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The graphite surfaces were irradiated by Ar+ ions with and without a simultaneous Co supply at room temperature. The sputtered surface without Co supply was characterized by densely distributed conical protrusions with aligned carbon nanofibers (CNFs) on the tops, whereas Ar+-bombarded surfaces with a simultaneous Co supply were covered with asparagus-like (micrometer order in base diameter) or nanofibrous (10–50 nm in diameter) structures depending on the supply rate of Co atoms. No CNF-tipped cones were observed to form. For the nanofibers containing carbon and cobalt, the hysteresis behavior observed in the magnetization property by applying magnetic fields in directions perpendicular and parallel (in-plain) to the substrate was almost identical, whereas a continuous 1 µm thick-Co film showed the strong in-plane anisotropy. Other materials could be readily incorporated into CNFs by choosing the suitable metal sources. Thus, the ion-irradiation method is expected to open up a new approach to fabricate ferromagnetic 1-D nanomaterials at room temperature.

The pulsed ESR technique was employed in the present study to obtain the spin-spin relaxation times of the E 1 ′ center (an unpaired electron at an oxygen vacancy) in natural quartz with and without irradiation. The relaxation times of the heat treated E 1 ′ center in natural unirradiated quartz of a granite and of uranium ore were 3.5– 7.1 μ s . Electron and gamma ray irradiated quartz showed the relaxation times of 7.1– 15.7 μ s while He ion implanted quartz showed 1.0– 2.0 μ s , much less than the other samples. The intensity of the E 1 ′ center increased in stepwise heating up to 300 ∘ C before decreasing above that temperature except for He implanted sample which showed monotonic decrease on heating. The present experimental results showed that the characteristics of the E 1 ′ center created by high linear energy transfer (LET) radiation is different from that by low LET radiation, suggesting that, in nature, the oxygen vacancies are created by low LET radiation, i.e. external beta and gamma rays, rather than by alpha particles and alpha recoil nuclei.

Junction properties of Al/high-conductivity layer (HCL) near the surface of hydrogenated homoepitaxial diamond films were re-examined to evaluate the published models for the origin of HCL. As compared with the junction properties of metal/oxidized B-doped diamond films, it is confirmed that carrier transport in the Al/HCL junction can be well explained by the conventional Schottky barrier theory for metal/p-type semiconductors. This means that the carrier depletion region of HCL (i.e. the downward band bending for p-type HCL) actually exists in the vicinity of the Al/HCL junction at thermal equilibrium (zero bias) as well as at reverse bias conditions. To keep the downward band bending of HCL, ionized acceptors must exist in this region. We discuss a downward band-bending model based on the hydrogen-related shallow acceptors to explain electrochemical behaviors (adsorbate effect) of HCL as well as the present Schottky junction properties.

We studied the misorientation angle dependence of the surface morphology in homoepitaxial diamond film grown by the microwave plasma chemical vapor deposition (CVD) method using an extremely low CH4 concentration gas system (less than 0.15% CH4/H2 ratio). We found that, for a misorientation angle (θoff) of less than 1°, the surfaces of diamond films are atomically flat surface. Their mean roughness (Ra) determined by atomic force microscopy (AFM) is less than 0.04 nm. Ra subsequently increases as θoff increases above θoff>1.5°. This tendency is opposite to that of the conventional homoepitaxial growth using a high CH4/H2 ratio. We also found that the θoff dependence of Ra of surfaces formed by hydrogen (H2) plasma etching has the same tendency as that of the CVD growth at the low CH4/H2 ratio mentioned above. Specifically, Ra is less than 0.17 nm for θoff

Gas cluster ion beam techniques have been developed for atomic and molecular level surface modification processing. Shallow implantation, high yield sputtering, surface smoothing, and low damage surface cleaning have been demonstrated experimentally. This article reports recent results concerning surface treatments that are distinctly different from those produced by conventional monomer ion irradiation. Possible applications of gas cluster ion beam processing to new areas of surface modifications are suggested.