher” surfaces, however, the extreme case of 90.0° etching enables deposition of organized structures 1000 times smaller than the aforementioned, video-recorded nanostructures. Orientation and position of these picostructures (naturally quantized by their atomic spacings) may be controlled by the same parameters as for nanostructures (e.g. ion inclination and imposed boundary conditions, which are flexibly regulated by FIB). Judicious control of angles during FIB-CVD growth stimulates erosion with directionality that produces surface modulations akin to those observed for sputtering. Just as a diamond surface roughens from 1-D ripples to 2-D steps with increasing angle of ion sputtering, so do ripples and steps appear on carbon-grown surfaces with increase in angle of FIB-CVD. Ion beam processing has been a stalwart of the microelectronics industry, is now a vital tool for research of self-organizing nanostructures, and promises to be a focus for future picotechnology.

Tailoring of micro/nano structures and surface functionalization are key goals in surface processing of materials. A new technology for a unique geometric precise 2D micro/nano design of grain architectures is presented. By means of super lateral grain growth crystalline lattice patterns such as line-, dot- and cross-like patterns were generated. The grain dimensions may be selected between a few nanometers and about 10 micrometers. The phase and grain formation was characterized by Electron Backscatter Diffraction with regard to orientation distribution and texture formation. Furthermore, dynamic aspects of this laser induced recrystallization process are studied, such as the heat transport in the films, comparing the vertical with the lateral solidification velocities by two-dimensional finite element method (FEM) simulations. Finally, the mechanical properties of the tailored thin films have been determined using nanoindentation experiments.

The effects of water on the wear resistance of 3 μm thick sputtered gold film on silicon substrate using contact AFM and a scanning nanoindenter were investigated. In performing wear tests on gold samples in the presence of water, a significant increase in depth of the wear area was observed compared to the same tests performed in the ambient atmosphere (∼55% humidity). These results were obtained using Hysitron Triboindenter on areas of 10×10 μm2 and an Atomic Force Microscope on areas of 1×1 μm2. Nanowear tests were preformed using silicon nitride cantilevers on the AFM and diamond Berkovich or blunt conical tips on the Hysitron. Normal loads used were 2000 μN and 10 μN, respectively. Tests performed in the ambient atmosphere resulted in a slightly reduced surface roughness, while a much higher wear rate was observed in the wear tests performed in water. Additionally, gold surface ripples formed under certain scanning conditions, in water for the Hysitron Triboindenter and in ambient atmosphere for the AFM. Nanoscale stick slip is being investigated as a possible explanation to the rippling phenomenon, and single scan line tests provide valuable information about the mechanisms and progression of the nanoscale wear.