We present a closed approach towards direct microstructuring and high precision prototyping with focused ion beams (FIB). The approach uses the simulation of the involved physical effects and the modeling of geometry/topography during milling while the ion beam is steered over the surface. Experimental examples are given including the milling of single spots, trenches, rectangles, and Fresnel lenses. Good agreements between simulations and experiments were obtained. The developed procedures can also be applied to other FIB prototyping examples.

Carbon nanotubes (both the single- and multi-walled), in the family of nanostructured carbons, are of great interest because of several unsurpassable physical properties and it needs to be shown that they are physically stable and structurally unaltered when subjected to radiation. In addition to testing them for space applications, when exposed to high energy electron beam from transmission electron microscopy, the results seem quite promising in terms of nano-engineering/ nano-manufacturing for producing novel nanocarbons [1-3]. Experimental studies of effects of electron beam irradiation on carbon nanotubes show that multi-walled ones tend to be relatively more robust than their single-walled kins. The increased exposure on an individual bundle of single-wall nanotubes promoted graphitization, pinching, and cross-linking analogous to polymers forming an intra-molecular junction (IMJ) within the area of electron beam focus, possibly through aggregates of amorphous carbon [2,3]. Formation of novel nanostructures (nano-ring and helix-like) due to irradiation are observed. These studies shed light on the dynamics of nanomanufacturing and a regime of possible relevance of these materials for: (i) short-term space missions; (ii) radiation hard programmable logic circuits; and (iii) radiation pressure sensors. It is suggestive that a local reorganization occurs. Through resonance Raman spectroscopy and related techniques we also elucidate an important notion of global topology and curvature at nanoscale which points to an emergent paradigm of Curvature/Topology → Property → Functionality in these technologically important geometries of carbons: nanotubes, fullerenes, nanorings, nanocones, nanohorns and nanodisks. To this end, we have determined the variation in first order high frequency Raman band which indicates a strong electron-phonon coupling. These concepts also apply to nanostructures of other “topological materials” such as BN nanotubes and nanotori, helical gold nanotubes as well as Möbius conjugated polymers.

This study is motivated by recent applications of short laser pulses to the manipulation of atomic structures at the atomic scale and is based on the Density Functional Theory. The structures considered are linear monoatomic chains, formed by covalent and metallic atoms, and the calculations illustrate their evolution under laser irradiation. The calaculations show that the modification of the chain structure spans from a slight relaxation of the interatomic distances to fragmentation and illustrate the times and energies needed to induce those changes.

Self assembled gold nanoclusters are attractive building blocks for future nanoscale sensors and optical devices due to their exciting catalytic properties. Recently several methods have been employed to produce nanoclusters on solid substrates, which result in a random spatial distribution of the clusters. In this work, we have achieved ordered circular patterns of gold nanoclusters in Silicon (100) substrates by Au ion implantation followed by thermal annealing. This unique phenomenon is observed only above a critical threshold implantation dose and anneal temperature. Based on a systematic study (SEM, XTEM and XRD) of the growth and morphology of the nanoclusters, we propose a tentative model for the formation mechanism of this unusual self-assembled pattern.

In this study, self-organized growth of gold nanoparticles dispersed in amorphous alumina matrices was investigated. Au/Al2O3 multilayered structures were grown on silicon (001) substrates using pulsed laser deposition. Vertical ordering of particles was examined with cross-sectional transmission electron microscopy and image Fourier transformation. Self-organization of gold nanoparticles along the vertical direction was observed in the samples grown at room temperature and 320 °C. This process occurred through two-different growth modes, known as top-on-top growth and top-on-middle growth. The driving force for the vertical ordering was attributed to long-range elastic interactions among nanoparticles during the film deposition process.

The effects of ultraviolet irradiation on a heteroleptic titanium alkoxide ((OPy)2Ti(4MP)2) have been investigated. The molecule has been studied in solution and in thin film form using FTIR and Raman spectroscopies. Quantum computational modeling was used to associate vibrational modes with structural moieties present in the molecule. In all cases examined, a preferential photoinduced modification in vibrational resonances linked to the 4-mercaptophenol (4MP) ligand was observed. In contrast, little or no change was exhibited in the vibrational structure of the OPy ligands.

Dewetting instabilities in nanoscopic Co films, induced by uniform multiple ns pulse laser irradiation, leads to a system of nanoparticles with robust spatial order. On the other hand, irradiation by non-uniform laser intensity, such as with a two beam laser interference pattern generates a quasi two-dimensional pattern of nanoparticles possessing long range order (LRO) and short range order (SRO). Here we discuss the various instabilities that are responsible for the production of these dissimilar patterns and length scales on the basis of their time scales. For the case of single beam irradiation, the film progresses in a manner that can be attributed to classical spinodal dewetting. Pattern formation from interference irradiation is the result of time scale-based selection of competing processes, which can be chosen by controlling the film thickness. This approach promises a simple and cost-effective means to self-assemble various nanostructures.

We studied the effects of phosphorus (P) on Ni nanocrystalline morphology formed by focused ion beam (FIB) irradiation for Ni-P amorphous alloy thin films. The P content in the amorphous alloy was varied from 8 to 12 wt.%. The nanocrystals induced by the FIB irradiation for Ni-11.8, 8.9, 7.9 wt.% amorphous alloy had an f.c.c. structure and showed unique crystallographic orientation relationships to the geometry of the focused ion beam, that is, {111}f.c.c. parallel to the irradiated plane and <110>f.c.c. parallel to the projected ion beam direction, respectively. The Ni nanocrystals precipitated like aggregates with decreasing of the P content. These results represent that the P content does not affect crystallographic orientation relationships, while influences the precipitation distribution of Ni nanocrystals generated by the FIB irradiation.

Spatially ordered patterns result under ns laser-induced dewetting of nanoscopic metallic films like Co and Ag on inert substrates like SiO2. In both cases, the observed ordering length scale is due to thin film hydrodynamic instability with spinodal-like character. However, the morphological pathway during dewetting is different for the two metals: occurring through development of bicontinuous structures in the case of Ag and by progression of cellular networks for Co. Dewetting in bilayer structures of Ag and Co on SiO2 show that the morphology evolution is dictated by the thicker of the two films in the bilayer structure. We applied linear stability analysis to predict the length scales in single and bilayer metal film. The experimental observations are in good agreement with theoretical predictions from the analysis. An important result was that the length scales for the bilayer film were significantly smaller than a single layer of the same thickness suggesting that further control of patterning length scales may be achieved through multilayer dewetting.

An alternative method for seeding catalyst nanoparticles for carbon nanotubes and nanowires growth is presented. Ni nanoparticles are formed inside a 450 nm SiO2 film on (100) Si wafers through the implantation of Ni ions at fluences of 7.5×1015 and 1.7×1016 ions cm−2 and post-annealing treatment at 700, 900 and 1100 °C. After exposed to the surface by HF dip etching, the Ni nanoparticles are used as catalyst for the growth of vertically aligned carbon nanotubes by direct current plasma enhanced chemical vapor deposition.

We present new experimental results regarding the surface defect structure of ion bombarded gold surfaces. We report annealing mechanisms of surface defects on reconstructed Au(001) after medium fluence ion bombardment. We show how (001) and (111) gold surfaces can be nanostructured with a certain degree of lateral order by means of high fluence and high flux ion irradiation. We prove that ion irradiation nanostructuring strongly changes optical (plasmonic) properties of gold polycrystalline thin films.

The ion irradiation of the Rh(110) surface results in the self-organised formation of various nano-structured morphologies like ripples, mounds, pyramids which have been thoroughly studied as a function of the incidence angle and of the impact energy of the impinging ions. A study of the evolution of the surface ripples at various impact energies above the hot-spot threshold, has been rationalized in terms of a contribution due to an ion-induced surface diffusion mechanism. In the very low ion incidence regime, where the formation of hot spots following ion impact is inhibited, the formation of a rhomboidal pyramid pattern is singled out and attributed to the predominant reorganization of surface adatom and vacancies produced in the topmost surface layers. The metastable rhomboidal pyramid pattern, was recently proven to have extraordinary chemical reactivity since it is endowed with a very high density of undercoordinated step sites runnin along the very open <1-12> azimuthal direction.

Ion beams have been used to modify surface topography, producing nanometer-scale modulations (and even subnanometer ripples in this work) that have potential uses ranging from designing self-assembly structures, to controlling stiction of micromachined surfaces, to providing imprint templates for patterned media. Modern computer-controlled Focused Ion Beam tools enable alternating submicron patterned zones of such ion-eroded surfaces, as well as dramatically increasing the rate of ion beam processing. The DualBeam FIB/SEM also expedites process development while minimizing the use of materials that may be precious (Diamond) and/or produce hazardous byproducts (Beryllium). A FIB engineer can prototype a 3-by-3-by-3 matrix of variables in tens of minutes and consume as little as zeptoliters of material; whereas traditional ion beam processing would require tens of days and tens of precious wafers. Saturation wavelengths have been reported for ripples on materials such as single crystal silicon or diamond (∼200nm); however this work achieves wavelengths >400nm on natural diamond. Conversely, Be can provide a stable and ordered 2-dimensional array of <40nm periodicity. Also ripples <0.4nm are fabricated on carbon-base surfaces, and these quantized picostructures are measured by HR-TEM and electron diffraction. Rippling is a function of material, ion beam, and angle; but is also controlled by chemical environment, redeposition, and aspect ratio. Ideally a material has a constant yield (atoms sputtered off per incident ion); however, pragmatic FIB processes, coupled with the direct metrological feedback in a DualBeam tool, reveal etch rates do not remain constant for nanometer-scale processing. Control of rippling requires controlled metrology, and robust software tools are developed to enhance metrology. In situ monitoring of the influence of aspect ratio and redeposition at the micron scale correlates to the rippling fundamentals that occur at the nanometer scale and are controlled by the boundary conditions of FIB processing.

The control of formation and ordering of self assembled nanostructures, with medium- to long-range order, is a challenge that limits advances in many fields of nanotechnology. We have developed a technique, which we call fluctuation x-ray microscopy, that offers quantitative insight into medium-range correlations in disordered materials at nanometer- and larger-length scales. We examined the influence of sol-gel process variables on medium range order in PI-b-PEO/ aluminosilicate bulk using this technique. The nano-structuring of inorganic materials was directed by polymer self-assembly. The medium range correlation between the nanostructures in two hybrids was quantitatively examined and compared.

This paper presents the model for pattern formation in the course of thermodynamically stable and unstable crystal growth from vapor phase, which is influenced by rapid spatio-temporal variations of substrate and film temperature. In the model, such variations result from the interference heating of a substrate by weak pulsed laser beams. In the thermodynamically stable case the surface relaxational dynamics is influenced by surface diffusion mass transport from hot to cold regions of a substrate; this leads to accumulation of mass in cold regions and depletion in hot regions. In the thermodynamically unstable case the underlying faceting (spinodal) instability coupled to diffusion mass fluxes from hot to cold regions leads to formation of pyramidal surface structures. The scale of stationary coarsened structure increases as the separation distance of the adjacent interference fringes decreases (relative to the intrinsic faceting wave length, which is determined by the balance between the corner regularization energies and the surface energy anisotropy). On the other hand, the coarsening rates decrease with decreasing the separation distance, at least at particular typical deposition strength. The deposition strength and the separation distance of the interference fringes determine the transient and stationary pattern shape. By effectively redistributing adatoms on a substrate through the enhanced, spatially inhomogeneous diffusion, the interference heating mechanism delays, for large separation distances, the onset of spatiotemporal chaos as the growth rate increases.

Nano-graphitization from amorphous carbon state is assisted by the electron beam irradiation. An inter-columnar region in the amorphous carbon films with low atomic and electron densities is controlled to have a graphitic structure with relatively low dose electron beam irradiation. This amorphous carbon ? beam interaction generates a new type of carbon hybrids where amorphous carbon phase columns are sustained by the graphitic inter-columnar network. This hybrid film has an exotic mechanical and tribologic response: extraordinary reversible deformability up to 8 – 10 % normal strain, high wearing resistance and low friction at high normal pressure. A combination of iron implantation with this electron irradiation provides us the other nano-graphitization process. An amorphous carbon film including the implanted iron atoms is chemically modified to have a columnar graphitic structure by the electron beam irradiation. In this post-implantation electron beam irradiation, the basic graphitic units with 1-2 nm in size are controlled to align vertically along the film thickness. This type of nano-graphitization has a strong dependency on the iron doses before electron beam irradiation. The above two types of nano-graphitization provides us a new tool to explore the functionalized structural thin films in application.

We have used highly charged ions (HCIs) such as Xe44+ to modify ultrathin aluminum oxide barriers in magnetic tunnel junctions (MTJs) in order to controllably adjust their electrical properties independently of oxide thickness. We have reduced the resistance area (RA) product of our MTJ devices by up to three orders of magnitude down to our present measurement uncertainty limit of 30 Ω·μm2 by varying the HCI dose. Preliminary experiments indicate that HCI modified Co/Al2O3/Co MTJs have a reduced magnetoresistance (MR) of ≈ 1% at room temperature as compared to ≈ 10% for undosed devices. The goal of this effort is to fabricate a magnetic field sensor in current-perpendicular-to-plane (CPP) geometry with an RA optimized for hard drive read heads. This is an improvement over presently demonstrated CPP architectures based on giant magnetoresistance or tunnel junctions, whose RAs are either to low or too high.

Thin polymer films containing metal nanoparticles were irradiated with linearly polarized femtosecond laser pulses. The resulting laser-induced periodic modification of the nanoparticle assemblies was studied by using scanning and transmission electron microscopy. The structure period Lambda is correlated with the applied laser wavelength lambda by Lambda = 0.7 lambda. The effect was observed for gold, silver and copper nanoparticles. Optical spectra of the laser-irradiated films show a clear dichroism.

Ion bombardment was used during and after the deposition of controlled-porosity thin films produced using the Glancing Angle Deposition (GLAD) technique. Post-deposition ion bombardment was used to mill vertical-post morphology GLAD films, whose constituent columns varied in size due to competition effects. Smaller columns, although in the minority, can have a significant impact on the function of these films in a variety of optics applications, and can only be avoided by pre-selecting column location (i.e. seeding). Uniform milling eliminated smaller columns and left only remnants of the largest columns, which then acted as seeds during subsequent depositions. This simple, non-lithographic technique leads to more uniform column morphology. Column tilt angle can also be adjusted using ion bombardment. Methods to tune column tilt angle as a function of ion current using ion-assisted deposition are discussed, with an emphasis on improved square spiral photonic band gap crystal fabrication. Ion bombardment was found to increase the tilt angle of each spiral arm, moving the architecture closer to the theoretical optimum structure.