Jun-ichi Fujita

Three-dimensional nanostructure fabrication by focused-ion-beam chemical vapor deposition

Three-dimensional nanostructure fabrication has been demonstrated by 30 keV Ga+ focused ion beam assisted deposition using a aromatic hydrocarbon precursor. The characterization of deposited film on a silicon substrate was performed by a transmission microscope and Raman spectra. This result indicates that the deposition film is a diamondlike amorphous carbon. Production of three-dimensional nanostructure is discussed. Microcoil, drill, and bellows with 0.1 μm dimension were fabricated as parts of the microsystem. Furthermore, microstructure plastic arts is advocated as a new field using microbeam technology, presenting one example of a microwine glass with 2.75 μm external diameter and 12 μm height.

ULTRAHIGH RESOLUTION OF CALIXARENE NEGATIVE RESIST IN ELECTRON BEAM LITHOGRAPHY

A nonpolymer material, calixarene derivative (hexaacetate p‐methnylcalix[6]arene) was tested as a high‐resolution negative resist under an electron beam lithography process. It showed under 10‐mm resolution with little side roughness and high durability to halide plasma etching. A sub‐10‐nm Ge quantum wire was perfectly etched off without defects. Such a performance is suitable for nanoscale device processes.

Patterns in the bulk growth of carbon nanotubes

Abstract The growth of nanotubes in carbon arc plasma is described in detail. The structure and organization of the nanotube deposits observed by SEM and AFM reveal a fractal-like pattern of growth. One of the key units of growth appears to be the micro-bundle composed of neatly packed and aligned nanotubes. The micro-bundle together with the field and current might explain the high formation yield of nanotubes.

Free-space-wiring fabrication in nano-space by focused-ion-beam chemical vapor deposition

Focused-ion-beam chemical vapor deposition (FIB-CVD) is an excellent technology for forming three-dimensional nanostructures. Various diamond-like-carbon (DLC) free-space-wirings have been demonstrated by FIB-CVD using a computer-controlled pattern generator, which is a commercially available pattern generator for electron-beam (EB) lithography. The material composition and crystal structure of DLC free-space-wiring were studied by transmission-electron microscopy and energy-dispersive x-ray spectroscopy. As a result, it became clear that DLC free-space-wiring is amorphous carbon containing a Ga core in the wire. Furthermore, the electrical resistivity measurement of DLC free-space-wiring was carried out by two terminal electrodes. Au electrodes were fabricated by EB lithography and a lift-off process. The electrical resistivity was about 100 Ω cm at room temperature.

Observation and characteristics of mechanical vibration in three-dimensional nanostructures and pillars grown by focused ion beam chemical vapor deposition

The Young’s modulus of diamond-like carbon (DLC) pillars was measured by means of mechanical vibration using scanning electron microscopy. The DLC pillars were grown using Ga+ focused ion beam-induced chemical vapor deposition with a precursor of phenanthrene vapor. The Young’s modulus of the DLC pillars was around 100 GPa at vapor pressure of 5×10−5 Pa and it had a quality (Q) value of resonance exceeding 1200. There seemed to be a balance between the DLC growth rate and surface bombardment by the ions, and this played an important role in the stiffness of the pillars. Some of the DLC pillars showed a very large Young’s modulus over 600 GPa at low gas pressure conditions.

Preferentially oriented epitaxial Y-Ba-Cu-O films prepared by the ion beam sputtering method

Preferentially oriented epitaxial Y‐Ba‐Cu‐O films were prepared on (100) SrTiO3 substrates by oxygen reactive ion beam sputtering. The epitaxial orientations were varied by controlling both substrate temperature and oxygen parital pressure. c‐axis oriented films tended to be formed at higher substrate temperatures (>620 °C) and lower oxygen pressures ( 3×10−3 Torr). The best Tc (end) of 82 K was observed in one of the c‐axis oriented film without post‐annealing. The tendency for preferential orientation can be well understood in terms of the lattice mismatch between the substrate and the film, the lattice constants of which depend on oxygen deficiency.

Room temperature replication in spin on glass by nanoimprint technology

A compact nanoimprint lithography (NIL) system using the driving power of a stepping motor has been developed. Compared to a conventional NIL system with a hydraulic press, there are some additional features of the NIL system such as compactness and low cost. We propose the use of spin on glass (SOG) instead of PMMA to avoid thermal expansion and demonstrate SOG patterns with 200 nm linewidths at room temperature replications using the NIL system. The SOG patterns were transferred to gold metal using liftoff and to a silicon substrate by reactive ion etching.

Room-temperature nanoimprint and nanotransfer printing using hydrogen silsequioxane

Room-temperature nanoimprint lithography (RT-NIL) technology has been developed to overcome critical dimensions and pattern placement errors caused by thermal expansion in the conventional nanoimprint lithography (NIL) process. We propose RT-NIL using hydrogen silsequioxane (HSQ) instead of the poly(methylmethacrylate) used in conventional NIL. We demonstrate HSQ-replicated patterns with a 90 nm diameter hole and 50 nm linewidth for room-temperature replications. Furthermore, we have developed new nanotransfer printing technology utilizing the adhesion characteristics of HSQ. We also demonstrate the transfer of photoresist and Au patterns from a mold to a substrate.

Nanomanipulator and actuator fabrication on glass capillary by focused-ion-beam-chemical vapor deposition

Three-dimensional (3D) nanostructures on a glass capillary have a number of useful applications such as manipulators, actuators, and sensors in the various microstructures. We observed a phenomenon that two diamondlike-carbon pillars on a tip of glass capillary fabricated by 30 keV Ga+ focused-ion-beam-chemical vapor deposition (FIB-CVD) with a precursor of phenanthrene vapor was able to work as a manipulator during FIB irradiation. It became clear that it was caused by electronic charge repulsion between two pillars, which accumulated electric charge by FIB irradiation. By applying this moving mechanism, we have developed a 3D nanomanipulator and actuator on a tip of glass capillary by FIB-CVD. Furthermore, in situ observations of movement for a 3D nanomanipulator and actuator have been demonstrated by applying voltage onto a Au-coated glass capillary.

Crystal growth of C60 thin films on layered substrates

The process of the C60 thin film crystal growth on layered materials such as MoS2 and mica is studied in detail with a combination of atomic force microscopy (AFM) and reflection high‐energy electron diffractometry, and is compared to that on alkali‐halide (NaCl) substrates. AFM shows that a single crystal containing triangle‐shaped grains of 1–2 μm size with a (111) surface terrace is grown on the MoS2 substrate over a large area through a layer‐by‐layer process, while the grains on mica are 200–400 nm in size and distribute with some disorder in the orientation. The epitaxial characteristics of the C60 crystal growth on these layered substrates are discussed in comparison with that on alkali‐halides.