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To clarify the mechanism of the decline in oxidative stress tolerance of leaves during the course of senescence, we studied the differences in the levels of various antioxidants and antioxidant enzymes in leaves of different ages. In 8-week-old tobacco plants, even though the chlorophyll content had not changed, the protein content and the photosynthetic capacity were significantly decreased in the older leaves compared to the younger leaves. The older leaves had constitutively higher levels of H 2 O 2 . Analyses of the components of the active oxygen species-scavenging system revealed that older leaves had significantly lower levels of ascorbate, glutathione and most of the antioxidant enzymes, especially catalase, Cu/Zn-superoxide dismutase, and ascorbate peroxidase (APX). When leaves of different ages were treated with 0.5 μM methylviologen under moderate light intensity at 150 μmol photons m −2 s −1 , the older leaves lost more chlorophyll and sustained ion leakage. During the induced photooxidative stress, chloroplastic APX, a key component of the water–water cycle, was particularly destroyed in the older leaves. These findings suggest that the decline in the levels of antioxidants and antioxidant enzymes associated with leaf senescence lead to lower photooxidative-stress tolerance, which might in turn accelerate the propagation of senescence.

Plasma Immersion Ion Implantation (PIII) has been developed as a method for high-flux implantation and conformal implantation on a complex shaped target. In PIII, a negative pulsed high voltage is applied to the target immersed in low-pressure high-density plasma. Then an ion sheath is formed around the target and energetic ions are implanted on the target surface. By increasing the plasma density, conformal implantation is possible. However, this process can not be easily realized for a complex shaped target, for instance which has a trench or holes with high aspectratios. In order to find the best condition in the process, it is very important to know the sheath shape around the target and the energy and flux distributions of implanted ions at each surface point. Plasma behavior in the PIII process has been simulated using “PEGASUS”.

Transgenic tobacco plants expressing a cyanobacterial fructose-1,6/sedoheptulose-1,7-bisphosphatase targeted to chloroplasts show enhanced photosynthetic efficiency and growth characteristics under atmospheric conditions (360 p.p.m. CO2). Compared with wild-type tobacco, final dry matter and photosynthetic CO2 fixation of the transgenic plants were 1.5-fold and 1.24-fold higher, respectively. Transgenic tobacco also showed a 1.2-fold increase in initial activity of ribulose 1,5 bisphosphate carboxylase/oxygenase (Rubisco) compared with wild-type plants. Levels of intermediates in the Calvin cycle and the accumulation of carbohydrates were also higher than those in wild-type plants. This is the first report in which expression of a single plastid-targeted enzyme has been shown to improve carbon fixation and growth in transgenic plants.

Depth dependence of ion beam induced epitaxial crystallization in Si has been studied to investigate the diffusion of defects responsible for crystallization. Regrowth rates for 3 MeV Au, 3 MeV Si and 5 MeV Au were measured by ion channeling for different depths. Decreases in regrowth rates were clearly observed near the surface (

The microstructure of silica glasses which have been implanted with 1.0 MeV O and 1.8 MeV Cu ions and subsequently annealed at 1000°C are examined by transmission electron microscopy (TEM). It is found that a high density of single crystal nanoparticles are formed in a buried layer around 0.8–1.7 μm in depth. In the case of the Cu-implanted sample, only single crystal Cu nanoparticles are observed. When the ratio of the implanted O to Cu ion is 0.5:1, single crystalline nanoparticles of Cu2O are observed at a deeper part of the buried layer, associated with the projected range of the implanted O ions. As the O ion dose increases up to a ratio of O to Cu like 1:1, single crystals of CuO are formed in the buried layer. The depth profile of Cu and the size distribution of the nanoparticles are affected by the O ion-implantation.

By plasma-based ion implantation (PBII) such as low-energy ion beam implantation in plasma, ion beam assisted deposition, and plasma immersed ion implantation, a diamond-like carbon (DLC) film is synthesized. The structure of the DLC film can be characterized by the hydrogen concentration and the relative fractions of sp2- and sp3-bonded carbon. The energy of the impinging ion plays a crucial role for the film structure and thereby the mechanical, electrical and optical properties of the film. Dynamic Monte Carlo simulations with the binary collision approximation have been applied to the synthesis of DLC films by PBII. It was assumed that energetic CH3+ ions and CH3 radicals are incident on the surface alternately. The incident molecular ions dissociated into its individual atoms when colliding with the surface. The radicals adsorbed on the surface are dissociated by the binary collisions with the impinged atoms and a part of hydrogen atoms are released from the surface. It is assumed that only the atoms receiving enough energy to overcome the surface barrier enter the solid. Release of the displaced hydrogen atoms after the subsequent collision cascade is also assumed. The relative fraction of carbon atoms in the sp2 and sp3 state were estimated by setting different displacement threshold energy for each state. Effects of the ion/neutral arrival ratio and the ion energy on the deposition rate and on the depth profile of the hydrogen content and the sp3/sp2 ratio in the deposited film are presented.

Titanium dioxide (TiO 2 ) films prepared by a sol-gel method were irradiated with 0.5 MeV V, Ti and 1.8 MeV Au ions and subsequently annealed at approximately 480°C. After the implantation and thermal annealing, the microstructure and the optical properties of the TiO 2 films were studied by Rutherford backscattering spectrometry (RBS), optical absorption and glancing angle X-ray diffraction measurements. It was found that the distribution of the implanted metal was slightly changed after annealing. The absorption edge of the films also slightly shifted toward the longer wavelength side. The films were composed of anatase and rutile phases. The anatase phase was reduced by ion implantation.

We have examined the change of electric conduction of silicon nitride induced by MeV Si ion implantation. 2 MeV Si + ions were implanted at the doses from 1×10 14 to 3×10 17 ions/cm 2 in 12 steps, by measuring the resistance using dc-constant voltage method between two deposited Mo thin films as electrodes on the sample. Temperature during implantation was 370–530 or 600 K without or with heater. Up to the dose of 2×10 16 or 8×10 15 ions/cm 2 for without or with heater, sheet resistance was larger than 10 9 Ω/□. The resistance decreased dramatically with increasing dose and it became less than 10 5 Ω/□ at doses over 1×10 17 ions/cm 2 . Saturation of conductivity over the dose of 1×10 17 ions/cm 2 was clear with the heater. Temperature dependence of conductivity indicates that the conductor is as semiconductor. After annealing up to 1000 K, the conductivity increased; however, it decreased beyond 1150 K and it became almost non-conductive at 1500 K. The electric conduction induced by Si ion implantation occurs via a variable-range hopping process and closely related to defects and their behavior.

The structure of a diamond-like carbon (DLC) film synthesized by ion-assisted deposition can be characterized by the hydrogen concentration and the relative fraction of sp 2 bonded carbon and sp 3 bonded carbon. Substrate bias, i.e. the energy of the impinging ion, plays a crucial role for the film structure and thereby the mechanical, electrical and optical properties of the film. Dynamic-Monte Carlo simulations with the binary collision approximation have been applied to the synthesis of DLC films by ion beam-assisted deposition. In the model, energetic CH 3 + ions and CH 3 radicals are incident on the surface alternately, and for the radicals on the surface, it is assumed that only the atoms receiving enough energy to overcome the surface barrier enter the solid. We assumed (a) a unity and only one monolayer sticking of CH 3 radicals on the surface; (b) the incorporation of H and C atoms into the bulk by binary collisions with energetic CH 3 + ions; (c) the release of H atoms by the dissociation of CH 3 radicals on the surface; and (d) the complete dissociation of CH 3 + ions into one C atom and three H atoms with identical velocities upon bombarding the surface. In addition to the above assumptions, (e) release of the displaced H atoms after the subsequent collision cascade is also assumed. The model takes into account full collision cascade induced by the impinged atoms and the changes of cross-sections of nuclear and electronic collisions induced by the accumulation of atoms and damage. Results are presented for the dependence of H concentration and of the deposition rate on the threshold displacement energy of H, the dissociation energy of CH 3 , the trapping rate of displaced H atoms, and the ion/neutral arrival ratio and the ion energy.

Recently a pulsed inductively coupled plasma source suitable for plasma-based ion implantation has been developed. The use of a pulsed plasma for plasma source ion implantation (PSII) processing takes advantage of the fact that a high-density plasma can be obtained with low average power because of the shortening of the plasma ignition time. A time resolved plasma density and the spatial profiles of the pulsed inductive RF plasma for the PSII method were measured. Under the optimal condition of the pulsed plasma, DLC thin films were successfully deposited on silicon substrates using Ar, CH 4 and C 7 H 8 gases, and the effects of the implantation voltage on the hydrogen concentration and the deposition rate of DLC coating were measured in the range of 5–20 kV. It was found that the deposition rate decreased with increasing implantation voltage and the hydrogen concentration was within 15–22 at.%.

In order to study the behavior of implanted nitrogen into Zr/carbon and Si/carbon bilayers, depth profiles of 15N and 14N were measured using the nuclear reaction of 15N(p,αγ)12C and 14N(3He,α)13N, respectively. The measured depth profiles were compared with the calculated profiles obtained by Monte Carlo simulation using dynamic-SASAMAL assuming a 25 at.% saturation for nitrogen concentration in carbon. Single 15N implantation and alternate implantation of 15N and 14N were performed at RT and at 700°C, with and without annealing. For depth profiling of the other elements, RBS was used and the chemical state was analyzed by XPS with Ar sputtering. The depth profiles of implanted nitrogen in Zr (60 nm)/glassy carbon (GC) showed nitrogen diffusion from the GC layer to the upper Zr layer. The depth profiles of the implanted nitrogen in Si/GC and Si/diamond-like carbon (DLC) agreed with the SASAMAL results assuming 40 at.% saturation for N in Si. The depth profile of 15N (1 × 1017 cm−2) which was implanted into Si/DLC after 14N (4 × 1017 cm−2) implantation did not agree with the calculated result but were almost the same as the profiles of 14N (4 × 1017 cm−2) except for the concentration level. And half of the 15N were lost during the annealing at 700°C, 1 h, keeping the same depth profile. The annealing behavior of the first implanted 14N was the same as the 15N.

Efforts have been dedicated to the formation of carbon nitride, a super-hard material, by many researchers. However, the nitrogen to carbon ratio obtained by high dose nitrogen implantation into carbon is quite limited by nitrogen diffusion towards the surface during the implantation. In order to study the behavior of implanted nitrogen, dynamic Monte Carlo simulations were carried out using the dynamic-SASAMAL code for nitrogen implantation into carbon, Si/C and Zr/C bilayers with energies of 25, 50 and 150 keV at doses of 5 × 1016 to 1018 cm−2. The calculated results were compared with the experimental results obtained by NRA, RBS, and XPS for RT implantation with and without annealing, and for 700°C implantation. For the RT implantation at a low fluence up to 1 × 1017 ions/cm−2, the measured NRA profile agreed well with the calculated result and almost all implanted nitrogen retained in the target. But diffusion began around 2 × 1017 cm−2 and the maximum concentration did not reach the calculated value. And the nitrogen concentration saturated at 25 at.%, and retained doses were much lower than the calculated values in all systems. The atomic ion mixing and the sputtered losses obtained by the calculation and the experiment were agreed very well.

Microstructure of the titanium hydride (deutende) films prepared by rf reactive sputtering with Ar and H2 (or D2) gases were examined by X-ray diffraction measurements, scanning electron microscopy, Rutherford backscattering spectrometry and elastic recoil detection analysis. In addition, their optical measurements were also carried out in visible and infra-red regions. It was found that the hep Ti structure (α-TiHx) was mainly formed at high rf power. With decreasing rf power, however, the fcc CaF2 structure (δ-TiHx) was obtained. The films have a smooth surface at a short time of deposition for 1–10 min, and these films are used for optical measurements. The films show wide absorption over visible and infra-red regions, although the films include a large amount of O atoms, which may suggest the presence of the amorphous titanium oxide phase.

Diamond-like carbon (DLC) films prepared by an ion plating method using C 6 H 6 plasma were implanted with 25 keV nitrogen 15 N ions to a total dose of 5 × 10 17 ions/cm 2 at temperatures up to 900°C. The atomic concentration of the implanted layer was measured by nuclear reaction analysis (NRA) and elastic recoil detection (ERD). Macro- and micro-tribological properties of the implanted layer were examined by a reciprocating tribotester and atomic force microscope (AFM), respectively. It was found that the nitrogen concentration in DLC films implanted at RT saturated at 23%, and a groove was formed by micro-wear on the surface at a low load of 150 nN, whereas the groove was not formed on the unimplanted surface. At 900°C implantation, the maximum concentration of nitrogen was 10%, and nitrogen implanted at high dose diffused into the substrate.

Silicon carbide was implanted with 50 keV nitrogen at elevated temperature up to 1100°C in order to form a composite of SiC and Si 3 N 4 . The depth profiles, the chemical state of the elements and the structure of the implanted surface were measured using Rutherford backscattering (RBS), nuclear resonance analysis (NRA), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and glancing angle X-ray diffraction (G-XRD). With increasing nitrogen fluence a replacement of carbon by nitrogen took place and β-Si 3 N 4 crystallites were formed on β-SiC surface at 1100°C, and the maximum concentration and halfwidth of the nitrogen profile implanted at 1100°C decreased in comparison with those implanted at

For nitrogen implantation into several kinds of metals (Al, Ti, V, Fe, Co, Ni, Zr, Nb, Mo, Ta, Hf, W) with a dose up to 2×10 18 ions cm −2 , dose dependence of the nitrogen depth profile, retained nitrogen dose and sputtering yield were calculated by Monte Carlo simulation using the dynamic SASAMAL code for the energy rage of 1 keV to 1 MeV. The calculated results were compared with the experimental results obtained by a resonant nuclear reaction analysis using 15 N(p, αγ ) 12 C reaction. In the simulation, it was assumed that the nitrogen concentration could not exceed that of saturated nitride phase and that the excess nitrogen migrated towards the surface depending on the radiation damage. The depth dependence of the chemical state measured by XPS and the crystalline structure of the surface layer obtained by a glancing angle XRD are also presented for Zr implanted with 50 keV nitrogen at room temperature and at high temperature or with post implantation annealing. The depth dependence of microhardness was also measured by an ultra-micro indentation tester. In order to find the method to overcome the limited thickness and the severe radiation damage problem at high dose implantation necessary for the saturation, the nitrogen depth profiles for an energy scanning implantation with a uniform and a non-uniform energy distribution were calculated and compared with those of monoenergetic implantation.

Optical and structural changes of sapphire(0001) substrates implanted with Ti ions or with Ti and 0 ions and subjected to thermal annealing, are examined by optical absorption, RBS-channeling and XRD measurements. The transmittance of the co-implanted sample was larger than that of the Ti-implanted sample. After annealing at 1000 °C, rutile-type TiO 2 microcrystals with (200) orientation were formed in the co-implanted sample of Ti and O ions. Furthermore, a broad optical absorption at 220–340 nm in the co-implanted sample was increased after the annealing. This was possibly due to the formation of TiO2 microcrystals in the sapphire substrate. In contrast to this result, no evidence of the formation of titanium oxide in a crystal structure was obtained for the Ti-implanted sample after the annealing.

We reported that a very smooth surface was obtained by room temperature nitrogen implantation into Zr with the energy increasing mode from 35 to 65 keV even with a high dose of 7×1017 ions cm−2 in contrast to the implantation with the energy decreasing mode and 50 keV mono-energy implantation by which many blisters were observed on the surface. In order to understand the mechanism that causes radiation damage, a dynamic Monte Carlo simulation with the dynamic-SASAMAL code was performed for such an energy scanning mode. The movement of the nitrogen at the stage where the excess nitrogen over stoichiometric concentration just starts to migrate towards the surface was carefully analyzed and the results for the energy increasing mode from 15 to 85 keV with a uniform distribution were compared with that of the energy decreasing mode and 50 keV mono-energy implantation. It was found that, when nitrogen concentration exceeds the stoichiometry, the nitrogen that is enforced to migrate towards the surface is not the newly implanted nitrogen but is the previously implanted one which is moved by the newly implanted nitrogen through binary collisions. The moment given through the collision is towards the surface in the energy increasing mode and it will enhance the migration. In contrast to this, the moment is towards the deeper side in the energy decreasing mode and the mono-energetic implantation, so it will disturb the migration and cause nitrogen gas bubble formation which induces the surface radiation damage with many blisters. Finally, it is proposed that a thick nitride layer without surface damage can be obtained by the energy increasing mode implantation with an adequate energy distribution.

To study the property changes of Zr induced by high dose nitrogen implantation at RT and at 600°C, the depth profiles of nanohardness were measured and compared with those of nitrogen concentration and chemical states of nitride phase. The implantation was performed with 100 keV N + 2 ions and doses from I × 10 16 to I ×10 18 N/cm 2 . The nanohardness was measured by an ultra micro indentation tester. The nitrogen depth profile was measured by NRA using 15 N(α,γ) 12 C reaction and RBS, Depth dependence of chemical state was measured by XPS combined with Ar sputtering. Dose and temperature dependence of the crystalline structure were measured by glancing angle XRD. There was no difference in the XPS spectra between RT and 600°C, and the spectra indicated that ZrN was formed at the depth where nitrogen existed. Since the heat of formation of ZrN is rather high, the depth profile of the implanted nitrogen in Zr was hardly changed up to 600°C. But the XRD patterns showed the increase of crystalline nitride phase with the increase of implantation and annealing temperatures. From the dose and temperature dependence of nanohardness profile, the hardness increase by low dose implantation around 1 × 10 17 ions/cm 2 at both RT and 600 C is attributed to point defects and interstitial hardening and the increase by high dose implantation above a dose around 5 x 10 17 ions/cm 2 at 600 C is attributed to the formation of ZrN phase.

Thin films of TiO 2 prepared by a sol–gel method were irradiated with 100 keV Ar ions. A bilayer (Mo/TiO 2 ) and multilayers (TiO 2 /Mo,Cr,Ag/TiO 2 ) of the thin metal films and TiO 2 were used. After the irradiation, concentration profiles and the structure of the surface layer were studied by Rutherford backscattering spectroscopy (RBS), X-ray photoelectron spectroscopy (XPS) and glancing angle X-ray diffraction (G-XRD). It was found that a ballistic mixing was predominant in the redistribution of Mo and Cr atoms embedded in TiO 2 , and oxides of Mo and Cr were decomposed in metallic states with increasing ion fluence. In the case of TiO 2 /Ag/TiO 2 , Ag colloids were formed in process of a dip-coating of the sol–gel method, and the Ag atoms were dispersed into deeper layer by a grain boundary diffusion. Ion beam mixing in the TiO 2 films produced a slight increase in the optical absorption of visible light.

Optical and structural changes of silica glass substrates implanted with Cu and O ions and subjected to thermal annealing, are examined as a function of the implantation sequence by optical absorption, Rutherford Backscattering Spectrometry (RBS) and thin film X-ray diffraction (XRD) measurements. Before annealing, the distribution of Cu is affected by the implantation sequence and O- followed by Cu-implantation leads to fewer Cu nanoparticles than the Cu- followed by O ion implantation. After annealing, however, the redistribution behavior of Cu and optical absorption features are similar for both co-implanted samples. Nanocrystals of Cu2O are mainly formed by annealing and the absorption peaks at about 340, 450 and 480 nm are observed for the co-implanted samples. The peaks are possibly evidence for the presence of the copper oxide nanocrystals.

Changes in the microstructure and mechanical properties of the surface of glassy carbon implanted with 1.15 MeV Ti ions were examined by Rutherford backscattering spectrometry, Raman spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy and ultra-microindentation measurements. It was found that the surface of glassy carbon was changed to an amorphous structure by Ti ion implantation. The thickness of the amorphous layer, as estimated by the transport of ions in matter (TRIM) simulation, was approximately 1 μm. The glassy carbon surface is composed of many granules which were also increased in size by ion implantation. However, this increase in size was sufficiently small compared with the indenter radius that it had only a minor influence at an early stage of the indentation measurements. The implanted Ti was in the carbide state of TiC. The hardness and elastic modulus were increased by approx. 2.5- and 3.5-fold due to the modification in structure by ion implantation.

In order to find the optimum conditions to obtain films with high photocatalytic property by sol-gel method, depth profiling of oxygen in TiO x film deposited on SiO 2 was carried out using resonant backscattering of 3.045 MeV He ions by the nuclear reaction of 16 O(α, α) 16 O. Depth profiling of hydrogen in the TiO x film was also conducted using elastic recoil detection analysis (ERDA). For the depth profiling by the resonant backscattering analysis, it is necessary to change the incident energy of He ions from about 3.03 to 3.1 MeV in steps of less than 10 keV. In our analyzing system, the ion beam energy of He ++ was scanned by changing a bias voltage supplied to the target holder up to +30 kV without changing the accelerator terminal voltage. The effect of the bias voltage supplied on the sample holder on the energy and the yield of the oxygen peak relative to the titanium and the silicon signal were investigated. The automatic analysis system and the analyzed results are presented.

Using double ion species implantation of metal and oxygen ions, we have examined the possibility of synthesis of metal-oxide fine particles in glass or sapphire surface. Characteristics of ion implanted silica glass and sapphire were examined by RBS, XRD and optical (absorption and photo-luminescence) measurements. 1.8 MeV 1×1017 Cu+/cm2 implantation into silica glass and a successive heat treatment of 1000°, 1h in the air can make Cu fine particles. 1.8 MeV 1×1017 Cu+/cm2 and 1.0 MeV 1×1017 O+/cm2 implantation into silica glass and the successive heat treatment can synthesis Cu2O fine particles of about 8 nm in radius. 1.8 MeV 5×1016 Ti+/cm2 and 1.0 MeV 1×1017 O+/cm2 into sapphire and the successive heat treatment can synthesis Ti02 fine particles of about 10 nm in radius. The TiO2 particles were rutile-type with (200) orientation, which may be related to the (0001) orientation of sapphire substrate. Luminescence from defects in sapphire substrate was observed, but luminescence from the particles could not be detected.

In order to study effects of the ion implantation with a distributed energy and its energy scanning mode on the surface structure and the depth profile, dynamic Monte Carlo simulations were carried out for nitrogen implantations to Zr with uniform energy distribution from 15 to 85 keV, with three energy scanning modes. The modes were: (a) the energy increasing mode from the lowest energy to the highest energy in steps of 1 keV; (b) the energy decreasing mode from the highest to the lowest energy; and (c) the energy sweeping mode of 100 times between the lowest and the highest energies. The calculated results were compared with the experimental results obtained for the implantation with the energy distribution and the energy scanning modes. The depth profiles and the retained fluences of the implanted nitrogen agree well with the experimental results obtained by resonant nuclear reaction analysis. The displacement per atom in the outermost surface layer was in the order of (a), (c), and (b). The d...

In order to form a composite of SiC and Si3N4 on a SiC surface polycrystalline SiC was irradiated with a 50-keV nitrogen ion beam with or without a hydrogen radical beam at elevated temperature up to 1100°C. The depth profiles, the chemical state of elements and the structure of the implanted surface were measured using RBS, NRA, AES, XPS and G-XRD. It was found that graphite-like carbon produced by the nitrogen implantation at 1100°C segregated at the surface and carbon depletion layer are formed beneath the surface. With increasing nitrogen fluence the replacement of carbon by nitrogen took place and β-Si3N4 crystallites were formed on the SiC surface. Preferential loss of carbon atoms in the implanted layer was promoted by irradiation with a hydrogen radical beam during the nitrogen implantation, and the amount of β-Si3N4 crystallites gradually increased.

The thickness of the nitride layer formed by a high fluence nitrogen implantation to a metal surface is limited mainly because of the sputtering effects and the migration of the implanted nitrogen towards the surface. We have investigated nitrogen depth profiles implanted to several kinds of metals theoretically by Monte Carlo simulation using the dynamic-SASAMAL code and experimentally by RBS and NRA using the 15 N(p,????) 12 C reaction. In this paper, the saturation fluence and the saturated nitride thickness were calculated for 1???200 keV nitrogen implantations into several kinds of metals (Al, Ti, Fe, Zr, and Hf). In order to find the method to overcome the limited thickness and the severe radiation damage problem at the high fluence implantations necessary for the saturation, the nitrogen depth profiles for an energy scanning implantation with a uniform and a non-uniform energy distribution was calculated and compared with those of mono-energetic implantations.

A low energy, high dose and temperature ion implantation modeling method is presented. The diffusion equations for impurity and non-equilibrium vacancies are solved taking into account the source functions for impurity atoms and vacancies and the recession of surface due to sputtering. The source functions as well as the sputtering yields and the surface moving velocity are determined from atom collision cascades calculations with the Monte Carlo code CASNEW at dose increments. It is shown for Al + implanted into α-Fe at E 0 = 0.5−2 keV and D = 10 15 −10 18 cm −2 , that radiation-stimulated diffusion (RSD) is significant in temperature range of 100°C t t = 400°C, a penetration depth up to 0.3−0.4 μm is obtained at D = 10 18 cm −2 .

The detailed research of the B4C and SiC sputtering differential characteristics under Ar+ and He+-ions irradiation with the energies 0.5–20 keV has been carried out using both CASNEW and like-TRIM Monte Carlo codes. The major difference between these codes is the following: the dependence of the total interaction cross-section on energy is considered by CASNEW. In its turn it influences upon the collision probability with species and the free flight path. The partial and total yields as well as the angle and energy spectra, ion and point defect depth distributions have been calculated. As it was noticed both CASNEW and TRIM codes give close results at low energies. Differences grow with energy and are more for SiC than for B4C. In both cases the preferred sputtering of the heavier component is observed.

Amorphous Ge films deposited on CaF 2 substrates were irradiated with Ge, Sb and Au ions and their structural changes were examined. Samples during irradiations were kept at a constant temperature about 380°C since a formation of randomly oriented crystals in amorphous matrix was closely related to temperature. It was found that the crystal quality of the epitaxial Ge films became good and the formation of randomly oriented crystals was retarded with increasing ion mass. These results presumably suggested that the crystal quality was correlated with the amount of randomly oriented crystals. Furthermore, it was assumed that the formation of randomly oriented crystals were affected by the single collision cascade whose size was increased with ion mass. From these results, it was concluded that heavy ion irradiation was effective for the enhancement of the epitaxial crystallization and the suppression of the formation of randomly oriented crystals.

Nitrides are formed by high-fluence nitrogen implantation into various metallic targets, and their surface properties are improved. Among them, titanium nitride formation is of great interest in a wide range of technological applications. For nitrogen implantation into Ti with implantation energies of 10 keV to 1 MeV and fluences up to 1 × 1019 ions cm−2, the fluence dependence of sputtering yield, retained fluence and nitrogen depth profiles as well as the implantation energy dependence of saturated thickness of a nitride layer were calculated by computer simulation using the “dynamic SASAMAL” code with various values of threshold displacement energy (Ed) and surface binding energy (Es). The calculated results with Ed = 10 eV and Es = 1.6 eV for nitrogen agreed well with experimental values of the sputtering yield, the depth profile and the retained fluence of nitrogen obtained by Rutherford backscattering spectrometry and resonant nuclear reaction analysis for 50 keV nitrogen implantation at fluences of 6 × 1016 to 2 × 1018 ions cm−2. The thickness of the nitrogen-implanted layer saturated at high fluence and it was nearly equal to the sum of the mean projected range and the straggling value for all energies from 10 keV to 1 MeV.

高線量でZr表面に注入した窒素の挙動を調べるため,50keVの15Nを室温で注入量1×1017から1×1018ions cm-2で注入し,その深さ方向分布を共鳴核反応分析法により測定して,動的なモンテカルロシミュレーションにより得られた理論分布と比較した.核反応は,共鳴エネルギーが429 keVの15N(p,αγ)12Cを用い,ガンマ線を測定した.15Nの注入を14Nの注入と前後して行うことにより,注入した窒素がその注入段階によってどのように分布するかの詳細を明らかにすることができた.又,電算機シミュレーションにおいては窒素濃度に上限を設けない計算と,窒素濃度は50%で飽和し,それ以上の濃度の窒素は照射損傷濃度に依存して表面方向に拡散すると仮定した2種類の計算を行い,測定結果と比較した.その結果,注入した窒素は濃度50%で飽和し,それを超えた窒素は表面に向かって拡散することが分かった.又,注入の後の段階で注入した窒素は,初期の段階で注入したものより広がって分布すること,並びに初期の段階で注入した窒素は引き続く注入により,中央部が押し分けられ二つのピークに分かれることが明らかになった.

Nitride ceramics are formed on metal surfaces by high-fluence nitrogen implantation and the mechanical and chemical properties of the surfaces are modified. However, the thickness of the nitride layer is limited by the sputtering effect and the migration of implanted nitrogen towards the surface. In this work, we studied these effects for nitrogen implantation into several kinds of metals (Al, Si, Ti, V, Fe, Co, Ni, Zr, Nb, Mo, Ta and W) by Monte Carlo simulations using the dynamic sasamal code in comparison with the experimental results obtained by NRA. The dynamic sasamal code takes into account target alterations which occur under high-fluence implantations, so that dynamic changes in composition, deposited energy, retained probability of the implanted ion, sputtering effects, etc. with fluence can be calculated. For nitrogen implantations into metals, the saturated nitrogen concentration is assumed to equal that of the saturated nitride phase and nitrogen atoms above stoichiometry are assumed to diffuse towards the surface. The depth profiles of nitrogen concentration and the retention of nitrogen obtained by the code agree very well with the experimental results for 50 keV nitrogen implantations into metals with fluences of 10 17 –10 18 ions cm −2 . The calculated sputtering yields were compared with the semi-empirical values.

Polycrystalline SiC and a bilayer of thin Zr deposited on SiC (Zr-SiC) were implanted with 50 keV 15 N ions at fiuences in the range (0.25–1.5) × 10 18 ions cm −2 at elevated temperature up to 1100 °C. After implantation, the depth profiles of the elements were measured using Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA) and Auger electron spectroscopy (AES). The structure and chemical bonding state of the implanted layer were investigated by glancing angle X-ray diffraction (G-XRD) and X-ray photoelectron spectroscopy (XPS). It was found that the maximum concentration and halfwidth of the nitrogen profile implanted at 1100 °C were strongly decreased in comparison with those at room temperature, and nitrogen implantation into SiC at 1100 °C resulted in a composite layer of β -Si 3 N 4 and SiC. In Zr-SiC, the interfacial reaction of Zr and SiC was observed at high temperature, and a composite layer of ZrC, β -Si 3 N 4 and SiC was formed by nitrogen implantation.

A simple energy scanning and data acquisition system for nuclear resonance analyses with a narrow resonance is presented. Ion beam energy was scanned by directly supplying a bias in the range −30 to +30 kV to a target holder. Details of the energy scanning and the data acquisition are described. Some examples for the depth profiling of nitrogen implanted into metals using the system with the nuclear reaction 15N(p, αγ)12C at 429 keV are shown in comparison with the calculated results by a Monte Carlo simulation. The data analysis program used to obtain depth profiles from excitation curves is also shown. The target is divided into layers of uniform concentration and the reaction probability in a layer is calculated from a starting depth profile obtained from raw data, using the normalized error function with Gaussian approximation for the overall energy spread. This leads to a very simple computer program, fast to operate with a small computer.

Germanium films were vapour-deposited on thin self-supporting Si substrates of about 1 μm in thickness. During deposition, the substrates were irradiated on the backsurface by a C+ beam with energies between 0.6 and 1.8 MeV in a 〈100〉 channeling condition. The substrate was heated up to about 400°C only by the beam of intensity lower than 2 μA/cm2. Both backward and forward scattering spectrometries combined with the channeling technique were used as a monitor for alignment of the substrate to the 〈100〉 axial channeling condition and characterization of epitaxial Ge films. Heteroepitaxial growth of Ge films was observed for substrate temperature of about 350°C and incident energies of 0.6–1.8 MeV. The results showed that the energy of the assist beam remarkably affects the crystalline quality of Ge film and Si substrate, as well as the morphology of grown Ge.

Amorphous (a-)Ge films deposited on air-cleaved CaF 2 (111) substrates were irradiated with 1.8 MeV Si ions, and the microstructure of the irradiated Ge films was examined by using Rutherford backscattering spectrometry combined with channeling technique, X-ray diffraction measurement and transmission electron microscopy. It was found that the ion irradiation can induce solid phase epitaxial growth (SPEG) of Ge (111) films even at low sample temperature ( T s ) of approximately 200°C, although the films included some randomly oriented crystals. In contrast to this, a-Ge films practically did not crystallize during heat treatment at 200°C and the polycrystal films were only obtained when temperatures reached more than 500°C. These results suggest that ion irradiation enhances the SPEG of a-Ge/CaF 2 heterosystem at relatively low T s values.

Changes in the surface morphology and optical transmittance of polymers, poIy(methyl methacrylate) (PMMA) thin films on quartz glass plates and poly(tetrafluoroethylene) (PTFE) sheets, induced by megaelectronvolt ion implantation, were examined using different ion species, energies, ion current densities and doses. The polymer surface showed remarkable depression after ion implantation. On PMMA, the depression increased with dose and saturated after a dose of about 5×1014 ions cm−2. Higher energy and heavier ions made a larger depression generally. On PTFE, implantation of heavy ion species made a small depression and the dependence on dose was almost linear in the range 1014 to 1015 ions cm−2. PMMA changed its appearance from transparent to white, light brown, brown and finally bla'jk with dose, because of UV-visible light absorption. The width of the absorption band increased with dose, and the implantation of heavier ion species caused wider and larger absorption. Some annihilation of light absorption with time was found at room temperature. Roughening of the ion implanted surface was also observed.

鋭い共鳴幅の核反応を利用した共鳴核反応法は表層における軽元素の深さ分析に特に優れた分析法である.この方法では,分析に用いるプロトンやヘリウムなどのエネルギーを一定の照射量ごとに細かなエネルギーステップで変化させ,発生するガンマ線や粒子線を測定し,励起曲線を得る.本報告ではこの励起曲線を自動的に得るためのエネルギー走査型データ取り込みシステムについて述べた.プロトンエネルギーは加速電圧を一定に保ったまま,試料ホルダーに印加したバイアス電圧を-30kVから+30kVの範囲で一定のビーム電流ごとに~0.5kV刻みで変化させることで走査した.これにより,測定誤差の少ないなめらかな励起曲線を得ることができた.

Retention of nitrogen implanted into various kinds of metals (Al, V, Ti, Fe, Co, Ni, Zr, Nb, Mo, Ta, and W) was calculated by the dynamic-SASAMAL code assuming planer surface binding energy and diffusion toward the surface for nitrogen over the concentration of saturated nitride phase. As the value of surface binding energy ( E s ), the sum of the heat of sublimation of the metal ( H s ) and the heat of formation of the nitride ( H f ) times the nitrogen concentration ( C ) at the surface layer was used ( E s = H s + CH f ). The effects of values of H s , H f , and the displacement threshold energy on the retention were studied. The agreements between the calculated results and the experimental results obtained by NRA using 15 N(p, αγ) 12 C reaction were satisfactory for depth profiles and retention of nitrogen implanted into metals of Al, Ti, Ni, and Zr at a wide range of fluence from 6 × 10 16 to 6 × 10 17 ions cm −2 .

Dynamic SASAMAL code takes into account target alterations which occur under high fluence implantations, so that dynamic changes of the atomic composition, the retention probability of implanted ions, etc., with the fluence can be calculated. The model calculations have been applied for implantations of nitrogen ions of energy 50 keV into zirconium with fluences of 10 17 –10 18 ion cm -2 , assuming (1) no special diffusion and (2) upward diffusion for the extra atoms over stoichiometry. Also, the saturation concentration of nitrogen is assumed to be equal to the saturated nitride phase. Depth profiles of the atomic composition and the retention rate of implanted ions obtained by the calculations were compared with the results of nuclear reaction analysis, and the results obtained with the assumption of “upward diffusion” agreed very well with the experimental results. The depth profiles of the energy deposited by the implanted ions on the target atoms through electronic and nuclear interactions also were calculated. These are discussed in comparison with the results of glancing-angle X-ray diffraction.

Zirconium films were implanted with 15 N ions of energy 50 keV to a total fluence of 1 × 10 18 ions cm -2 in an attempt to study the formation process and thermal stability of ZrN layers produced by high fluence implantation of nitrogen. Subsequent to the implantation at room temperature, samples were annealed at temperatures of 300 °C–900 °C. The depth profiles of the implanted nitrogen were measured by nuclear reaction analysis using the 15 N(p,αγ) 12 C at E R = 429 keV, and the surfaces were examined by thin film X-ray diffraction (XRD) and scanning electron microscopy. There were many blisters 0.2–0.4 μm in diameter on the surface of the as-implanted samples and double peaks were observed in the nitrogen depth profiles; they were in both sides of the mean projected range. It was found that most of the blisters became extinct after annealing above 400 °C, and the XRD peak (111) intensity was increased with the increase in the annealing temperature. Moreover, 14 N and 15 N implantations were superimposed on Zr samples in order to study the atomic migration of nitrogen at each stage of high fluence implantation. It was found that the decrease in the peak at the deeper layers was related to blister extinction and nitrogen diffusion into underling zirconium which could be correlated with radiation damage induced by post-implanted ions.

Au films on optically flat Pyrex glasses or MgO single crystals were implanted with Si, Ni and Au ions with ion energies from 0.75 to 3 MeV and doses from of 5 × 1013 to 5 × 1016 ions cm-2. The changes of their surfaces were investigated from measurements of the surface profiles and light reflection and/or scattering, and from observations by scanning electron microscopy (SEM). After ion implantation the surface showed a depression. The depression increased with increasing dose and mass of implanted ions. The ion-implanted surface became smoother than that of the as-deposited one. The intensity of light scattering was decreased and a metallic brilliance was observed after the implantation. The depression and the morphology changes were caused by sputtering and grain growth. In the SEM observations, the implanted regions were contrasted with as-deposited regions as blacker in secondary electron images and as whiter in composition images of reflected electrons. The impurity level of the films appeared to diminish after the ion implantation.

Au films are deposited on air-cleaved MgO(100) substrate by forward sputtering under various conditions of ion energy and ion species and the differences in their structural features are examined. The films have a mixture of (111) and (100) orientations. When the ion energy decreases or when the ion mass increases, the growth of (100)-oriented deposits is enhanced. Mostly (100)-oriented Au films are obtained below 500 °C. The defect density in Au films deposited by Au 3+ ions seems to be lower than that in Au films deposited by other ions. The surface morphology is also changed by the ion species. With lighter ions (C + , O + ) a relatively uniform surface is observed, while with heavier ions (Si + , Au 3+ ) a grain structure becomes clear. From these results it is believed that the structural features of Au deposits can be favourably changed by forward-sputtering deposition.

Depth profiles of nitrogen implanted into Zr with an energy of 50 keV were calculated by dynamic SASAMAL code with three different assumptions for the diffusion of excess atoms over stoichiometry, i.e., ‘no diffusion', ‘both-sides-diffusion’ and ‘upward-diffusion'. To distinguish nitrogens implanted certain stage of implantations, alternate implantations of 15N and 14N were used. The results were compared with the experimental results by the resonance nuclear reaction analysis, NRA. For 15N implantation with fluences from 1 × 1017 to 1 × 1018 ions/cm2, the calculated results with ‘upward-diffusion’ agreed very well with the NRA results for all fluences. For the depth profile of pre-implanted 15N (1 × 1017 ions/cm2), which was changed by the subsequent 14N implantation with fluences of 1 ∼ 10 × 1017 ions/cm2, the agreement with the NRA results was satisfactory until the 14N fluence did not exceed 5 × 1017 ions/cm2, but for higher fluences, the retained probabilities of 15N obtained by the ‘upward-...

In order to evaluate the depth profiles of ions implanted at high fluence, the behavior of nitrogen implanted into Zr samples was studied in detail by nuclear reaction analysis using the 15 N(p, αγ) 12 C reaction at E p = 429 keV. Zr samples were implanted with 15 N ions of 50 keV to a total fluence of 10×10 17 ions/cm 2 at room temperature and 500°C. It was found that the nitrogen concentration exceeded 50% on both sides of the mean projected range ( R p ) for a fluence of 7×10 17 ions/cm 2 . The layers of over-stoichiometry were removed by subsequent ion implantation and then a trapezoidal profile was obtained for a fluence of 10×10 71 ions/cm 2 . Moreover, 14 N and 15 N implantations were superimposed on Zr samples in order to measure the atomic migration of pre-implanted 15 N caused by the subsequent 14 N implantation. It was found that nitrogen atoms near R p moved to both sides of R p by the collision cascade and the peak of the depth profile of 15 N split into two peaks with increasing 14 N ion fluence. These experimental results on the depth profile were compared with the theoretical results obtained by Monte Carlo simulation of the dynamic SASAMAL code, in which excess atoms over stoichiometry are assumed to diffuse depending on the degree of the radiation damage. Good agreement with theoretical results was obtained.

100 nm thick chromium layers were deposited on hot-pressed silicon nitride ceramics and irradiated at room temperature with 430 keV Si + ions to fluences ranging from 2.5 × 10 15 to 4 × 10 16 ions cm −2 . RBS, TEM and XPS techniques were used for the characterization of the irradiated structures. There is no ion induced interfacial layer, but a very limited reaction takes place between the metal film and the substrate with at least one reaction product, CrN. Some preliminary results on adhesion enhancement are also presented and the role of pre-deposition sputter cleaning of the substrate is discussed.

High-fluence implantations of 100 keV N2+ ion into a zirconium layer deposited by an electron beam were carried out at room temperature and at liquid-nitrogen temperature with and without nitrogen gas of a pressure of 1 × 10−4 Torr. Depth profiles of atom concentrations were determined by Rutherford backscattering spectrometry, Auger electron spectroscopy, and resonance nuclear reaction analysis. The experimental results were compared with the theoretical results obtained by Monte Carlo simulations of the dynamic-SASAMAL code. The depth profiles measured by RBS agreed well with the calculated profiles for all fluences from 1 × 1017 to 5 × 1017 ions/cm2, but differed from those obtained by AES indicating the existence of easily released nitrogen in the Zr specimen implanted with nitrogen at high fluence. Glancing angle X-ray diffraction was used to confirm zirconium nitride formation.