Takeo Nakano

Local structures of Ni species were evaluated in the NiO/γ-Al2O3 catalyst prepared via impregnation method for dimethyl sulfide (DMS) decomposition. Calcination and sulfurization conditions of the prepared catalyst influenced by the catalytic activity for DMS decomposition. The decomposition performance increased with sulfurization by H2S compared to sulfurization with DMS prior to the reaction test. X-ray diffraction and X-ray photoelectron spectroscopy analyses suggested that the active sites are NiS. In-situ X-ray absorption spectroscopy analysis was performed to examine the fine structural changes in Ni species before and after the sulfurization treatment. At 500°C calcination of the catalyst, Ni species were present as NiO and NiAl24 at a ration of 4:6 and only NiO was sulfurized to NiS which acted as the active sites. Meanwhile, for the catalyst calcined at 800°C, Ni species were nearly completely present as the Ni component in the NiAl2O4 structure, which was less susceptible to sulfurization than NiO. This result implied that the NiS amount in the catalyst calcined at 800°C was greatly reduced, resulting in lower decomposition activity.

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 dishes provided from different manufacturers for suspension and adherent cell culture. In addition, we also investigated the effect of culturing on gelatin-coated surfaces on the cell morphology. We found that HEK293T cells aggregated and formed into three-dimensional (3-D) multicellular spheroids (MCS) when non-coated polystyrene dishes were used for suspension culture. In particular, the non-coated polystyrene dish from Sumitomo bakelite is the most remarkable characteristic for 3-D MCS among the polystyrene dishes. On the other hand, HEK293T cells hardly aggregated and formed 3-D MCS on gelatin-coated polystyrene dishes for suspension culture. HEK293T cells adhered on the non- or gelatin-coated polystyrene dish for adherent culture, but they did not form 3-D MCS. HEK293T cells also adhered to non- or gelatin-coated glass dishes and did not form 3-D MCS in serum-free medium. These results suggest that HEK293T cells cultured on non-coated polystyrene dish may be useful for the tool to analyze the characteristics of 3D-MCS.

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 intervals of several hours throughout the target life, the target was removed from the chamber, and its erosion profile was measured with a height gauge. The racetrack width was found to have an interesting pressure dependence. Higher argon gas pressure resulted in a wider initial track width in both the UBMS and BMS configurations. As the sputter erosion of the target proceeded, the track width became narrower at higher gas pressures (>1.0Pa). At lower gas pressures, the track width was mostly unchanged and even showed a slight increase in the case of 0.38Pa in UBMS. As a result, the order of the final width was reversed: the higher gas pressure resulted in a narrower track width. The origin of this behavior was ascribed to the difference in the plasma sheath thickness and the free path of secondary electrons. (C) 2016 Elsevier B.V. All rights reserved.

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 authors obtained good cone shapes with high aspect ratios in a water-cooled microcavity structure made of two resist layers, which was previously impossible by conventional vacuum evaporation techniques. The effects of ion acceleration on the alignment of ions along the normal direction, as well as on the stress in the deposited film, are discussed. The former is important for the formation of sharp cones, while the latter is crucial for achieving stable fabrication. (C) 2017 American Vacuum Society.

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 inductively coupled plasma atomic emission spectrometry. Commercially available material was adsorbed regardless of the type of the precious metal however, glutaraldehyde-crosslinked polyphenol selectively absorbed Au. Glutaraldehyde-crosslinked polyphenol can be deposited as precious metal in the form of metal without reductants. These results indicate that glutaraldehyde-crosslinked polyphenol has great potential for separating and recovering materials, such as in urban mining and in plating waste.

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 was taken out of the chamber and its erosion profile was measured with a height gauge. As the sputtering erosion of the target proceeded, the erosion track diameter was almost the same in all sputtering conditions, whereas the track width (full width at half maximum: FWHM) showed quite different behaviors depending on the gas pressure. At 0.38 Pa, the FWMH increased slightly with increasing sputtering time. On the other hand, at 1.0 Pa, the FWMH decreased with increasing sputtering time.

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 d can be estimated from this saturation position. We could obtain the pd product for Al, Cu, and Mo in argon atmosphere. The pd values agreed well with the pressure dependence of the deposition profile observed experimentally. © 2014 The Japan Society of Applied Physics.

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 transition pressure. The transition pressure decreased as the mass of the sputtered atoms decreased, which suggested that the transition was related to the transport of the sputtered atoms and their thermalization. Two separated thickness monitors showed that the thickness uniformity was worsened by the thermalization.

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 operation. We confirmed that the plasma potential increased with increasing positive electrode voltage. Copper films with substantially flatter surfaces could be obtained on a water-cooled and electrically grounded substrate at an Ar gas pressure of 5 Pa. © 2014 The Japan Society of Applied Physics.

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 intentionally introduced into the vacuum chamber, an impurity level of a few atomic percent was obtained at a partial pressure of 3×10-4 Pa, but the percentage increased rapidly to 10-20 at. % when the partial pressure was 1×10-3 Pa or above. It is shown that the increase in the oxygen incorporation is not well explained by the oxygen impingement rate calculated from the partial pressure. We demonstrate that the impurity concentration is related to the ratio of the number of oxygen atoms introduced into the chamber to the number of Ti atoms sputtered from the target. This suggests that oxygen gettering by Ti atoms deposited on the chamber wall significantly reduces the oxygen pressure during deposition and that oxygen incorporation in the film is governed primarily by the total amount of sputtered metal.

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 magnetron sputtering (dcMS). The time-averaged power was set to 100 W. Compared to films deposited by dcMS, those deposited by PMS showed smooth surface and a ductile nature. These properties became more evident when the positive pulse-off voltage was applied. To clarify the reason for film structure modification, the plasma was investigated by time resolved Langmuir probe measurement. It was confirmed that electron density was as high as 10(17) m(-3) in PMS mode during the pulse-on period. On applying +40 V of pulse-off target voltage, the plasma potential was found to be raised by about 30 V in comparison to the zero voltage case. We suggest that this increase in the plasma potential leads to an increase in impinging energy of Cu ions on the substrate, and modifies the deposited film structure. Though the pulsed plasma we used was in the modest power range, we expect this approach is applicable to high-power impulse sputtering (HiPIMS) mode with high degree of ionization. (C) 2012 Elsevier Ltd. All rights reserved.

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 HiPIMS method. We tried that molybdenum deposition in a gatehole structure using potential-controlled HiPIMS method. And, we demonstrated that the possibility of the FEA fabrication process using this method. © 2012 IEEE.

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 frequency and a duty ratio of the pulse. Time-resolved current-voltage characteristic was monitored by an oscilloscope, and plasma generation behavior was elucidated. With titanium target and at Ar gas pressures of 0.6-5 Pa, pulse-off bias voltage was changed between -300 and +100 V, and the I-V characteristics were recorded. On increasing the negative bias voltage, the time at which the target current began to rise was gradually delayed. And at a certain voltage, the delay suddenly disappeared. This voltage was found to be the sustain voltage of the dc discharge in the same condition. Applying positive bias voltage resulted in a much longer delay. These results suggest that the minimal discharge during the pulse-off period helps the initiation of high-density plasma, while the bias voltage which can not maintain the plasma contrarily hampers it. (C) 2010 Elsevier Ltd. All rights reserved.

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(-6) Pa was used to examine the relationship between a deliberately introduced background pressure of oxygen and a measured oxygen content in the sputter-deposited TiN films. The results showed that with an oxygen partial pressure of 10(-4) Pa, the deposited TiN was found to include 10-20 at.% of oxygen when measured by the technique of X-ray photoelectron spectroscopy (XPS). When no oxygen was admitted into the system, no trace of oxygen could be detected in the deposited TiN films. The incorporation mechanism is discussed in terms of the coverage-dependent sticking probabilities of O(2) and N(2) on a Ti metal surface. (C) 2008 Published by Elsevier Ltd.

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 conditions: one was a UHV condition less than 10 -6 Pa, and the other was 1 ×10 -4 Pa of oxygen. The oxygen content of the films was examined with X-ray photoelectron spectroscopy. While no trace of oxygen was detected in the TiN film deposited under the UHV condition, 10 at.% of oxygen was observed in that deposited with the O 2 introduction. The extent of O 2 incorporation into the TiN film is discussed based on the difference in sticking characteristics of oxygen and nitrogen on the titanium surface.

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 50-200nm thickness were deposited on Si substrates from a sintered MgO target. Under irradiation of 1 keV of Ar+ ions, secondary electrons were collected at a positively biased electrode. The secondary electron current increased as the bias voltage increased, and saturated to give an SEE coefficient of 2-2.5 in all samples. The deposition condition (gas pressure 2-20Pa) did not strongly affect this current-voltage (I-V) characteristic of the SEE, while an increase in film thickness resulted in an increase in the voltage at which the SEE current began to rise. This rising voltage depended neither on the energy nor on the current of the primary ion beam. We concluded that the rising voltage was governed by an electric breakdown phenomenon by which the positive charge accumulating on the surface was compensated from the substrate. The field strength was estimated to be as high as 10(9) V/m.

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 distribution of the depositing flux around the sample holder, including the circumvented deposition onto the back face. As for the gas pressure dependence for a T-S distance of about 50 mm, the relative deposition flux on the back face was found to be at its maximum at pressures of 1-2Pa. Above this pressure, the uniformity of the flux on the front face became gradually worse. The observed characteristics could be reproduced by a Monte-Carlo simulation of the particle transport process. The reduction of the circumvented deposition and the uniformity degradation at high gas pressures were ascribed to the start of thermalization of sputtered particles and the shrinkage of its spatial profile toward the target. (c) 2005 Elsevier Ltd. All rights reserved.

The mode transition of the DC reactive sputter deposition process has been studied for the fabrication and the stoichiometry control of SiO x 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 the cathode voltage. With a constant current operation of a DC power source, well known steep and hysteretic mode transition appeared. On the other hand, gentler transition with no hysteretic character was observed in a constant power operation. In the latter case, the dependence of the deposited film composition on the oxygen gas flow rate was examined by X-ray photoelectron spectroscopy. The increase in the film composition x from 0.5 to 2.0 was observed in a smaller flow rate region compared to the process mode transition. It can be attributed to the non-uniform deposition of Si atoms which work as oxygen absorber.

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 10-40nm 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 at.%. Samples were prepared under three different conditions: A) deposited at room temperature (RT); B) deposited at RT and annealed at 120 degrees C in vacuo; and C) deposited at 120 degrees C. Samples formed by A and B (series A and B) showed a growth with a dynamical exponent beta of similar to 0.3 while the atomic ratio In/Cu was less than 2. The formation of CuIn(2) intermetallic compound was observed by X-ray diffraction as the atomic ratio approached 2. After that, beta suddenly increased to similar to 0.7, which was attributed to the segregation of excess indium atoms to form cap-shaped islands. For samples grown by C (series C), the roughness initially increased more rapidly with beta similar to 0.7 and decreased above In/Cu similar to 1. It showed a minimum at In/Cu = 2 and finally increased again with beta similar to 0.7 by forming indium islands, as in series A and B.

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-etched with Ar ion to obtain the depth profile. On plotting the XPS signals of In and Si against the sputter time normalized by the deposited amount, the depth profiles of films of various thicknesses were found to have a curve in common. We can explain this universal relation by a model in which the islands of the same form completely cover the substrate surface, and shrink as they are sputtered keeping their similarity. The agreement of the experimental result with our model also suggests that the In islands do not change their form during the growth.

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 state, so their intensity ratio reflects the spatial density of ambient copper atoms. As gas pressure and/or discharge power were increased, the decrease in the relative intensity of the 324.8 nm emission was observed experimentally. The density of copper atoms in the plasma is discussed with the optical absorption and the re-emission being taken into consideration. (C) 2004 Elsevier Ltd. All rights reserved.

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 profile. Another specimen of the film was annealed at 120degreesC for 1 h, and the depth profile was taken. The transient characteristics of signal appearance/disappearance of elements of film/substrate were different before-and-after the annealing. The behavior was discussed based on the film structure whether it was in a layered form or in an island form. It was suggested that the observed profiles for films prior to the annealing could be explained as a layered one, but they became island-like structure of alloys after the annealing. Films of various indium composition were also examined. The tendency of island formation was stronger for films with higher indium content. On films whose In composition was more than 70%, indium islands were also formed. (C) 2004 Elsevier Ltd. All rights reserved.

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 ion-induced SEE coefficient was measured for MgO films deposited on Si substrates of both mirror-polished (root mean square (RMS) roughness < 1 nm) and etched-rough (RMS roughness similar to 40 nm) faces, in an XPS apparatus using the primary ion beam of Ar+ at 1 keV. The SEE coefficient was as large as 2.5 for 100 nm MgO films, and did not depend strongly on the process pressure nor the roughness of the silicon substrate. Samples of 200 nm MgO thickness showed a current instability in the SEE measurement, probably due to the charge up. (C) 2004 Elsevier Ltd. All rights reserved.

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 atomic density environment, the intensity ratio I510/I324 becomes larger because the 324.8 nm emission is absorbed by the environmental copper atoms at ground state. In this study, we changed the T-S distance within 35-75 mm, and measured the optical emission from the side along the line fixed at 1 cm away from the target surface. At pressures larger than 5 Pa, the intensity ratio increased by increasing the T-S distance, which denoted the increase of atomic density between the target and the substrate holder. It should originate from the diffusion-like atomic transport in which the substrate holder worked as the absorbing boundary.

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 films deposited for various periods (30∼180 min). At 10 Pa, the roughness parameter α was 0.6∼0.7 and the dynamical parameter β and 0.9, while at 2 Pa, where the surface roughness grew more modestly, α was 0.5∼0.7 and β was 0.6. The difference also appeared in the correlation length ξ. The correlation length became larger as the deposition proceeded at 10 Pa, in accordance with the roughness evolution theory. On the other hand, it stayed almost constant at 2 Pa. The effect of gas pressure on the surface roughness is discussed.

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 linear CCD array sensors, which enables an uptake of whole spectrum simultaneously. Several emission lines from Cu neutrals, Ar neutrals and Ar ions have been identified in the observed wavelength range. In this study, the emission spectra were measured at positions of 5 and 10 mm above the center of the Cu target. Dependences of emission intensities on discharge pressure and power have been studied, and the excitation process of Cu radicals is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.

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 body can be described well with four parameters in the Lorentz theory. The surface roughness and the film thickness are also taken as fitting parameters, and hence the optical behavior of the film can be calculated with these six parameters. A set of best parameters is determined so that the square sum of the difference between the calculated transmittance and the observed one over the visible spectral range can be minimized. MgO films were prepared on glass substrates by the rf magnetron sputtering from a MgO target. The sputtering was carried out in the mixture gas of Ar and O-2 at 1 Pa. Fairly transparent films of various thickness (< 0.25 <mu>m) could be prepared. The transmittance spectrum was analyzed and the six parameters were determined. The parameters were found to be almost the same in all samples except the thickness and the roughness. The refractive index was 1.72 +/- 0.01 and the extinction coefficient was less than 3 x 10(-4) at the wavelength of 633 nm. The parameter of the surface roughness agreed well with the roughness value which was measured using the atomic force microscope. (C) 2000 Elsevier Science Ltd. All rights reserved.

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 mm thick in situ by catching an irregular jump of the friction. The adhesive failure of films of ductile materials, however, does not necessarily yield a sufficient fracture signal. In the present study, the waveform of the frictional signal for an oscillation period is decomposed into the frequency regime by Fourier expansion. The signal due to the solid friction is found to appear only in odd harmonics of the fundamental excitation frequency. By integrating the component of even harmonics of the observed signal, the critical failure of the adhesion has been made to observe more sensitively. The observation of the critical failure of thin copper films is demonstrated. (C) 1999 Published by Elsevier Science B.V. All lights reserved.

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 treated as the source of particles in the Poisson's equation, The result of BEM agrees fairly well with MC for the diffusion of low-energy particles under high pressures, while the computation time is extremely reduced. The hybrid method-MC and BEM, before and after the thermalization-has also been developed, and the comparison with experiments is shown. © 1999 Elsevier Science S.A. All rights reserved.

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 critically on the transport process of particles of low energies since the effect of the thermal motion of the colliding gas atom becomes important on the change in speed and direction with scattering. in this report we show the time evolution of position and energy of sputtered particles. The manner how the mass difference of sputtered particles works is demonstrated graphically. (C) 1998 Elsevier Science Ltd All rights reserved.

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%. Physical properties became stable after annealing at 120 degrees C for 10 min. The X-ray diffraction pattern of the alloy film exhibited the C16 structure near the 65 at.% In, suggesting the formation of the intermetallic compound CuIn2. Electrical properties of films were evaluated with Hall measurement. The resistivity of the ahoy film increased with In concentration, had a maximum at similar to 35 at.%, then decreased and showed a minimum at similar to 65 at.%, reflecting the CuIn2 formation. Hall coefficient of alloy films was naturally negative at low concentrations of In. However, the value gradually decreased to zero with the increase in In content and finally became positive above 40-50 at.% of In. From the temperature dependence of these electrical properties in the alloyed films, the co-existence of the 'hole'-like and 'electron'-Iike electron orbits has been speculated. (C) 1998 Elsevier Science S.A. All rights reserved.

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 [Pt-2(NH3)(4)(mu-CH3CO2)(2)]X-2. nH(2)O (X-2, n = (ClO4)(2), 2, 1; (NO3)(2), 1, 2; (BF4)(2), 4, 3; (PF6)(2), 2, 4; (SiF6), 4, 5) have been prepared. The crystal structure of 5 has revealed that an infinite dimer chain [Pt-2(NH3)(4)(mu-CH3CO2)(2)](n)(2n+) can be given as a result of hydrogen bond formation between the ammines and the oxygen atoms of acetates, demonstrating our prediction that the N2O2 coordination sphere may serve as a hydrogen-bonding moiety to assist formation of an infinite dimer chain. An asymmetric dimer bridged by both acetate and hydroxide ligands, [Pt-2(NH3)(4)(mu-CH3CO2)(mu-OH)](SiF6) (6), has also been isolated as a byproduct of 5, and a similar 1D framework, [Pt-2(NH3)(4)(mu-CH3CO2)(mu-OH)](n)(2n+), has been characterized by X-ray diffraction. In addition, some glycolate-bridged analogues of similar frameworks have been synthesized and characterized: [Pt-2(NH3)(4)(mu-CH2(OH)CO2)(2)](SiF6). 4H(2)O (7), [Pt-2(NH3)(4)(mu-CH2-(OH)CO2)(2)] (ClO4)(2). H2O (8), and [Pt-2(NH3)(4)(mu-CH2(OH)CO2)(mu-OH)](NO3)(2) (9) To obtain partially oxidized systems, benzoate derivatives have been selected as bridging ligands. Although a benzoate system gave dark blue solids ascribable to mixed-valence Pt(2.25+) compounds, a crystallographically analyzed complex has turned out to be a double complex involving both a Pt(II) monomer and a dinuclear Pt(II) complex, [Pt-2(NH3)(4)(mu-C6H5CO2)(2)](2)(SiF6) (BF4)(2).[cis-Pt(NH3)(2)(C6H5CO2)(2)]. 3H(2)O (10). Nevertheless, our final efforts in this work have revealed that a p-hydroxybenzoate system, [Pt(2.25+)(2)(NH3)(4)(mu-p-C6H4(OH) CO2)(2)](2)X-5. nH(2)O (X-5, n = (SO4)(2.25)(p-C6H4(OH)CO2)(0.5), 5, 12a; (PF6)(2)(SO4)(p-C6H4(OH)CO2), 6, 12b; (PF6)(2)(NO3)(2)(p-C6H4(OH)CO2), 7, 12c), may be suited to achieve a 1D platinum blue system. The compounds display a blue chromophore at 630 nm ascribable to the Pt(2.25+)(4) species. Moreover, the compounds have been judged to be diamagnetic, and therefore the S = 1/2 spins derived from the Pt(2.25+)(4) units must be diamagnetically coupled in the solid state, suggesting that the repeating unit should be expressed as [Pt(2.25+)(8)](n) (n is undetermined).

The surface structure of (Cu, In) binary system on Si(lll) has been studied with the low energy electron diffraction (LEED) technique. First, the quasi- '5 X 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 degrees C. With the additional deposition of 0.5-1.6 ML of In, the surface structure changes into a 4 X 1 structure at temperatures between 400 and 500 degrees C. At 550 degrees C, however, the '5 X 5'-Cu structure does not disappear, despite of the supply of In vapor.

A Monte Carlo simulation code has been developed to account fur 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 pressures since sputtered particles tend to be scattered more frequently and to be decelerated more. We present the formalism of (1) mean free path of the sputtered particle, (2) velocity distribution of the colliding gas particle, and (3) transformation of the coordinates between colliding system and laboratory one, The effect of these processes on the compositional deviation of LaB6 films that are sputter-deposited at higher gas pressures is discussed.

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 value of x decreased with increasing pressure. This nonstoichiometry is interpreted in terms of collision scattering of sputtered particles from the target by Monte Carlo simulation. The Ar pressure change induces the change of the crystal orientation of the films and this change is related with the work function of the film. The most appropriate Ar pressure for the preparation of the films used as electrodes is discussed. © 1993.

Thin films of LaB6 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 10(9) Pa. As the pressure of Ar discharge gas decreases, the internal stress becomes greater and the preferred orientation is transformed in the sequence: (100) --> (110) --> (111). This behavior can be explained as an energetically favorable structure of LaB6 film by taking both the surface energy and the strain energy into account. An application of a negative bias (- 20 V) to substrates results in a greater stress, so that the (110) and (111) orientation becomes more preferential.