Toshikazu Nosaka

Nanotweezers consisting of carbon nanotubes operating in an atomic force microscope

We have developed nanotweezers consisting of carbon nanotubes that will operate in an atomic force microscope. The two nanotubes were attached on the metal electrodes patterned on a conventional Si tip and their fixations were made by carbon deposition. These processes were made under the view of a scanning electron microscope. The application of a dc voltage to the two nanotube arms induces their movement to approach each other. The numerical simulation by taking into account the balance between the electrostatic attraction and the bending moment of the nanotubes well explains the motion of the nanotube arms.

Copper nitride thin films prepared by reactive radio-frequency magnetron sputtering

Abstract Copper nitride (Cu3N) thin films were deposited on glass substrates by reactive radio-frequency (rf) magnetron sputtering from a metal copper target in a nitrogen/argon atmosphere. The deposition rate of the films gradually decreased and excessive nitrogen was added to the films as nitrogen partial pressure increased. The color of the deposited films was a reddish dark brown. The Cu3N films obtained by this deposition method were strongly textured with crystal direction[100]. The grain size of the polycrystalline films ranged from 15 to 30 nm. The resistivity and the optical energy gap of the films were found to be change with the nitrogen content.

Rapid Growth of Vertically Aligned Carbon Nanotubes

100-?m-long vertically aligned multiwall carbon nanotubes were grown in 1 s. A thermal chemical vapor deposition method at 700?C was used with a catalyst of iron films and a carbon source gas of acetylene diluted with helium. This study revealed a novel rapid growth mode that appears in the beginning of chemical vapor deposition when the rate of increase in the concentration of carbon source gas is high at the substrate. This new growth mode, which precedes a normal growth mode, provides well-crystallized and straight nanotubes.

Effects of Ion Species on Reactive-Ion-Beam-Sputtered Zr–N Films

Thin films of Zr-N have been prepared by reactive ion-beam sputtering of a Zr target. Two kinds of ion species, Ar ions and nitrogen ions, were used for sputtering. The film structure, composition of film, and electrical and optical properties of Zr-N films were examined to compare the Zr-N films sputtered by nitrogen ion beam with those sputtered by Ar-ion beam in a nitrogen atmosphere. Semitransparent and highly resistive Zr-N films, which had different properties from stoichiometric ZrN films, were obtained when a Zr target was sputtered by a N-ion beam, whereas gold-colored Zr-N films, whose properties were similar to those of ZrN, were obtained by Ar-ion beam sputtering in a nitrogen atmosphere. It was found that the properties of the Zr-N films strongly depend on the ion species used for sputtering.

The use of the ion beam current as a process control in the reactive sputtering of zirconium oxide

Abstract A Zr target is sputtered in an oxygen atmosphere by a reactive-ion-beam-sputtering technique. It has been found that, even at a constant oxygen flow, the residual oxygen pressure during sputtering can be extensively controlled by the Ar ion beam current used for sputtering. The relationship between these factors is expressed quantitatively. The films composition, structure and optical properties are also transformed from a metallic to an insulating state by the Ar ion beam current. This indicates that the ion beam current used for sputtering can be used as a sputtering parameter for process control. In addition, it is demostrated that, by only controlling Ar ion beam current, the film composition is dynamically modulated towards the surface direction in a single sputtering process. This shows that the technique is applicable to optical film coating.

Structure of gold-hydrocarbon composite thin films deposited using low-voltage plasma sputtering method

We have investigated the properties of gold metal/polymer composite thin films. These composite films are prepared by DC plasma sputter deposition using an argon and methane gas mixture. A high-purity gold metal was used as a sputtering target. Sputtered gold atoms do not make compounds with hydrocarbon in plasma, because gold is a non-reactive metal. Additionally, both plasma polymerization of the methane and deposition of the sputtered gold atoms appear on the substrate. Consequently, composite films are formed. Composite films can be changed from metallic to dielectric according to the preparation conditions. There are main 2 parameters, i.e., the sputtering voltage and the partial pressure of the methane. It is necessary that the sputtering voltage is low, under 300 V in this work, because bombardment of the high-energy particles occurs to suppress the polymer growth on the substrate. It is found that the desired structure and properties of the composite thin films can be obtained, by suitable adjustments of the partial pressure of the methane, at a sputtering voltage of 300 V.

Preparation of Pd thin film photo-cathodes using ion-beam sputtering

Abstract We have proposed a new type of vacuum gauge using a palladium (Pd) thin film as a photo-cathode for measuring vacuum pressure. A photo-induced electron was adopted in place of the thermoelectron used in a conventional ionization gauge. The Pd thin film photo-cathode was prepared on a quartz substrate using the ion-beam sputtering method. It was irradiated by ultra violet (UV) light from a deuterium lamp. The photoelectron current emitted from the Pd thin film increased with decreasing film thickness. A maximum current of 240 nA was obtained from a film of 4 nm-thickness. It was found that the ionization gauge with the Pd photo-cathode at 7 nm thickness showed a linear response in the pressure range of 10 −2 -10 Pa in an Ar gas atmosphere. The photoelectric emission from the Pd surface by UV irradiation is affected by the sputtering conditions.

Deposition of ZrC thin films and plasma-polymerized hydrocarbon films in the reactive magnetron sputtering process

Abstract ZrC films are sputter deposited by r.f. magnetron sputtering using an acetylene reactive gas. The relationship between the film properties and sputtering conditions is investigated using reactive gas pressure and r.f. power as sputtering parameters. Two distinct kinds of deposition processes—sputtering from a target and polymerization from acetylene—occur during sputtering. The relative importance of these processes depends on the sputtering conditions. Furthermore, these processes strongly affect the film composition and properties. The mechanism of these processes during sputtering is clarified in order to obtain ZrC films with a high hardness. The application of r.f. power as a sputtering parameter to obtain suitable properties of ZrC films is also investigated.

Development of a low energy ion source with multicapillary anode

Abstract A new type of hot cathode ion source which has a multicapillary anode and a discharge stabilizer electrode has been developed. There are two special features in this ion source. The gaseous flow is intense and of the collimated beam type, because it is introduced through the multicapillary anode. A high ion current density ( > 5 mA/cm 2 ) can be obtained because discharge in high vacuum can continue with the help of the stabilizer electrode. At a stabilizer voltage ( V s ) of 50 V, ion current densities of 2.2 and 6.1 mA/cm 2 were obtained at acceleration voltages ( V acc ) of 20 and 200 V, respectively. The ion energy was dependent on V d , and the full width at half maximum (FWHM) of its distribution was less than 15 eV. Cu films were etched by this ion source. The etching rate ( E r ) was 150 A/min at V acc = 100 V. The relationship between the etching rate and V acc was represented by E r ∝ ( V acc ) α . The values of α were 2.0 in the region of V acc ≤ 100 V and 1.0 for V acc ≥ 100 V.