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Structures based on suspended graphene are promising elements for problems in photonics and sensory electronics due to the possibility of the elimination of trap states in the substrate and the increase in the speed and sensitivity of the graphene layer. The development of techniques for introducing carbon nanostructures in silicon technology to create micro- and nanoelectronic devices is also relevant. In this paper, the features of the technique for the formation of a silicon membrane and pores in it, as well as the deposition of graphene on silicon membranes, are presented. The Raman spectra of suspended graphene showing a shift of the G-peak by 4.5 cm–1 and the 2D peak by 7.5 cm–1 relative to the peaks of the graphene lying on silicon are obtained. Using the curves of the approach and retraction of the probe of an atomic force microscope, the possible deflection of the suspended graphene is studied, showing the distances at which the attractive and repulsive forces are located in the probe–suspended graphene system. It is established that the significant deflection of graphene, by 1 µm at a pore diameter of 5 µm, makes laser focusing is difficult. This primarily affects the use of such structures as a base for a gas or fluid sensor of various organic compounds, as well as for suspended graphene-based transistors. [ABSTRACT FROM AUTHOR]

Polymer membranes are conventionally prepared using high-energy particles from radioactive decay or by the bombardment of hundreds of MeVs energy ions. In both circumstances, tracks of damage are produced by particles/ions passing through the polymer, and successively, the damaged material is removed by chemical etching to create narrow pores. This process ensures nanosized pore diameter but with random placement, leading to non-uniform local pore density and low membrane porosity, which is necessary to reduce the risk of their overlapping. The present study is focused on the use of polyethylene terephthalate (PET) foils irradiated by 10.0 MeV carbon ions, easily achievable with ordinary ion accelerators. The ion irradiation conditions and the chemical etching conditions were monitored to obtain customized pore locations without pore overlapping in PET. The quality, shape, and size of the pores generated in the micromembranes can have a large impact on their applicability. In this view, the Scanning Transmission Ion Microscopy coupled with a computer code created in our laboratory was implemented to acquire new visual and quantitative insights on fabricated membranes. [ABSTRACT FROM AUTHOR]

Lithographic methods are used in forming contacts for nanostructures smaller than 100 nm, in particular, electron-beam lithography and focused-ion-beam lithography with an electron-sensitive resist. Focused-ion-beam lithography is characterized by a greater susceptibility to a resist, a high value of backscattering and the proximity effect, the best ratio of performance and contrast to the minimal size of the exposed elements as compared to electron-beam lithography. In this work, the method of ultrathin-resist exposure to a focused ion beam is developed. The dependence of the electron-sensitive-resist thickness on the degree of its toluene dilution is established. It is shown that electron-sensitive resist thinning to 30 nm based on α-chloro-methacrylate with α-methylstyrene allows the formation of metal contacts with a 500-nm gap over 30 μm. Silicon nanostructures within a metallic submicron gap are obtained on a dielectric substrate. The configuration of the obtained nanostructures is investigated by optical, electron, ion, and probe microscopy. It is established that it is possible not to use an additional alignment marks when nanoscale field-effect transistors are fabricated on the basis of silicon nanostructures. [ABSTRACT FROM AUTHOR]

Routinely, in membrane technology, the decay from radioactive particles or the bombardment of ions with MeV energy per nucleon have been employed for the production of narrow and long pores in membranes. Presently, the ion lithography is proposed to make the fabrication cost more affordable. It is prospective for the use of medium capacity accelerators making more feasible the fabrication of customized membranes. Thin polyethylene terephthalate foils have been patterned using 12 MeV O5+ ions and then processed to obtain good aspect ratio ion track pores in membranes. Pores of micrometric diameter with the following profiles were fabricated in the membranes: truncated cone, double conical, ideal cone, and cylindrical. Monitoring of the shape and size of pores has been attempted with a combination of Scanning Transmission Ion Microscope and a newly designed simulation program. This study is focused on the use of low-energy ions, accomplished in all laboratories, for the fabrication of membranes where the pores are not randomly traced and exhibit higher surface density and negligible overlapping than in membranes commonly manufactured. The good reproducibility and the ordered pore locations can be potentially utilized in applications such as microfluidics and organ-on-chip microsystems, where cells growing over porous substrates are used in simulation of biological barriers and transport processes. [ABSTRACT FROM AUTHOR]

One of the ways to use a focused ion beam in lithographic processes to create nanostructures is through the exposure of special sensitive materials, i.e., resists. As a result of exposure, the solubility of such a material increases ("positive" resist) or, conversely, decreases ("negative" resist). Subsequent selective irradiation and development of the resist make it possible to create a predetermined pattern on the substrate. This work is aimed at developing the theoretical foundations for this ion lithography method. A practically important case of stopping heavy ions in an organic resist, the average atomic mass of which is much less than the mass of the incident ion, is considered. Expressions for the "energy" and transport lengths of ions are obtained. The calculations are carried out assuming a power-law interaction potential. The "energy" length characterizes the depth of penetration of ions into the material, and the transport length is related to beam expansion due to scattering. Therefore, these lengths are the main characteristics of the zone in which the ion-beam energy is absorbed. [ABSTRACT FROM AUTHOR]

Polymer membranes are conventionally prepared using high-energy particles from radioactive decay or by the bombardment of hundreds of MeVs energy ions. In both circumstances, tracks of damage are produced by particles/ions passing through the polymer, and successively, the damaged material is removed by chemical etching to create narrow pores. This process ensures nanosized pore diameter but with random placement, leading to non-uniform local pore density and low membrane porosity, which is necessary to reduce the risk of their overlapping. The present study is focused on the use of polyethylene terephthalate (PET) foils irradiated by 10.0 MeV carbon ions, easily achievable with ordinary ion accelerators. The ion irradiation conditions and the chemical etching conditions were monitored to obtain customized pore locations without pore overlapping in PET. The quality, shape, and size of the pores generated in the micromembranes can have a large impact on their applicability. In this view, the Scanning Transmission Ion Microscopy coupled with a computer code created in our laboratory was implemented to acquire new visual and quantitative insights on fabricated membranes.

Routinely, in membrane technology, the decay from radioactive particles or the bombardment of ions with MeV energy per nucleon have been employed for the production of narrow and long pores in membranes. Presently, the ion lithography is proposed to make the fabrication cost more affordable. It is prospective for the use of medium capacity accelerators making more feasible the fabrication of customized membranes. Thin polyethylene terephthalate foils have been patterned using 12 MeV O5+ ions and then processed to obtain good aspect ratio ion track pores in membranes. Pores of micrometric diameter with the following profiles were fabricated in the membranes: truncated cone, double conical, ideal cone, and cylindrical. Monitoring of the shape and size of pores has been attempted with a combination of Scanning Transmission Ion Microscope and a newly designed simulation program. This study is focused on the use of low-energy ions, accomplished in all laboratories, for the fabrication of membranes where the pores are not randomly traced and exhibit higher surface density and negligible overlapping than in membranes commonly manufactured. The good reproducibility and the ordered pore locations can be potentially utilized in applications such as microfluidics and organ-on-chip microsystems, where cells growing over porous substrates are used in simulation of biological barriers and transport processes.

Vertically aligned self-assembled nanocomposite films have provided a unique platform to study magnetoelectric effects and other forms of coupling between complex oxides. However, the distribution in the locations and sizes of the phase-separated nanostructures limits their utility. In this work, we demonstrate a process to template the locations of the self-assembled structure using ion lithography, which is effective for general insulating substrates. This process was used to produce a nanocomposite consisting of fin-shaped vertical nanostructures of ferroelectric BiFeO 3 and ferrimagnetic CoFe 2 O 4 with a feature size of 100 nm on (111)-oriented SrTiO 3 substrates. Cross-sectional imaging of the three-phase perovskite-spinel-substrate epitaxial interface reveals the selective nucleation of CoFe 2 O 4 in the trenches of the patterned substrate, and the magnetic domains of CoFe 2 O 4 were manipulated by applying an external magnetic field.

We demonstrate a prototype of a Focused Ion Beam machine based on the ionization of a laser-cooled cesium beam and adapted for imaging and modifying different surfaces in the few-tens nanometer range. Efficient atomic ionization is obtained by laser promoting ground-state atoms into a target excited Rydberg state, then field-ionizing them in an electric field gradient. The method allows obtaining ion currents up to 130 pA. Comparison with the standard direct photo-ionization of the atomic beam shows, in our conditions, a 40-times larger ion yield. Preliminary imaging results at ion energies in the 1–5 keV range are obtained with a resolution around 40 nm, in the present version of the prototype. Our ion beam is expected to be extremely monochromatic, with an energy spread of the order of the eV, offering great prospects for lithography, imaging and surface analysis. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) foils have been covered with poly(dimethylsiloxane) (PDMS) via spin coating and then heated in oven to strengthen the bond of the polymerized composite. Micro ion beam has been used to directly pattern the realized film and to promote the localized reduction in the ion irradiated GO areas in vacuum. The lessening of the disorder in the carbon crystal structure and the defects production are demanding in all the graphene-based materials applications. Micro beams of 5 MeV C3+ ions with a spot of 1.5 μm × 10 μm (focused beam) and unfocused beams with size of 3 × 3 mm2 have been employed to irradiate the produced composites on a small localized region and wide areas respectively. The poly(dimethylsiloxane) foil, used to cover GO, confers flexibility to the created patterns and allows the oxygen degassing from GO. The quality and the fidelity of the patterns have been investigated by Atomic Force Microscopy (AFM). The ion beam induced structural changes in the coated and uncoated graphene oxide foils have been studied by Raman spectroscopy confirming that PDMS can be used as protecting layer to improve the quality of patterns obtained on graphene oxide by the 5.0 MeV C3+ ions beam writing. • The polydimethylsiloxane as a coating of material improves the quality of the patterns realized by the ion lithography. • Good quality of reduced graphene oxide (rGO) due to its permeability to oxygen. • Better homogeneity of the distribution of ions current during the patterning process. • Lessening of the defects generation and the relaxation effects of the GO during the patterning by 5 MeV energy of heavy ions. • Better performance of the capacitance prepared by ion-beam writing on GO covered with PDMS. [ABSTRACT FROM AUTHOR]

Abstract: The last decade has seen proton beam writing maturing into a versatile lithographic technique able to produce sub-100nm, high aspect ratio structures with smooth side walls. However, many applications in the fields of photonics and fluidics require the fabrication of structures with high spatial resolution that extends over several centimetres. This cannot be achieved by purely magnetic or electrostatic beam scanning due to the large off-axis beam aberrations in high demagnification systems. As a result, this has limited us to producing long straight structures using a combination of beam and stage scanning. In this work we have: (1) developed an algorithm to include any arbitrary pattern into the writing process by using a more versatile combination of beam and stage scanning while (2) incorporating the use of the ubiquitous AutoCAD DXF (drawing exchange format) into the design process. We demonstrate the capability of this approach in fabricating structures such as Y-splitters, Mach-Zehnder modulators and microfluidic channels that are over several centimetres in length, in polymer. We also present optimisation of such parameters as scanning speed and scanning loops to improve on the surface roughness of the structures. This work opens up new possibilities of using CAD software in PBW for microphotonics and fluidics device fabrication. [Copyright &y& Elsevier]

Abstract: Fast heavy ion beam-based lithography using masks of self-assembled materials has been applied for transferring well-ordered nano- and micropatterns to rutile TiO2 single crystals. As the induced damage has a high etching selectivity the patterns can be developed in hydrofluoric acid with very high-contrast. Here we present resulting patterns when using a mask of self-ordered silica spheres. The obtained pattern are replicas of the mass distribution of the mask. In addition the shape and size of the regular structures depend on the applied ion energy and fluence. Direct modifications of the optical properties of TiO2 in a well-defined pattern are also presented. [Copyright &y& Elsevier]

Abstract: A method for producing ordered carbon nanopillar arrays is presented. The method is based on ion irradiation through a small anodic porous alumina membrane, resulting in carbon deposition within the centers of the pores on a gold covered substrate. Samples were irradiated by 4MeV ions with fluences of . The combined use of pick’n place positioning of the small porous alumina templates and ion beam irradiation is well suited for post-processing on silicon based integrated circuits. It provides fast local deposition at low temperature of high-density ordered carbon nanopillar arrays in larger silicon based systems, e.g., for field emitting or biosensors applications. [Copyright &y& Elsevier]

Abstract: Heavy ion lithography using self-assembled colloidal particles as a mask enables micro- and nano-patterning of surfaces. The resulting patterns can be tuned by varying the mask configuration, i.e. packing geometry of the colloidal particles and number of particle layers. In this work we present several patterns, which can be transferred to rutile TiO2 single crystals by irradiating through self-assembled layers of silica micro-spheres with 25MeV Br ions. As the induced ion tracks in TiO2 have a very high etching selectivity the patterns can be developed in HF with very high contrast. This makes it possible to prepare large patterned areas which can be of interest for e.g. optical applications. [Copyright &y& Elsevier]

Abstract: The feasibility of electrostatically extracting and accelerating ions from room temperature ionic liquids in a high vacuum environment is investigated using externally wetted emitters similar to those manufactured for liquid metal ion sources, made out of tungsten wire and electrochemically treated to produce a sharp tip and to increase surface wettability. The ionic liquid EMI-BF4 is used as a prototypical example. The temperature dependence on emission current suggests that liquid flow over the metallic surface is limited by viscosity. Time-of-flight spectrometry indicates that the beam is composed of and (EMI-BF4)EMI+ ions in the positive polarity and and (EMI-BF4) ions in the negative polarity, and that these ions are emitted with energies very close to their applied potentials. Angular distribution measurements in positive and negative polarities show that ions travel near the propagation axis, diverging by not more than 18° from the centerline. Thanks to the extraordinary variety of ionic liquids it should be possible to generate a correspondingly large number of bipolar nonmetallic ion beams each with unique properties and applicability in fields as diverse as ion lithography, analytical equipment and space propulsion. [Copyright &y& Elsevier]

Ordered nanoporous alumina samples with a pore diameter of 70 nm, an array period of 100 nm and several thicknesses were considered as possible masks for pattern transfer by MeV ion lithography. A simple procedure for the sample alignment using a 2 MeV He+ beam was utilized. The energy distributions of transmitted ions as well as backscattering spectra were studied in aligned and non-aligned orientations. The best transmission, comparable to the relative surface area covered by pores, was reached for 2 μm thick samples and was independent on ion species. Although the transmission for thicker membranes was generally lower, it significantly depended on the quality of each individual sample. The presented ion beam technique can therefore be used as a tool for the characterization of porous materials. The acceptance angle for transmission through pores and the effective atomic density of samples can be obtained from the experimental data and it is shown that nanoporous alumina can be used as a mask for MeV ion lithography. [Copyright &y& Elsevier]

The paper discusses possible ways of increasing beam brightness in ion injectors. The argon/helium ion injector comprising a newly designed RF ion source and, a Wien filter has been designed for use in accelerator-based nanoprobe facilities. The phase set degradation due to aberrations in the injector ion-optic system was simulated with allowance for multipole and fringing fields. The RF ion sources with different permanent magnet systems were tested. Experiments were performed with argon and helium. A plasma density of up to 3×1011 cm−3 and beam brightness of ∼100 A/(m2 rad2 eV) were obtained. The ion current density inside an extracting electrode in the source was 10 mA/cm2 for an emission hole diameter of 0.6 mm. Measurements of the current value and emittance were performed with ion source testing equipment permitting measurements of the ion beam current, emittance, mass composition, and RF power input into the plasma. [Copyright &y& Elsevier]