Takeo Nakano

Seikei University · Department of Materials and Life Science

In this study, an array of Mo cones for volcano-structured Spindt-type microelectron emitters were fabricated. A recently developed triode high power pulsed magnetron sputtering system was used to control the positive plasma potential and efficiently accelerate ion species. By applying a proper positive voltage to the additional electrode, the auth...

The growth of the target erosion profile (racetrack) in DC magnetron sputtering has been experimentally studied at a modest target power. Unbalanced magnetron sputtering (UBMS) and balanced magnetron sputtering (BMS) of a copper target were conducted at Ar gas pressures between 0.38 ∼ 2.0Pa at a constant DC discharge power of 100W. At time interval...

The incorporation of oxygen impurities under ambient environment conditions during reactive sputter deposition of titanium nitride (TiN) films has been studied. TiN films, prepared by DC sputtering of a Ti metal target in 100% N2 at 1 Pa in an ultra-high vacuum (UHV) sputtering apparatus, were essentially free from oxygen. When oxygen was intention...

The transport process of sputtered atoms has been studied experimentally through deposition rate measurement by changing the target-to-substrate (T-S) distance systematically along with the gas pressure and target element. The deposition rate showed power-law decay with the T-S distance, and the slope of the log-log plot became steep at a transitio...

Spindt-type emitters were fabricated with cavities made of Al/Mo/SiO2 using the triode high power pulsed magnetron sputtering method. We explored the process parameters (gas pressure and voltage of the additional cap electrode) to optimize the sharpness of the emitter shape. We found that the intermediate pressure and voltage were suited to obtain...

We prepared amorphous tungsten oxide films on indium-tin-oxide/glass substrates using reactive magnetron sputtering and investigated their electrochromic (EC) properties. To achieve the densely colored films, samples of 500 and 1000 nm thickness were deposited with different pumping speeds and oxygen flow rates at Ar 3 Pa atmosphere. The as-deposit...

Local structures of Ni species were studied in the NiO/γ-Al2O3 catalyst prepared by the impregnation method for the decomposition of dimethyl sulfide (DMS). Calcination and sulfurization conditions of the prepared catalyst affected the catalytic activity for DMS decomposition. The decomposition performance was increased with sulfurization by H2S co...

Human embryonic kidney 293T (HEK293T) cells are used in various biological experiments and researches. In this study, we investigated the effect of cell culture environments on morphological and functional properties of HEK293T cells. We used several kinds of dishes made of polystyrene or glass for cell culture, including three types of polystyrene...

High Power Impulse/Pulsed Magnetron Sputtering (HiPIMS/HPPMS) process has several interesting aspects and is vigorously studied in recent years. In this preface, some trends in HiPIMS research are briefly reviewed: 1) the applicability of HiPIMS to practical deposition processes, 2) the behavior of the transient and high density plasma, and 3) the...

High power pulsed magnetron sputtering (HPPMS) is a variant of sputtering deposition method in that pulsed power is applied to the sputtering target with low repetition frequency and small duty ratio. It produces high density plasma intermittently which enables the ionization of sputtered atoms and the control of their energy and direction by intro...

In this study, the effect of energetic species in sputter deposition of molybdenum films was studied using the triode HPPMS technique we developed recently. In triode HPPMS, the anode cap of the sputter gun is electrically insulated from the chamber ground and is applied a positive voltage (VC) to it. By this, the increase of plasma potential is ac...

The evolution of target “race track” erosion was evaluated experimentally during the conventional DC magnetron sputtering of metal targets with different Ar gas pressure environments. At gas pressures of 0.38, 0.5, and 1.0 Pa, an aluminum or copper target was sputtered at a DC discharge power of 100 W. At time intervals of several hours, the target...

A novel material for recovery and separation of precious metal using grape-derived waste has been developed. The material was fabricated glutaraldehyde-crosslinked polyphenol, which derived from grape-derived wastes. Adsorption performance of precious metals (Au, Pt, and Pd) onto glutaraldehyde-crosslinked polyphenol was investigated using inductiv...

We propose a method to obtain the pressure–distance product (pd) for thermalization in the sputtering process using a Monte Carlo (MC) simulation. Sputter-ejected atoms proceed forward with high energy, and fall into random motion finally. That is, after many MC trials the "average position" of atoms reaches saturation. The thermalization distance...

We have designed a new triode configuration in a magnetron sputtering apparatus to control the plasma potential of the discharge. An additional chimney electrode was introduced above the conventional sputter gun to apply a positive voltage. The discharge power was provided by a pulse power source to achieve high power pulsed magnetron sputtering op...

抄録 Discharge plasma, especially that generated at low gas pressures, is an important application of vacuum technology. This article describes the unique features of low gas pressure plasma, generation of plasma discharge and various plasma parameters. Plasma-wall interaction, which is very important for many plasma-related technologies, is also dis...

In this study, we investigated the effect of the target bias voltage during the pulse-off period in the pulsed magnetron sputtering (PMS) of repetition frequency 200 Hz and duty ratio 5–20%. Copper films were deposited by the PMS for Ar gas pressures of 1–5 Pa (with and without the pulse-off target voltage) and compared with those deposited by DC m...

We propose Spindt-type field emitter array fabrication process using the high power impulse magnetron sputtering (HiPIMS) deposition. HiPIMS method can get a lot of ionized sputtering particles due to high plasma density. We think that highly collimated film deposition may be realized by combining the potential control of the sputtering target and...

Films of vanadium oxide were prepared by reactive DC magnetron sputtering. Crystalline films of -V 2 O 5 could be obtained at 500°C for an hour in oxygen atmosphere. Further annealing made rod-like crystallites to grow, and optical spectra of transmittance and reflectance changed with annealing, but the change after the crystallization could be exp...

A new fabrication method of Spindt-type emitters will be presented. In our method, a double-layered photoresist is used as a parting layer, and high-power impulse magnetron sputtering is used instead of e-beam evaporator for emitter-cone formation. The etch-back method is adopted to form the multi-gate electrodes on each emitter cone.

With a high-power impulse magnetron sputtering (HiPIMS) apparatus, it has been studied how the target bias voltage during the off-pulse period affects the stability of the generated plasma. We have prepared an electrical pulse power source which can control the target voltage during the pulse off period, in addition to the pulse voltage, repetition...

The effect of the base pressure on the incorporation of oxygen into reactively magnetron-sputtered metal-nitride films has been investigated. A UHV sputtering system with a base pressure of less than 10−6Pa was used to examine the relationship between a deliberately introduced background pressure of oxygen and a measured oxygen content in the sputt...

The effect of background gas environment on the purity of reactively-deposited nitride films has been studied. Especially, the relation between the oxygen background pressure and its incorporation into the TiN film is investigated in this study. We have developed a UHV sputtering system and deposited TiN films under two different base pressure cond...

The mode transition of the DC reactive sputter deposition process has been studied for the fabrication and the stoichiometry control of SiOX films. At a fixed Ar flow rate of 20 sccm and a pressure of 1 Pa (hence the pumping speed was also fixed), oxygen flow rate was modified and the transition between the metal and oxide modes was monitored by th...

The ion-induced secondary electron emission (SEE) characteristics of sputter-deposited magnesium oxide (MgO) films have been investigated. Using an RF magnetron sputtering apparatus, MgO films of 50-200 nm thickness were deposited on Si substrates from a sintered MgO target. Under irradiation of 1 keV of Ar+ ions, secondary electrons were collected...

In sputter deposition processes, the thickness distribution of the film is affected by experimental conditions such as gas pressure, target–substrate (T–S) distance and target elements. To study these effects, we have designed a sample holder with three quartz crystal microbalance (QCM) thickness monitors on its surface and measured the distributio...

The island structure of indium has been investigated by employing the depth profile measurement of XPS. Indium films of 30˜180 nm (in mass thickness) were deposited on silicon substrate by vacuum evaporation at 80°C. The island structure was confirmed by AFM as the substrate surface was filled with islands. In an XPS apparatus, films were sputter-e...

The evolution of the surface morphology of Cu-In alloy film has been studied using an atomic force microscope. Samples of Cu-In were prepared by sequential vacuum deposition: copper was deposited to 10-40 nm thick first on a glass substrate, followed by the deposition of various amounts of indium to make the indium composition in the range of 0-75...

Magnesium oxide (MgO) films were prepared by RF sputter deposition technique, and their secondary electron emission (SEE) coefficient was examined in relation to film thickness and surface morphology. The optical constant and film thickness were evaluated from the optical transmission spectroscopy for samples prepared on the glass substrate. The io...

Optical emission from axisymmetric copper-sputter deposition plasma has been measured in a spatially resolved way, and the radial distribution profiles are obtained using a computed tomography technique. Among the emission spectrum two strong copper emissions at 324.8 and 510.6 nm are analyzed, because both emissions originate from the same excited...

The structural changes of sequentially evaporated thin Cu–In films on molybdenum substrate were studied by the depth profiling technique in an XPS apparatus. Pure metal materials were deposited by vacuum evaporation at room temperature. A specimen of the film was sputter-etched in situ after the deposition with Ar ion beams to obtain the depth prof...

The structural changes of sequentially evaporated thin Cu–In films on molybdenum substrate were studied by the depth profiling technique in an XPS apparatus. Pure metal materials were deposited by vacuum evaporation at room temperature. A specimen of the film was sputter-etched in situ after the deposition with Ar ion beams to obtain the depth prof...

The copper atomic density within the sputter plasma and its dependence on Target-Substrate (T-S) distance has been investigated using the optical emission spectroscopy (OES). It has been understood that the atomic density of copper can be evaluated from the intensity ratio of two emission lines at 510.6 nm and 324.8 nm both from Cu neutral. At high...

Transport process of sputtered atoms becomes more complex in mid-to-high pressure environment (2-20 Pa). At high pressures, sputtered atoms collide with ambient gas atoms frequently, and are ready to thermalize. We have been studying the situation with both Monte-Carlo (MC) computer simulation and experiment. We have extended the MC simulation in t...

A computer program has been developed to search for the optimum multi-layer filter structure by modifying the refractive indices (RI) of the layers continuously between 1.417 and 2.435, which are the RIs of SiO2 and TiO2, respectively. It aims to propose a design strategy where RI control of each layer is available by the recent progress in co-sput...

Scaling analysis of the surface roughness has been performed on copper films prepared by DC magnetron sputter deposition. The deposition was performed at Ar gas pressures of 2 and 10 Pa. Under both pressures, deposition rates were almost the same and were 1.1 nm/s. Self-affine parameters α and β were determined from a series of AFM topographs of fi...

Optical emission spectroscopy (OES) with a wavelength range of 185–525 nm has been performed for DC planar magnetron sputtering of copper in argon atmosphere. Spatial resolution of the light emission has been achieved by focusing the plasma image on one end of an optical fiber. The other end of the fiber is connected to a “polychromator” with linea...

A technique to determine optical constants of thin transparent films is discussed. Instead of the combination of the transmittance and the reflectance at a particular wavelength, the transmittance spectrum for a wider wavelength range is analyzed. The analysis is based on a fact that the dispersion of the complex refractive index n−ik of the film b...

The vibrational microscratch tester monitors electrically the frictional response of a scratch-stylus which is forced to oscillate on the film surface. This tester is so sensitive that it is able to detect the fracture of ceramic films less than 30 nm thick in situ by catching an irregular jump of the friction. The adhesive failure of films of duct...

Modeling of particle transports at high pressure sputtering has been studied. We assume that the diffusion process of thermalized particles is governed by the Poisson's equation, and this is solved by the boundary element method (BEM). The thermalization points are obtained by the Monte Carlo (MC) method using a ballistic approach, and they are tre...

Structural and electrical properties of the Cu–In binary system have been studied in thin films. Samples were prepared via sequential vacuum deposition and annealing. Copper of 10–40 nm thick was deposited on glass substrates first, and indium deposition was followed. The In thicknesses were chosen so as to make the atomic concentration of In 0–75%...

Transport properties of sputtered particles in a gas environment have been studied at finite temperatures using a recently developed new Monte-Carlo simulation code. In this code, the thermal motion of gas atoms has been incorporated to the collision frequency and the scattering process. The situation that the gas atoms are not frozen affects criti...

With the aim of developing new 1D platinum chain solids having infinite Pt−Pt bonds, several carboxylate-bridged cis-diammineplatinum dimers have been prepared and structurally characterized. For a dimer doubly bridged with acetates, five different salts [Pt2(NH3)4(μ-CH3CO2)2]X2·nH2O (X2, n = (ClO4)2, 2, 1; (NO3)2, 1, 2; (BF4)2, 4, 3; (PF6)2, 2, 4;...

The surface structure of {Cu, In} binary system on Si(111) has been studied with the low energy electron diffraction (LEED) technique. First, the quasi-‘5 × 5’-Cu structure can be prepared with the deposition of 1–2.5 ML of Cu on the clean surface of Si at temperatures of 300–550°C. With the additional deposition of 0.5-1.6 ML of In, the surface st...

A Monte Carlo simulation code has been developed to account for the mass transfer in the sputtering deposition. In the present work, the velocity of gas atoms at ambient temperature is taken into consideration, while the gas atoms have been regarded cold enough compared to the sputtered particle. The effect of gas motion becomes important at higher...

LaBx (x = 0–6) thin films were prepared by magnetron sputtering using a LaB6 target and Ar discharge gas. The composition of the films was investigated by the ICP method. It has been found that the composition strongly depended on the Ar discharge gas pressure. The film composition was mostly stoichiometric (x = 6) at low Ar pressures while the val...

Thin films of LaB 6 are prepared by a radio frequency (rf) magnetron sputtering technique. The effect of sputtering conditions on the film properties of internal stress and crystalline orientation are investigated. The film deposited at low pressures (≪1 Pa) has a strong compressive stress as high as 10⁹ Pa. As the pressure of Ar dischar...

LaB6 films from 2000 to 5000 Å thick were prepared on glass substrates by rf magnetron sputtering. The effects of Ar discharge gas pressure from 5.3 to 5.3 × 10-2 Pa on the structural, electrical and mechanical properties of the films were examined. The structural characteristics were analyzed by X-ray diffraction and emission spectrochemical techn...