K. Fujii

PHOTOLUMINESCENCE OF CU+-DOPED SILICA GLASS PREPARED BY MEV ION IMPLANTATION

Abstract 2 MeV Cu + ions were implanted in silica glass at doses from 1xa0×xa010 15 to 1xa0×xa010 17 ions/cm 2 . Cu + -ion implanted silica glass followed by heat treatment showed photoluminescence due to monovalent copper ions. The photoluminescence intensity was the highest at a dose of 1xa0×xa010 16 Cu + ions/cm 2 in the present implantation condition. It was deduced that co-implantation of oxygen ions stabilizes the monovalent copper ions in silica glass.

Direct measurement and improvement of local soft error susceptibility in dynamic random access memories

Abstract Soft errors induced in a dynamic random access memory (DRAM) have been measured using a nuclear microprobe. Soft error susceptibility of the local position and structure to the soft error has been clarified. Collection efficiency of charge carriers, induced by incident ions on reverse biased p-n junctions with barrier well structures, has been verified for various implantation doses for well formation.

Well Structure by High-Energy Boron Implantation for Soft-Error Reduction in Dynamic Randam Access Memories (DRAMs)

The susceptibility against soft-errors in dynamic random access memories (DRAMs) has been evaluated using nuclear microprobes by monitoring various addresses of a memory cell array to determine the influence of upper wiring layers such as word lines, bit lines and other patterns. The correlations between irradiated positions of microprobes and monitored cell positions were discussed. The effect of buried implanted layers against carrier collection has also been investigated using ion-beam-induced-current (IBIC) measurement. IBIC measurement revealed that the retrograde well structure was more effective in suppressing soft errors than conventional well structures in bulk or epitaxial substrates.

Estimation of the Charge Collection for the Soft-Error Immunity by the 3D-Device Simulation and the Quantitative Investigation

The charge collection induced by incident particles was estimated by the 3-dimensional device simulation and the quantitative evaluation method using the nuclear microprobe. The role of the buried p +layer was well analyzed in terms of the soft-error immunity of DRAMs. The methods developed here are applicable to optimize the well structure for the soft-error immunity of advanced DRAMs.

Simultaneous mass-analyzed positive and negative low-energy ion beam deposition apparatus

Abstract We have developed a new concept low-energy ion beam deposition apparatus. This machine can generate mass-analyzed very low energy ion beams with positive and negative charges at the same time. It is possible to deposit these ions not only simultaneously but also alternatively. The name is Taotron and the nickname is PANDA (Positive And Negative-ions Deposition Apparatus). The aiming specifications of this apparatus are: (1) available positive ions are H, B, C, N, O, Si, Fe, etc. and negative ions are H, B, C, O, Si etc., (2) ion energy range covers 10 eV to 20 keV, (3) typical ion beam current is ≥ 10 μA (for 10 eV oxygen ions with both charges) and the beam size is ≥ 10 mm ⊘, (4) the base pressure of the deposition chamber is in the order of 10 −8 Pa and the pressure during deposition is in the order of 10 −6 Pa.

Preliminary experimental results on mapping of the elemental distribution of the organic tissues surrounding titanium-alloy implants

Abstract Titanium alloy (Ti 6Al 4V) is one of the most common materials which are used as orthopaedic and dental implants. In this paper, preliminary experimental results are presented on the measurement of distribution (mapping of X-ray intensities) of the constituent elements of the tissues as well as the released impurity elements in the organic tissues around a Ti-alloy implant. Micro-beam PIXE was carried out for the case of a Ti 6Al 4V implant which was inserted in tibial metaphysis of a rabbit for 12 weeks, using a Nissin high voltage accelerator. Maps of Ca and P clearly show the situation of bone formation and Ca concentration with respect to implant surface. The maps of Kα intensities of Ti and Al are also obtained to investigate the possible release of these elements. In conclusion, application of micro-beam PIXE to mapping of the constituent and impurity elements around implants can be used as a powerful tool in clarifying the mechamism of osseo-integration, and release of impurity ions from the implants.

Carbon nitride thin films formed by low energy ion beam deposition with positive and negative ions

Abstract Carbon nitride became an attractive system for the search of new functional materials since the existence of crystalline carbon nitride was predicted in 1989. Up to now the research in this field is focused mainly on the realization of the hexagonal phase of C3N4, whose properties have been proposed to be of low-compressibility, having a high thermal conductivity, a high optical band gap and insulating character. Ion beam deposition with mass analyzed positive and negative ions is a new technique for depositing thin films under well characterized conditions. With the Positive And Negative ion Deposition Apparatus (PANDA) the simultaneous deposition of low energy carbon and nitrogen ions under ultrahigh vacuum conditions is possible. Depositions were performed on silicon wafers under change of ion species and transport ratios. Rutherford backscattering was used as well as infrared and Raman spectroscopy in order to get compositional and structural information of the deposited thin films. The results are presented together with an overview of carbon nitride solids reported in the literature.

Formation process of CuCl nano-particles in silica glass by ion implantation

Abstract The formation process of CuCl crystals has been studied in (3 MeV 6xa0×xa010 16 Cl 2+ ions/cm 2 xa0+xa03 MeV 6xa0×xa010 16 Cu 2+ ions/cm 2 )-implanted silica glass by X-ray absorption spectroscopy and secondary ion mass spectroscopy. It was found from X-ray absorption spectroscopy that Cu atoms were mainly coordinated by oxygen atoms in as-implanted glass. Heat-treatment at 600°C caused the formation of Cu–Cl bonds and heat-treatment at 1000°C caused the formation of CuCl crystals in silica. It was deduced that the migration of Cl atoms is a rate-determining step for the formation of CuCl crystal, on the basis of the conventional precipitation model.

High energy resolution PIXE with high efficiency using the heavy ion microbeam

Abstract An X-ray crystal spectrometer using a position sensitive proportional counter combined with tandem microbeam line at Osaka National Research Institute have been developed. This system realizes high energy resolution PIXE analysis using a heavy ion microbeam (E

MICROPROBE PIXE ANALYSIS OF ALUMINIUM IN THE BRAINS OF PATIENTS WITH ALZHEIMER'S DISEASE

To investigate the cause of Alzheimers disease (senile dementia), we examined aluminium (Al) in the rat liver, and in the brains (hippocampus) of Alzheimers disease patients using heavy ion (5 MeV Si3+) microprobe and proton (2 MeV) microprobe PIXE analysis. Heavy ion microprobes (3 MeV Si2+) have several times higher sensitivity for Al detection than 2 MeV proton microprobes. (1) In the rat liver, Al was detected in the cell nuclei, where phosphorus (P) was most densely distributed. (2) We also demonstrated Al in the cell nuclei isolated from Alzheimers disease brains using heavy ion (5 MeV Si3+) microprobes. Al spectra were detected using 2 MeV proton microprobes in the isolated brain cell nuclei. Al could not be observed in areas where P was present in relatively small amounts, or was absent. Our results indicate that Alzheimers disease is caused by irreversible accumulation of Al in the nuclei of brain cells.