Focused Ion Beam Nanolithography Research Articles

Template-assisted growth of Ga-based nanoparticle clusters on Si: effect of post-annealing process on the Ga ion beam exposed 2D arrays fabricated by focused ion beam nanolithography

We demonstrate template-assisted growth of gallium-based nanoparticle clusters on silicon substrate using a focused ion beam (FIB) nanolithography technique. The nanolithography counterpart of the technique steers a focussed 30 kV accelerated gallium ion beam on the surface of Si to create template patterns of two-dimensional dot arrays. Growth of the nanoparticles is governed by two vital steps namely implantation of gallium into the substrate via gallium beam exposure and formation of the stable nanoparticles on the surface of the substrate by subsequent annealing at elevated temperature in ammonia atmosphere. The growth primarily depends on the dose of implanted gallium which is in the order of 107 atoms per spot and it is also critically influenced by the temperature and duration of the post-annealing treatment. By controlling the growth parameters, it is possible to obtain one particle per spot and particle densities as high as 109 particles per square centimetre could be achieved in this case. The demonstrated growth process, utilizing the advantages of FIB nanolithography, is categorized under the guided organization approach as it combines both the classical top-down and bottom-up approaches. Patterned growth of the particles could be utilized as templates or nucleation sites for the growth of an organized array of nanostructures or quantum dot structures.

Review of: "Focused ion beam nanolithography , as a sequential nanolithography technique, is inherently slow and its throughput is much lower than other techniques, and Ga + -based liquid metal ion source"

Review of: "Focused ion beam nanolithography , as a sequential nanolithography technique, is inherently slow and its throughput is much lower than other techniques, and Ga + -based liquid metal ion source"

Sharp High-Aspect-Ratio AFM Tips Fabricated by a Combination of Deep Reactive Ion Etching and Focused Ion Beam Techniques

The shape and dimensions of an atomic force microscope tip are crucial factors to obtain high resolution images at the nanoscale. When measuring samples with narrow trenches, inclined sidewalls near 90 degrees or nanoscaled structures, standard silicon atomic force microscopy (AFM) tips do not provide satisfactory results. We have combined deep reactive ion etching (DRIE) and focused ion beam (FIB) lithography techniques in order to produce probes with sharp rocket-shaped silicon AFM tips for high resolution imaging. The cantilevers were shaped and the bulk micromachining was performed using the same DRIE equipment. To improve the tip aspect ratio we used FIB nanolithography technique. The tips were tested on narrow silicon trenches and over biological samples showing a better resolution when compared with standard AFM tips, which enables nanocharacterization and nanometrology of high-aspect-ratio structures and nanoscaled biological elements to be completed, and provides an alternative to commercial high aspect ratio AFM tips.

Focused Ion Beam in Thermal Science and Engineering

Laboratory of Thermodynamics, ETH Zurich CH-8092 Switzerland In this paper, utilizing a focused ion beam source for applications in thermal science is demonstrated. Focused-ion-beam (FIB) nanolithography has been used to make electrical contacts on nanometer-sized materials. However, a foreseeable damage occurring in these materials by highly energetic ion bombardment during metal deposition restrains its use. The appearance of the dual beam (conventional FIB with a scanning electron microscope) has facilitated the use of dual-beam FIB nanolithography owing to the possibility of acquiring electron beam images in situ and dissociating metalorganic compounds, giving rise to electron-beam-induced metal deposition [1]. Because interaction between electrons and the sample is less destructive than using ions, performing an electron-assisted deposition on the nanostructure can minimize undesired surface damage and structure modification of the nanostructure. The thermal properties of individual multi-walled carbon nanotubes was measured by utilizing the 4-point-probe 3-ω method, based on the fact that the third harmonic amplitude and phase as a response to applied alternate current at fundamental frequency, ω, can be expressed in terms of thermal conductivity and diffusivity. To this end, a microfabricated device composed of four metal electrodes was modified to manufacture nanometer-sized wires by using a focused ion beam source as shown in Fig. 1a. A carbon nanotube could then be suspended over a deep trench milled by the focused ion beam, preventing heat loss to the substrate (Fig. 1b). To deposit individual carbon nanotubes, we utilized the principle of dielectrophoresis (DEP). The dielectrophoresis has been considered as an excellent method for CNT manipulation. Herein, we applied a high-frequency (5 MHz) ac field combined with dc offset between the pads, 1 and 4. When a CNT touches the electrodes, it will stick to them and stays there by Van der Waals force [2]. Finally, to minimize the electrical contact resistance between carbon nanotubes and the metal electrodes, electron beam “soldering” was performed. The pads 1 and 4 have round shapes on the tip, which aids carbon nanotube deposition. Fig. 2 shows three different measurements of 3-ω signals for carbon nanotubes submerged in vacuum, air and deionized water. To this end, the 4-wire configuration (Fig. 1c) was utilized for measuring the 3

Formation and ordering of Ge nanocrystals on SiO 2 using FIB nanolithography

We first investigate the spontaneous formation of nanometric and highly dense (∼3×10 12 cm −2) Ge droplets on SiO 2/Si(0 0 1) by scanning tunnelling microscopy and spectroscopy. Ge dots are grown using a two-step process: first, Ge deposition on the clean SiO 2 surface at room temperature (RT) and second, thermal annealing at 500 °C. Ge dots appear free of germanium oxides. Then we show the ordering of Ge nanocrystals (NCs) on SiO 2/Si(0 0 1) substrates patterned by focused ion beam (FIB). Lateral ordering of the ultra-dense Ge nanodots was achieved by the combination of the following technological steps: (a) use of a FIB to create ordered two-dimensional (2D) arrays of regular holes on a field oxide on the silicon substrate, (b) chemical cleaning and restoring of the Si surface in the holes, (c) further oxidation to transfer the pattern from the field oxide to the silicon substrate, (d) removal of the field oxide and thermal re-oxidation of the sample in order to create a tunnelling oxide of homogeneous thickness on the patterned silicon surface and (e) self-assembly of the 2D arrays of Ge dots on the patterned tunnelling oxide. We show that Ge NCs are ordered in the FIB holes whatever is their dimension/density.