Yoshiaki Agawa

Structural and Physical Characteristics of Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films Deposited Using a Coaxial Arc Plasma Gun

Ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) films were formed without initial nucleation using a coaxial arc plasma gun. The UNCD crystallite diameters estimated from the X-ray diffraction peaks were approximately 2 nm. The Fourier transform infrared absorption spectrum exhibited an intense sp3-CH peak that might originate from the grain boundaries between UNCD crystallites whose dangling bonds are terminated with hydrogen atoms. A narrow sp3 peak in the photoemission spectrum implied that the film comprises a large number of UNCD crystallites. Large optical absorption coefficients at photon energies larger than 3 eV that might be due to the grain boundaries are specific to the UNCD/a-C:H films.

Medium energy ion scattering using a toroidal analyzer combined with a microbeam line

Abstract A microbeam line with a toroidal electrostatic analyzer was constructed for medium energy ion scattering by a focused beam. Demagnification factors of the lens system were Dx = 0.99 and Dy = 2.1 for the present two-chamber configuration and Dx = 2.4 and Dy = 7.1 for the future single chamber configuration. For a 200 keV He+ beam, the energy resolution of the toroidal analyzer was d E E = 4.7 × 10 −3 , corresponding to a depth of 6.4 A in a surface gold layer.

A 500 keV ion beam accelerator for microbeam formation

Abstract A 500 keV ion accelerator with a Disktron high-voltage generator has been developed for RBS analysis with microbeam and ion beam modification. An accelerating voltage stability of better than 4.5 × 10−4, with a long-term (∼1 h) current stability of better than 3%, was obtained for both proton and helium ions at 400 keV. The short-term (∼ ms) current stability, which is very important for RBS mapping measurements, was found to be better than 2 × 10−3. The X-ray dose rate around the accelerator was less than 0.03 mR/h at maximum with an acceleration of helium ions of 40 μA at an energy of 500 keV.

A high current sheet plasma ion source

Abstract A cylindrical solid beam has great disadvantages in high current, high energy ion implantation. These disadvantages are poor heat dissipation, nonuniformity of the beam itself and difficulty of irradiation on large area samples. A sheet ion source and an irradiation system have been developed, in which beltlike samples could be run perpendicular to a sheet ion beam. The design and operation principles are reported.

Influence of beam current fluctuation on secondary electron and RBS mapping images

Abstract Secondary electron images obtained by fast beam scanning were degraded by a microbeam current fluctuation of more than 1% in the millisecond range, giving rise to difficulties in minimizing the beam spot. Multiple iteration of mapping improved the image, while an increase in the time-constant for the secondary electron signal processing, which smoothed the signal fluctuation induced by ion beams, could not improve the image. Rutherford backscattering images were less sensitive to the beam fluctuation and were not greatly degraded by a beam fluctuation of up to 50%.

Electrostatic accelerators with high energy resolution

Abstract Several models of electrostatic accelerators based on rotating disks (Disktron) have been manufactured for various ion beam applications like surface analyses and implantation. The high voltage terminal of the Disktron with a terminal voltage of up to 500 kV is open in air, while the generator part is enclosed in FRP (fiber reinforced plastics) or a ceramic vessel filled with sf 6 gas. The 1 MV model is completely enclosed in a steel vessel. A compact tandem accelerator of the pellet chain type with a terminal voltage of 1.5 MV has also been manufactured. The good energy stability of these accelerators, typically in the range of 10 −4 , has proved to be quite favorable for applications in precise studies of material surfaces, including the use of microbeam techniques.

A 500 keV ion accelerator with two types of ion source

Abstract A 500 keV ion accelerator system equipped with a DISKTRON high voltage generator and two types of ion source has been developed to provide ion beams for RBS analysis with microbeams and surface modification. H + and He + beams focused to less than 1 μm with a voltage stability of less than 10 −4 have been obtained in a microbeam line. P + As + and other heavy ion beams of sufficient intensity for surface modification are also obtained. Uniformities of P + and As + ions implanted into a 2 in. Si wafer were evaluated to be 1.5% and 1.2%, respectively.

The development of a 400 keV ion accelerator for surface study and atomic collision experiments

Abstract Two types of 400 keV ion accelerators have been developed for surface study and atomic collision experiments. The features of the systems are: (1) extremely stable accelerating voltage, (2) low emittance of the beam, (3) a very low X-ray dose rate, and (4) compact design. The beam optics of the systems are explained and the method of the energy calibration is described. Then their performance and the application are reported.

Influence of Beam Current Ripple on Secondary Electron and RBS Mapping Images

The influence of beam current ripple on Rutherford backscattering (RBS) and secondary electron mapping images using 400 keV He+ ion beams with a beam spot size of about 1 µm has been investigated to clarify the degradation of mapping images due to the current fluctuation. It was found that the secondary electron mapping images were deteriorated by a beam fluctuation of more than a few percent, while the RBS mapping image was rather insensitive to fluctuations of up to 50%.

Negative ion source for the tandem accelerator

A sheath rod type negative ion source of the duoplasmatron is designed for a tandem accelerator. The accelerator is of the pellet chain type, which can provide a terminal voltage of 1.5 MV and a current of 500 μA. For the ion source it can be found that the current of the negative (H) ion beam depends on the gas flow rate, and the position of the sheath rod between the anode and the intermediate electrode. A negative (H−) ion current of 8 μA is obtained when an extraction voltage of 15 kV is applied.