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GaN-on-Diamond high electron mobility transistors were successfully fabricated by surface-activated room-temperature bonding technique. Various diamond substrates were finely polished and bonded to GaN-HEMTs by surface-activated room-temperature bonding. Fabricated devices showed superior characteristics in thermal dissipation compared to the device with conventional structure.

Diamond semiconductor has attracted attention for use in next-generation high-power, low-loss, high-radiation proof power devices. Heavily B-doping of diamond produces low-resistivity contacts that enhance the maximum output current, however, unintended lattice strain cause defect formations, degrading the device performance. In this study, we investigated the doping-induced lattice strain of heavily B-doped (100) films fabricated by hot-filament chemical vapor deposition. X-ray reciprocal space mapping indicated coherent, pseudomorphic growth between film and substrate. The perpendicular lattice strain as a function of B concentration followed Vegard's law, which accounts for substitutional incorporation. Synchrotron X-ray absorption fine structure showed no signature of lower-coordinated B-clusters. We believe that maintaining pseudomorphic growth is a key factor in suppressing electrically non-active B impurities.

Single-crystal diamond was grown over inch size area by using microwave plasma chemical vapor deposition with introduction of Argon. Increase of the growth rate was confirmed by Ar addition under various gas pressures. Improvement of the uniformity of the substrate temperature as well as the growth rate was observed by introducing Ar; over 40% non-uniformity was reduced to

Aiming at improving performance of inertial confinement fusion (ICF) targets, we developed synthesis technology of diamond capsules. In direct-drive ICF for which a spherical target capsule is irradiated directly with intense laser light, laser imprinting due to irradiation non-uniformity on the capsule surface degrades symmetry of the target implosion and performance as a result. We demonstrated that material stiffness is the effective parameter for mitigation of laser imprinting [Kato, et al., Phys. Plasmas, 25, 032706 (2018)]. In this study, we fabricated polycrystalline diamond capsules as the ablator material of direct-drive ICF targets by using the hot filament chemical vapor deposition method. The capsule (diameter ~500 μm) with sphericity 99.7%, film thickness

Heavily B-doped p+ diamond (100) thick films were grown by hot-filament chemical vapor deposition (HFCVD). Low resistivity ( 100 μm). Freestanding crack-free films were prepared by removing the seed substrates via laser-cut and mechanical polishing processes. The X-ray diffraction rocking curve (004) spectrum showed the full-width at half maximum value of 25 arcsec, equivalent to that of the seed substrates employed. Vertical Schottky barrier diodes showed clear rectifying actions with low leakage current level.

Single-crystal diamond (SCD) is considered to be an ideal material for next-generation power devices. Plasma-assisted polishing (PAP) without using an abrasive was applied to polish SCD fabricated by chemical vapor deposition. Argon-based plasma containing water vapour was used in the PAP to modify the surface of polishing plate and SCD (100), and SCD was polished under a polishing pressure ranging from 10 to 52.6 kPa. Raman spectroscopy measurement showed that there was no residual stress on the polished SCD surface, and a polishing rate of 2.1 μm/h and a surface roughness of 0.13 nm Sq were obtained.

This report is the first describing experimental evaluation of Fano factor for diamond detectors. High-quality self-standing chemical vapor deposited diamond samples were produced using lift-off method. Alpha-particle induced charge measurements were taken for three samples. A 13.1 ±0.07 eV of the average electron–hole pair creation energy and excellent energy resolution of approximately 0.3% were found for 5.486 MeV alpha particles from an 241Am radioactive source. The best Fano factor for 5.486 MeV alpha particles, calculated from experimentally obtained epsilon values and the detector intrinsic energy resolution, was 0.382 ± 0.007.

In order to achieve the ignition by direct-drive inertial confinement fusion (ICF), smooth and symmetric fuel capsule is required. Our previous research found that stiffness of the capsule material contributes to reduce the laser imprinting. Therefore, diamond is considered to be the most promising candidate as the stiff ablator material for direct-drive ICF capsule. In this study, aiming at improving the surface roughness on the diamond capsule, we obtained dependence of methane concentration and gas pressure on surface roughness and morphology by hot filament chemical vapor deposition technique.

To fast remove the surface damage layer from single-crystal-diamond, we have developed a chemical etching process using molten KCl and KOH solution at high temperature around 1100 °C. High removal rate about R {001} = 2.0 μm/h, R {101} = 20 μm/h and R {111} = 26 μm/h was achieved for the {001} sample surfaces, {101} and {111} sample edges, respectively. Laser microscope observation has confirmed that the {001} surface flatness has been greatly improved after etching and surface roughness formed during previous lift-off process has been effectively removed.

The piezoresistivity is a change in the electrical resistivity of a semiconductor when mechanical stress is applied. A number of studies of the polycrystalline diamond (PCD) piezoresistivity have been reported before. And it was examined that the shear piezoresistive coefficients in single crystalline Silicon (Si) and Germanium (Ge) are exceptionally large due to its crystal orientation anisotropy. However, the single crystalline diamond (SCD) piezoresistivity has been rarely investigated with respect to crystal orientation anisotropy. In this study, the piezoresistive coefficients π11, π12 and π44 of SCD were measured experimentally with the SCD piezoresistors fabricated from the boron (B)-doped SCD thin films. It was found that the coefficient π44 of SCD at 4.5 ppm B/C ratio were 18.3 and 12.0 times as large as the coefficient π11 of that and the coefficient π44 of PCD, respectively.

By hot-filament (HF) chemical vapor deposition (CVD), heavily boron (B)-doped single-crystal diamond (100) films were fabricated and their structural and electrical properties were studied. We did not observe the soot formation, which is frequently observed and limits the performances in the case of microwave plasma (MWP) CVD. The B concentration was successfully controlled over the range from 1019 to 1021 cm− 3. Hillock-free films were obtained, whose mean surface roughness measured by atomic force microscopy (AFM) was less than 0.1 nm. From the reciprocal space mapping (RSM) around 113 diamond reflection, it was revealed that the films possess the smaller lattice expansion than that expected from the Vegard's law. The room-temperature resistivity was decreased lower than 1 mΩ·cm for B concentration ~ 1021 cm− 3. These results indicate that the HFCVD possesses large potential for fabricating the device-grade p+ diamond.

A method to increase the thickness of diamond layers grown by plasma chemical vapor deposition (CVD) is presented. Undesired polycrystalline diamond growth that typically occurs during long time periods of deposition was suppressed by introducing oxygen into the source gas mixture. To maintain a stable growth environment, a movable stage was introduced to control the distance from the top surface of the substrate to the core of the discharge region. This made it possible to sustain uninterrupted growth for over 200 h until the thickness of the CVD layer has reached 6 mm. The use of this continuous deposition process prevents the formation of growth interfaces, which are believed to be an origin of dislocations, in the CVD-grown layer.

Hot filament chemical vapor deposition (HFCVD) possesses a large potential to scale-up for the growth of single-crystal diamond (SCD). This study investigates the crystalline qualities of SCD fabricated by HFCVD. A tungsten impurity level of 10 18 cm − 3 was detected with secondary ion mass spectroscopy. The full-width at half maximum (FWHM) of the rocking curve (004) was 39.5 arcsec, where that of seed substrates was 42.8 arcsec. A clear free-exciton recombination radiation was observed in cathodoluminescence spectra. The Raman spectra presented a single peak centered at 1333.2 cm − 1 with a FWHM value of 1.9 cm − 1 . These results indicate that the HFCVD-grown SCD has good crystalline quality comparable to the seed substrates.

The effect of neutron irradiation on recovery (annealing) of irradiation damage has been investigated for self-ion implanted Si. A damage layer was introduced by 200 keV Si+ implantation to a fluence of 5 × 1014 Si/cm2 at room temperature. The damaged samples were neutron-irradiated to 3.8 × 1019 n/cm2 (fast neutron), without intentional heating, in the core of the Kyoto University Reactor. During neutron irradiation, the samples were heated only by nuclear reactions, and the irradiation temperature was estimated to be less than 90 °C. The damage levels of the samples were characterized by Rutherford backscattering with channeling. Reduction of damage peaks as a result of neutron irradiation was clearly observed in the samples. The annealing efficiency was calculated to be 0.44 defects/displacement.

We have developed a gamma-ray detector based on a single-crystal diamond in order to improve the heat and radiation resistances of gamma-ray monitors. We fabricated prototypes with two types of diamond grown by a chemical vapor deposition method. The count rates with temperature and accumulated dose were obtained using a 137Cs gamma-ray source, then the errors at full scale (%FS) were evaluated using a method to reduce the dark count. The prototype-A worked to 643 K within 2.9%FS and to 3.1 MGy within 4.9%FS; on the other hand, the prototype-B worked to 545 K within 3.4%FS and to 5.0 MGy within 0.47%FS. This study demonstrates that the diamond semiconductor was promising for monitoring with enhanced heat and radiation resistances.

We conducted a repetitive process for tiling freestanding substrates made from one identical seed crystal. After the mechanical polishing of both sides of the tiled substrates over the inch-sized area, the boundaries between the constituent substrates were barely recognized. By repeating the tiling process, we succeeded in fabricating several freestanding wafers with a size of 1.5 in. (area of approximately 20 × 40 mm2). For this wafer size range, we found that non-uniformities in the morphology, as well as the growth rate, became remarkable. By qualitative comparison between the numerical predictions and the experimental observations, we discussed the dominant factors that control the non-uniformity.

The microscopic surface morphology of “lifted-off” surfaces, produced via ion implantation was observed by atomic force microscopy. A polished single-crystal diamond substrate with an average surface roughness of less than 0.1 nm was used for precise observations. After the lift-off process, the lifted-off surface became rough with pits appearing. Hydrogen plasma treatment close to the chemical vapor deposition conditions for diamond (1150 °C, 160 Torr) completely removed these pits and the surface was subsequently covered by a strip-like structure consisting of atomic steps. The surface roughness, however, was not further influenced by the plasma treatment. The observed morphological evolution reflects the graphite/diamond interface formed by the lift-off.

Thick (∼100 μm) undoped diamond films were grown homoepitaxially on single crystal (SC) diamond substrates by microwave plasma chemical vapor deposition (CVD). To form a freestanding SC diamond film (plate), the substrate was pre-ion-implanted with high-energy ion beams before the film growth, and after the thick-film deposition, the substrate was eliminated using a lift-off method, resulting in fabrication of a SC CVD diamond plate. Two samples were prepared; sample 1 was grown on a (0 0 1) oriented, nitrogen doped CVD SC diamond at ∼900 °C with the input microwave power of 1.7 kW, while sample 2 was grown on a (0 0 1) oriented, high-pressure high-temperature synthesized type-Ib SC diamond at ∼900 °C with the input microwave power of 1.25 kW. The formed SC plates have high optical transparencies, indicating no remarkable optical absorptions seen in the wavelength from ultraviolet to near infrared. The photoluminescence (PL) spectra of both samples show strong free exciton FE peaks, while in sample 2 relatively strong optical emissions corresponding to nitrogen related centers were observed in the visible region. After the metal electrodes were formed on both faces of the SC diamond plate to fabricate a sandwich-type diamond particle detector, the energy spectra of 5.486 MeV α-particles from 241 Am were measured. The charge collection efficiencies (CCEs) of sample 1 were CCE = 98% for a hole transport and CCE = 89% for an electron transport, respectively, while CCEs of sample 2 were CCE = 80% for a hole transport and CCE = 78% for an electron transport, respectively. These results indicate that both holes and electrons in sample 2 were trapped much more than those in sample 1. Possible candidates of carrier capture centers are nitrogen and/or nitrogen-vacancy centers observed in PL, nonradiative defect (complex) centers, extended defects such as threading dislocations observed in micrographs taken with polarizers. The different growth conditions most likely affected crystallinity and responses to α-particles of the samples.

As part of the development of diamond radiation detectors for energy spectrometry, quality improvement of CVD diamond single crystals was conducted mainly by measures of single diamond substrates. To suppress stress resulting from unconformity of lattice spacing between a substrate and a grown layer, which sometimes causes breakage, HP/HT type IIa diamond single-crystal substrates were adopted, and it resulted successfully. In addition an off-axis (001) surface was fabricated on the substrate to reduce abnormal growth. A lift-off method was adopted to reuse the HP/HT type IIa substrate with an off-axis (001) surface. Judging from peaks caused by free exciton recombination in cathode luminescence spectra, growth conditions more strongly affected the diamond crystal quality than substrates of any kind. Energy resolution of 0.6% for alpha particles was obtained by one CVD diamond single crystal. Charge collection efficiency of approximately 100% and 95% for holes and electrons was achieved. Step bunching caused by residual gas was observed on the grown CVD diamond surface. From the perspective of charge carriers' transportation measurement, the reduction of residual gas and optimization of growth conditions are indispensable.

Lattice structures of freestanding, large (~ 9 × 9 mm) nitrogen doped single crystal (SC) diamond plates were investigated mainly by X-ray diffraction including a reciprocal space mapping (RSM) method. After a plasma-chemical-vapor-deposited thick homoepitaxial diamond film was grown at a high-speed on type-Ib (001) diamond, a SC freestanding diamond plate was fabricated by separation of the substrate from the film by a lift-off process using high-energy ion implantation. Due to the use of the lift-off process, there is a thin (~ 1.6 μm in thickness) residual diamond substrate on the back-face of the freestanding plate. It was found that only in the case of the X-ray incidence on the back-face, the RSM around (113) diffraction pattern displayed a long streaky pattern along the [001] direction. This indicates a gradual lattice expansion only along the growth direction. The maximum value of the lattice expansion was approximately + 0.7%. Such a lattice expansion probably occurs around the interface between the thin residual substrate and the film.

Crystallinity of a freestanding large (size: ~ 9 × 7 mm) undoped single crystal (SC) diamond film grown by plasma chemical vapor deposition (CVD) and radiation response of a sandwich-type radiation detector made from this SC plate to α particles were investigated. The freestanding SC film was formed by elimination of a substrate using a so-called “lift-off method” after the growth of a thick-film on a pre-ion-implanted substrate. The formed SC plate has a high optical transparency, indicating no remarkable optical absorption seen in the wavelength from ultraviolet to near-infrared region. In the energy spectra of 5.486 MeV α-particles, relatively sharp peaks were observed for both hole and electron transits. For the hole transit, the peak resolution of the pulse height distribution and charge collection efficiency (CCE) were ~ 0.7% and 98%, respectively. On the other hand, for the electron transit, the peak resolution and CCE obtained were ~ 4.4% and 89%, respectively. In the photoluminescence spectrum at room temperature, a strong sharp peak around 235 nm corresponding to free exciton and a weak visible band mainly related to nitrogen-vacancy complex were observed. The spectral width of the (004) plane X-ray rocking curve was 16.5″. The micrograph taken using crossed-polarizers demonstrated that there are some white regions and four-petaled patterns, originating from internal strain and most likely threading dislocations, respectively.

We have developed a technique to fabricate “tiled clones”, a new type of mosaic wafers. This technique uses “cloned” substrates, which come from an identical seed substrate. Four to eight 10 mm × 10 mm “clone” substrates, each at most 1 mm thick, were connected to form one large wafer with a range of area of 20 mm × 20 mm-20 mm × 40 mm,. These clone substrates could be connected relatively smoothly, with abnormal growth being suppressed, and the boundaries among the constituent clones were almost invisible. In addition to observation of their cross sections, Raman spectra and X-ray diffraction was measured for each of these tiled clones. FWHM of the X-ray rocking curve was around 10–50 arcsec in the areas away from the boundaries.

Seen as the future of wide band gap semiconductor materials, single-crystal diamonds need to be fabricated in at least inch-size wafers if they are to be of use in industry. The key methods required to achieve this are 1) improving the growth of single crystals with sufficient quality over large areas at an acceptable growth rate, 2) enlarging the seed crystal, and 3) improving the fabrication of the freestanding wafers. This paper briefly reviews recent progresses and reports the most recent results of our research of solving these technical problems.

Diamond mosaic wafers in which several seed crystals are connected laterally by chemical vapor deposition (CVD) are promising large-scale substrates for diamond electronics. One of the prime concerns of the applicability of diamond mosaic wafers is the presence of highly defective coalescence boundaries, which degrade the electrical performance. For Schottky barrier diodes (SBDs), a large leakage current with an inferior Schottky barrier height has been observed at mosaic boundaries. To further improve the device uniformity, high-quality, low-dislocation film growth is required. Here, we introduced a buffer layer to mitigate the influence of coalescence boundaries on diamond mosaic wafers. Diamond film growth by hot-filament CVD accompanied by tungsten incorporation effectively suppressed dislocation propagation from the mosaic substrate to the epilayer. After insertion of the buffer layer, SBDs showed improved rectifying behavior with suppressed leakage current at coalescence boundaries. In addition, the forward/reverse characteristics were essentially identical and high electric breakdown strength exceeding 3 MV cm−1 was demonstrated regardless of the presence of coalescence boundaries when the buffer layer was included.

In this article, we present a study of surface stress measurements of a thick single-crystal diamond (SCD) layer (110 μm) deposited onto a high-temperature high-pressure (HTHP) Ib substrate. The measurement is based on observations of the deformation of the backside of the HTHP substrate due to internal stress that varies as the thickness of the SCD layer is modified by ion-beam etching. The deformation is obtained from the height-distribution analysis of interference microscopy (IM) observation. The results show that the tensile surface stress σ increases linearly with SCD-layer thickness with t f according to σ = 0.065t f MPa/μm. The tensile surface stress may be attributed to the intrinsic stress that originates from the lattice mismatch between the CVD-diamond layer and the HTHP-Ib substrate. The increased internal stress is a principle cause of crack formation of the crystal.

Dislocations in semiconductor crystals are desirably minimized as much as possible, since their presence typically deteriorates device performance. While diamond electronics have demonstrated superior device properties, they have not fulfilled their material limit yet. To further improve device performance, a low dislocation density and a high-quality epitaxial layer are required. In this study, diamond films are homoepitaxially grown by hot-filament chemical vapor deposition accompanying W incorporations from heated metal-wires. The films exhibited better crystalline quality than seed substrates: a large reduction of threading dislocation from 2 × 106 to 3 × 104 cm−2 was demonstrated. The dislocation propagation was partially annihilated by W impurities. The electrical properties of Schottky barrier diodes after dislocation reduction were highly uniform, improved rectifying actions.Dislocations in semiconductor crystals are desirably minimized as much as possible, since their presence typically deteriorates device performance. While diamond electronics have demonstrated superior device properties, they have not fulfilled their material limit yet. To further improve device performance, a low dislocation density and a high-quality epitaxial layer are required. In this study, diamond films are homoepitaxially grown by hot-filament chemical vapor deposition accompanying W incorporations from heated metal-wires. The films exhibited better crystalline quality than seed substrates: a large reduction of threading dislocation from 2 × 106 to 3 × 104 cm−2 was demonstrated. The dislocation propagation was partially annihilated by W impurities. The electrical properties of Schottky barrier diodes after dislocation reduction were highly uniform, improved rectifying actions.

Diamond is a hopeful candidate for power switching device which can operate at high temperature as a “Cooling system free” device, yet at a high current. Recently we have developed a 3D diamond CVD growth method coupled with a sophisticated “direct wafer fabrication technique” to fabricate diamond wafer without slicing. Currently, half inch size single crystal diamond substrates are available for R&D of diamond device. Using this technique, we have increased the device fabrication size from 3x3mm2 to half inch wafer. In this paper, we present the results of measurements on the first device fabricated on a half inch size CVD substrate. We have carried out the first device characteristics mapping for diamond, and have observed the influence of substrate characteristics on the SBD characteristics.

Using lift-off method, we synthesized large self-standing plasma CVD diamond films on various substrates. Charge carrier transportation in diamond was measured using α particle measurements and TOF methods with a short-pulsed UV laser. The high-quality films were synthesized rapidly. We observed the maximum transit time of holes and electrons shorter than 5 ns. The lift-off method is useful to fabricate the high-quality diamond with excellent drift velocities of the charge carrier. The charge transport characteristics of our diamond films are comparable to those of a commercially available (Element Six Ltd.) electronics grade IIa diamond single crystal.

Recent developments in producing large single crystal CVD diamond plates are reviewed. The developments consist of synthesis of large single crystal diamond and production of single crystal diamond plates from the bulk diamond by the lift-off process. Combining these developments, half-inch single crystal CVD diamond plates have been successfully produced.

We have investigated the crystallinity of a self-standing homoepitaxial diamond film grown at a high rate using a polarized optical microscope, X-ray rocking curves and X-ray topographs. The self-standing film was made by removing a synthetic type-Ib(001) substrate after the film growth using a “lift-off process”. The cross-nicol optical microscope image demonstrated that there exists strain spreading at a relatively large area in the film and the strain inherits over that in the substrate. From cross-sectional X-ray topographs, the dominant defects, observed as dotted patterns in plan-view topographs and micrographs, are dislocations extending along the film growth direction 〈001〉 and generating at the interface between the film and the substrate. The density of such defects counted from these measurements was ~ 1 × 10 3 cm − 2 . The dotted patterns observed in X-ray topographs of (220), (− 220) and (400) diffraction planes are almost the same with each other, suggesting that dominant line defects along 〈001〉 are mixed dislocations with a burgers vector directing between 〈001〉 and in-plane of the sample. The high resolution X-ray rocking curve showed that the peak is very sharp with full width at half maximum of 7.56″, which indicates that imperfection of our single-crystal diamond plate is almost the same as that of high-quality high-pressure high-temperature, synthetic type-Ib diamond.

Multiple P or S hot ion implantation to diamond substrates was performed at 800°C. Optical absorption spectra indicated that instantaneous annealing during hot ion implantation occurs. Temperature dependence of resistance demonstrated that a P as-implanted sample using a homoepitaxial diamond film substrate emerges a weak doping effect. Also on S implantation, a presence of a weak doping effect was observed in an as-implanted sample, but it was suggested that the dopant is not S itself but S and defect complex. However, post-implantation annealing resulted in high resistance of the samples and missing of such weak doping effects.

We have studied MWPCVD for synthesis of diamond crystals to achieve high growth-rates over an area with 1-inch in diameter under input-power less than 5 kW. The numerical and experimental studies have conducted for both of conventional and proposed configurations. Qualitative correspondences between the numerical predications and experimental observations were found. For both configurations, we have been able to achieve the growth-rates larger than 50 μm/h over the large area under the limited input-power.

A process of making a large, thick single crystal CVD diamond plates has been developed. This process consists of high rate homoepitaxial growth of CVD diamond and subsequent lift-off process using ion implantation. By using this process, single crystal CVD diamond plates with the size of about 10 × 10 × 0.2–0.45 mm3 have been successfully fabricated. The crystallinity of the CVD diamond plates has been evaluated by X-ray topography, polarized light microscopy and high resolution X-ray diffraction. The results indicate the pretreatment of the seed substrate has strong effect on the crystallinity of the CVD diamond plates.

To specify the most important factor which dominates macroscopic surface shape of single crystal diamond synthesized by microwave plasma chemical vapor deposition, we have carried out numerical simulations and corresponding experiments. Comparison between the numerical and experimental results has shown that temperature distribution on the top surface of the substrate predominantly controls the surface shape.

We have simulated distributions of temperature and gas flow inside a reactor for chemical vapor depositions of diamond. In the simulation, a diamond substrate with finite thickness is taken into account. The distributions in region close to the substrate are studied for various types of substrate holders. Qualitative correspondences between the calculated results and experimentally observed macroscopic surface morphologies of diamond are found. These correspondences imply importance of controlling the local distributions for syntheses of thick single crystal diamond.

Repetition of high rate homoepitaxial growth of diamond by microwave plasma CVD has been successfully applied to the growth of single-crystal diamonds with the thickness as large as 10 mm. By optimizing the shape of the substrate holder, smooth and flat surface morphology suitable for regrowth has been obtained. Using this condition, a 4.65 ct single-crystal diamond with the thickness of 1 cm has been grown on a HPHT synthetic 5 × 5 × 0.7 mm3 seed by 24 times repetition of high rate growth with the average growth rate of 68 μm/h. Also a method to enlarge the size of diamond three-dimensionally by growing on side {100} surface of a thick diamond prepared by this technique has been demonstrated.

Nitrogen diffusion in stainless steel at elevated temperatures during low-energy N ion implantation is studied. Stainless steels in the temperature range from room temperature (RT) to 600 °C are irradiated by isotopically mass selected ∼1 keV 15 N + ion beams (less than several 10 μA/cm 2 ) in an ultrahigh vacuum chamber. The depth profile of implanted N atoms as a function of substrate temperature is investigated by nuclear reaction analysis (NRA) in order to evaluate the diffusion coefficient and activation energy of N atoms in the stainless steel. The results demonstrate that the N diffusion during irradiation with low current density (less than several 10 μA/cm 2 ) N ions is faster than that during a postanneal process after N ion irradiation at RT and is slower than that during higher current density (∼mA/cm 2 ) N implantation previously reported. The activation energy of the N diffusion in this study is ∼1 eV, which is comparable to that of the ion irradiation experiment using higher current density beams, e.g., ∼mA/cm 2 , and is lower than that of the postanneal process. The N diffusion mechanism associated with ion irradiation in stainless steel is discussed.

A plasma source using arc-like discharge for plasma-based ion implantation (PBII) has been developed. Molten metals such as titanium are used as cathode in this plasma source. The utilization of the arc-like discharge in PBII systems is reported for the first time. The plasma source with the arc-like discharge provides a new promising method to enable macroparticle-free process without magnetic filter. The characteristics of the arc-like discharge using the hot cathode and application for a plasma source of PBII process are reported. The implanted dose distribution on a substrate with spherical shape is measured using Rutherford back scattering (RBS).

Nanoscale metallic multilayers have been deposited by a pulsed double-cathodic arc deposition with varying thicknesses of each layer from a few to tens of angstroms and examined by cross-sectional transmission electron microscopy (XTEM). TRIDYN computer simulations are performed to get a better understanding of the nanoscale deposition of multilayers during the cathodic arc deposition process. Their results are compared with the experimental data. For the higher ion fluence (>1.0×10 16 ions/cm 2 ) and larger bilayer thickness (>2 nm), the periodicity of multilayers was good. However, the results of the simulations for the lower ion flux and smaller bilayer thickness reveal that the individual layers are intermixed and diffused. The experimental results are in good agreement with those of simulations that the limit of bilayer period of the ultra-thin multilayers is approximately 2 nm in the present case.

Damage of polyimide windows for external ion microbeams was monitored by analyzing backscattering protons from the window. A 1.5 MeV proton microbeam focused to approximately 50 × 50 μm2 was transmitted through the polyimide window from vacuum to oxygen atmosphere. The changes in backscattering spectra of the window were monitored as a function of irradiation dose up to 2 × 1018 H+/cm2. For comparison, the polyimide window was irradiated in vacuum in the same way as the oxygen case. The backscattering spectra drastically changed in the case of oxygen. We observed that the carbon spectrum width, corresponding to the thickness of the window, substantially decreased with increasing the irradiation dose. The in situ monitoring of backscattering protons demonstrated the ability to detect the damage of the window and to predict the rupture of the window.

Halogen ions (Cl, Br and I) and copper ions have been implanted in silica glass at the same dose and at energies of the order of MeV, sequentially. The coordination structure of implanted copper atoms has been studied by X-ray absorption fine structure spectroscopy. It was found that implanted Cu atoms were coordinated with two oxygen atoms in all the as-implanted glasses. Heat treatment in air caused the formation of copper–halogen bonds without the formation of halide crystals. Further heat-treatment caused the formation of halide crystals in the glasses.

In this contribution we apply a recently developed technique to measure the porosity of thin films by means of an electrochemical method. As a model system thin iron films deposited on silicon wafers and coated with amorphous carbon protective films were chosen. The depositions were done with coaxial arc deposition. Rutherford backscattering spectroscopy, scanning electron microscopy and electrochemical measurements were carried out to characterize the films in dependence on deposition parameters and pre-cleaning procedures. Experiments show the validity of the introduced model. With the presented measurement technique it will be possible to study the dependence and control ability of thin films porosity by energetic ion bombardment during film growth. This is a relevant application for the corrosion properties of bulk materials coated with thin protective films which strongly depend on their porosity.

Influence of deposition parameters on the deposition rate and the mechanical properties of diamond like carbon (DLC) films deposited by plasma based ion implantation and deposition (PBII) using combined radio frequency (RF) and negative high voltage pulses has been investigated. The hardness and deposition rate for the typical deposition condition is higher for the acetylene (C2H2) plasma than for the methane (CH4) plasma. Unlike a pulsed glow discharge process, the deposition rate can be controlled by both the average input RF power and the process pressure. The DLC films show relatively low compressive stress (0.35 GPa) at the high process pressure (2 Pa), but the stress increases at the low process pressure region (

The present work reports on the structural and transport properties of nanostructured Fe in thin Cr films, produced by implantation of Fe + ions. The implantation process introduces defects in these films forcing accommodation to take place during and after the process that induce the segregation of immiscible species. This gives rise to the nanostructured Fe granules in much faster time scales than when conventional processes are used. A comparison is made with systems produced by depositing Fe between Cr layers by means of the arc-vacuum deposition method at equivalent concentrations. Resistivity versus temperature curve shows a clear minimum at fairly high temperatures for the implanted samples only. This effect is probably due to electronic interactions with the Fe nanostructures formed by segregation and to coupling with defects.