Keiichi Terashima

Change in atomic density of glassy carbon by Na ion implantation

Abstract A study has been made of the change in atomic density of Na-implanted glassy carbon (GC) with a density of 1.5 g/cm 3 , comparing the depth profiles measured by secondary ion mass spectrometry (SIMS) and Rutherford backscattering spectrometry (RBS). Na ions of 50 keV were implanted in GC with doses ranging from 5×10 14 to 1×10 17 ions/cm 2 at room temperature. SIMS was carried out, using Cs + ions of 8.5 keV as primary ions. Secondary ions detected were 12 C + and 23 Na + ions. RBS was carried out using 1.5 MeV He ions with a fluence of 10 μC. SIMS results show that the Na depth profile is Gaussian for a low dose and a Gaussian-like distribution with a hump for intermediate doses. The profile for the highest dose shows Na enrichment at the surface and wide spreading. The RBS results were similar to those of SIMS. The correspondence between SIMS and RBS profiles suggests that the atomic density of implanted layers increases from 1.5 to 2.2 g/cm 3 at intermediate doses and returns to 1.7 g/cm 3 at a high dose. It was concluded that Na implantation in GC causes the increase in atomic density of GC surface layers.

Surface modification of electrodeposited chromium films by ion implantation

Abstract Electrodeposited chromium films implanted with nitrogen and argon ions were characterized by surface analysis, surface hardness, wear, and corrosion. Depth profiles were examined by Auger electron spectroscopy and the chemical bonding state was estimated by X-ray photoelectron spectroscopy. The near-surface hardness of nitrogen-implanted chromium was measured with a Vickers microhardness tester and a dynamic ultramicrohardness tester. Wear tests were carried out using an Ohgoshi rapid wear-testing machine and a Taber abrasion test apparatus. The corrosion resistance was investigated by the electrochemical method of cyclic voltammetry in 0.05 M H 2 SO 4 . The following results were obtained. 1. (1) Nitrogen implantation caused the surface hardness to increase. 2. (2)NNitrogen-implanted chromium showed a remarkable wear resistance. 3. (3) The corrosion resistance of chromium was improved markedly by nitrogen implantation. 4. (4) Nitrogen depth profiles showed definitely that there were two peaks. 5. (5) Depth profiles and measurement of chemical bonding showed that the implanted nitrogen combined with chromium to form Cr 2 N.

Surface modification of iron and steel by zirconium or yttrium ion implantation and their electrochemical properties

Abstract A study has been made of the corrosion behaviors of zirconium or yttrium ion implanted iron and Fe-5%Cr substrates, and of their surface characterization. Implantations of Zr + or Y + ions were carried out with fluences of around (0.1−1)×10 17 ions cm -2 at an energy of 100 keV at room temperature. The anodic dissolution behavior of ion-implanted iron or steel electrodes was measured by cyclic voltammetry in a pH 5 acetate buffer solution. Microscopic characterization of the implanted layers was performed by X-ray photoelectron spectroscopy (XPS) measurements combined with argon sputtering. Suppression of the anodic dissolution of iron is observed for both zirconium and yttrium implantations, and the former is more effective than the latter. It was also found that zirconium implantation into Fe-5%Cr alloys has a remarkable effect on the suppression of anodic dissolution. The suppression effects become clearer as the zirconium fluence increases. XPS results show that implanted zirconium atoms form a gaussian-like distribution, and in the case of high-fluence zirconium ion implantation, either carbon or oxygen atoms invaded near-surface layers to form a diffusion-like distribution. The binding energy spectra corresponding to C 1s and Zr 3d suggest that the invading carbon combines with iron to form iron carbides, and the invading oxygen combines with zirconium to form zirconium oxides. In conclusion, implanted zirconium atoms play an important role in the improvement in corrosion resistance of steels.

Densification of glassy carbon by fluorine ion implantation

Abstract A study has been made of the surface layer modification of glassy carbon (GC) by fluorine (F) ion implantation. F+-ion implantation into GC was performed at an energy of 150 keV with doses ranging from 5×1014 to 5×10 16 ions / cm 2 near room temperature. The changes in structure, composition and surface morphology of implanted specimens were examined by means of Raman spectroscopy (Raman), secondary ion mass spectrometry (SIMS) and atomic force microscopy (AFM), respectively. The Raman spectra for high fluences indicate the formation of amorphous carbon. The SIMS depth profiles of F-atoms are Gaussian-like distributions, and the peaks shift toward the surface as the fluence increases. The AFM measurements show that a step height of approximately 108 nm is observed at a fluence of 5×10 16 ions / cm 2 . From the results of peak shifts and step heights, it is concluded that F-ion implantation into GC induces a densification of the surface layer.

Synthesis of diamond-like carbon structure by Na-ion implantation in graphite and polyacetylene

A study has been made of the structures of diamond-like carbon by analyzing Raman spectra of ion-implanted carbon. Substrates used were glass-like carbon and high-density polyacetylene [HD-(CH) x ]. Sodium ion implantation was performed with doses of I ×10 15 -1×10 17 ions cm -2 at an energy of 150 keV. Raman spectra of glass-like carbon have two peaks at 1585 and 1360 cm -1 , which correspond to graphite (G-peak) and disordered graphite (D-peak), respectively. Ion implantation causes these two peaks to broaden, and finally, the Raman spectra show an asymmetric broad peak, showing the formation of diamond-like carbon. An intact polyacetylene has two Raman peaks around 1500 and 1150 cm -1 , which are due to the C=C stretching mode (v1) and a mixed mode (v3) of the CH bending and C-C single bond stretching vibration, respectively. Ion implantation in polyacetylene causes the appearance of two new peaks at 1360 and 1585 cm -1 , which seem to correspond to D-peak and G-peak, respectively. High-dose ion implantation causes the Raman spectrum to have an asymmetric broad peak that is almost the same as that observed from the ion-implanted glass-like carbon. From the variation of Raman spectra, it is concluded that the Raman spectrum with an asymmetric broad peak is composed of four components: G-peak, vl mode, D-peak and v3 mode. The relationship between wear resistance and Raman spectra will be discussed.

Annealing effects on luminescence from Ce-implanted α-Al2O3

Abstract A study has been made of the luminescence during 100 keV-Ar ion bombardment to Ce-implanted α-Al 2 O 3 at room temperature. Cerium ions were implanted into α-Al 2 O 3 single crystals at an energy of 100 keV at doses of 5×10 13 –1×10 16 ions / cm 2 . After ion implantation, annealing was carried out at 400°C, 600°C and 1000°C for 1 h in an argon gas atmosphere. Ion beam-induced luminescence was measured using Ar ion beam. The main peaks of the luminescence spectra emitted from Ce-implanted specimens appear near 340, 390 and 420 nm, which are the same wavelength of unimplanted specimen. In the case of as-implanted specimens, the intensity at 340 nm monotonously decreases as the dose increases, but those at 390 and 420 nm are maximum at the dose of 5×10 13 –2×10 14 ions / cm 2 . After annealing, the intensity at 340 nm is lower than or equal to that for an unimplanted specimen. In contrast, the peak intensities at 390 and 420 nm are higher for implanted and annealed specimens than for an unimplanted one. In conclusion, it is found that Ce implantation effects on luminescence appear at 390 and 420 nm.

Formation of carbon needles from fluoropolymer by ion irradiation followed by defluorination

Abstract A new carbon material with a unique surface has been created from polytetrafluoroethylene (PTFE) using a combination of ion irradiation and defluorination. In this study, the morphological change in the PTFE surface due to ion irradiation is observed in detail, and the mechanism of needle formation is investigated. At lower irradiation doses, hollows were formed, due to evaporation of PTFE. The number of hollows increased with dose, and the surface became covered with hollows and edges. Heating effects play an important role when the edges evolve into needles. The specimen covered with projections at a high density (3×10 5 mm −2 ) was placed in an evacuated glass tube with sodium metal, and kept at 473 K for 48 h. Because of the defluorination, the needles became conductive and could be observed by electron microscopy without using metal deposition. About 92% of the fluorine was eliminated by the reaction, and amorphous carbon needles were generated perpendicular to the target PTFE specimen.

Relationship between hydrogen content and magnetic properties of diamondlike carbon produced by the rf plasma-enhanced chemical vapor deposition method

Diamondlike carbon (DLC) films were prepared by the rf plasma-enhanced chemical vapor deposition method. The DLC films exhibited ferromagnetic behavior when prepared at 500 W, but diamagnetic behavior when prepared at 900 W. Electron spin resonance studies revealed that the spin density of the ferromagnetic specimen was much higher than that of the diamagnetic specimen. Although no significant difference was found in Raman and x-ray photoelectron spectroscopy studies, a difference in hydrogen content was revealed in elastic recoil detection analysis (ERDA) studies. It was found that the hydrogen content of the ferromagnetic DLC film was 30% higher than that of the diamagnetic film. The origin of the magnetization in the ferromagnetic film is therefore considered to be attributable to the difference in the hydrogen content.

X-ray photoelectron spectroscopy study of zirconium-implanted iron and carbon-implanted zirconium

Abstract A study has been made of the chemical bonding states of zirconium-implanted iron and carbon-implanted zirconium. Ion implantations were carried out at an energy of 100 keV with fluences of 5 × 1016 Zr ions cm-2 and 1.5 × 1016 C ions cm-2. The depth profile and chemical states of elements were investigated by X-ray photoelectron spectroscopy combined with Ar+ sputtering. In the case of zirconium implantation into iron oxide, the Zr 3d 5 2 peak observed on the surface appears at a binding energy of 181.9 eV. Considering this value and the binding energy of Fe 2p 3 2 spectra, zirconium on the surface seems to be bound to oxygen and iron. In the interior, the Zr 3d 5 2 peak shifts to 179.3 eV corresponding to Zr-C and the Fe 2p 5 2 peak also shifts to 706.6 eV corresponding to Fe-C. The binding energy of C 1s appears at 282.0 eV, which corresponds to an intermediate state between C-Fe and C-Zr. These chemical states of Zr, Fe and C indicate the formation of some complex states in implanted layers, associated with ZrxFeyCz.

Zirconium implantation into oxygen implanted iron

Abstract A study has been made of the influence of the iron surface oxide upon carbon incorporation in iron surface layers during Zr + implantation. Oxygen implanted iron was prepared by implantations of non-mass-analyzed oxygen ions into pure iron with acceleration voltages of 3,6 and 10 kV at room temperature. Zr + implantation into oxygen implanted iron was carried out at an energy of 100 keV with a fluence of 5×10 16 ions/cm 2 . The target temperature and the pressure during Zr + implantation were approximately room temperature and 3×10 −3 Pa, respectively. XPS and AES analyses were employed to characterize Zr + implanted layers. It was found that the carbon films were deposited by the combination of Zr + implantation with carbon adsorption, and the interface mixing between carbon films and iron surfacestook place by Zr + implantation. The depth profiles of carbon atoms near the interface between carbon film and iron showed that the incorporation of carbon atoms into iron substrates depended on iron oxide thickness: the C atoms were not invaded into the iron substrate as the surface oxide layers became thick.