T. Kamiya

Room temperature nanocrystalline silicon single-electron transistors

Single-electron transistors operating at room temperature have been fabricated in 20-nm-thick nanocrystalline silicon thin films. These films contain crystalline silicon grains 4 – 8 nm in size, embedded in an amorphous silicon matrix. Our single-electron transistor consists of a side-gated 20u200anm×20u200anm point contact between source and drain electrodes. By selectively oxidizing the grain boundaries using a low-temperature oxidation and high-temperature argon annealing process, we are able to engineer tunnel barriers and increase the potential energy of these barriers. This forms a “natural” system of tunnel barriers consisting of silicon oxide tissues that encapsulate sub-10 nm size grains, which are small enough to observe room-temperature single-electron charging effects. The device characteristics are dominated by the grains at the point contact. The material growth and device fabrication process are compatible with silicon technology, raising the possibility of large-scale integrated nanoelectronic sys...

Development of a new data collection system and chamber for microbeam and laser investigations of single event phenomena

Abstract A new target chamber and control system for temperature-based transient-IBIC and transient-LBIC measurements using the same experimental chamber is outlined. The system has been designed for both ultra-fast and relatively slow transient measurements as a function of temperature from 77 K to 450 K. The control system, implemented in the Labview environment, allows single ion scanning and transient acquisition on a set of oscilloscopes, for an array of temperatures and bias. The modularity of the system allows its use for a broad range of experiments from single event upset transient current measurements to scanning ion deep level transient spectroscopy charge transient measurements. In this paper, we describe the overall system and illustrate its potential by way of example.

Submicron microbeam apparatus using a single-ended accelerator with very high voltage stability

Abstract The JAERI light-ion microbeam apparatus for high-resolution ion beam analysis was constructed and installed on a beam line of 3 MV single-ended electrostatic accelerator with a high voltage stability of ± 1 × 10−5. In a performance test of the apparatus, the spot size of 0.4 × 0.4 μm2 in FWHM has been achieved so far by using 2 MeV helium ion beam with a target beam current of 77 pA. The light-ion microbeam apparatus and the accelerator system and the beam size measurement using 2 MeV helium ions is described. The ion beam optical design for submicron microbeam is also discussed.

TIARA electrostatic accelerators for multiple ion beam application

Abstract A unique electrostatic accelerators facility has been constructed mainly for application of multiple beam and microbeam to materials science research at JAERI Takasaki. The facility consists of a 3 MV single-ended accelerator with an extremely high voltage-stability of ± 1 × 10 −5 , a 3 MV tandem accelerator and a 0.4 MV ion implanter, which cover various ion particles in an energy range of 10 keV to 20 MeV. A voltage ripple of ± 1 × 10 −5 (60 V pp ) at 3 MV has been achieved for the single-ended machine. The performance of accelerators, beam lines and their applications to various research activities are outlined.

Sub-micron microbeam apparatus for high resolution materials analyses

The JAERI light-ion microbeam apparatus was constructed for high resolution materials analyses using PIXE, RBS or NRA with sufficient beam current. A minimum beam spot size of 0.3 μm with a beam current of 11 pA was obtained with a doublet quadrupole lens system. Simulation of the beam size and the brightness by using the second order beam optics calculation code shows that a beam size of 0.25 μm with a beam current 100 pA will be theoretically possible in our apparatus connected to an electrostatic accelerator having a voltage stability of 10−5 and with a energy analyzing system having an energy resolution of 10−5.

mubeam system for study of single event upset of semiconductor devices

Abstract A high energy heavy ion mubeam system has just been installed on a beam line of the 3 MV tandem electrostatic accelerator mainly for analysis of single event upset (SEU) of LSI memories in spacecraft. This system was designed for precise beam positioning at a desired muscopic area of the mucircuit, to experimentally evaluate of actual SEU sensitive area, and also to allow single ion hits for observing a transient charge pulse from an SEU. For these purposes, a fair amount of target beam current is required for beam positioning at the desired area. The system is equipped with two lens systems: one to control the target beam current in a wide range down to an extremely low current without any change of the beam optics, and the other to focus heavy ion beams within a spot size of 1 μm. The final goal is to hit a muscopic target area with a single 15 MeV nickel ion.

Effects of micro-beam induced damage on single-event current measurements

Abstract Radiation damage introduced by the impact of heavy-ion micro-beams has been studied in connection with its effects on single-event transient currents, which are measured by the digitizing sampling method combined with focused ion micro-beams. It is found that the single-event currents decrease with increasing the repetition number of measurements and that there exists a linear relationship between the ion fluence and the reciprocal of the normalized single-event charge. A single-event damage equation is deduced, where the damage constant is proportional to the defect density calculated using either the Kinchin-Pease model or the TRIM code. Experimental techniques are developed to eliminate the effect of radiation damage.

Development of a fast multi-parameter data acquisition system for microbeam analyses

Abstract A commercially available Personal Computer (PC)-based multi-parameter data acquisition system has been developed for ion microbeam analyses. The PC is equipped with a recent fast processor, a large volume of memory and a general multi-channel Analogue to Digital Converter (ADC) interface board. When a signal from an X-ray detector (PIXE), from a particle detector (RBS)or from others triggers this ADC for data acquisition. X-Y beam scanning control signals which indicate the beam position are also digitized at the same time. These data are addressed to the 3D matrices in the memory space, that consist of 1024 channels for the energy spectra and 150 × 150 pixels for corresponding the beam scan area. Real time data processing can be done in addition to this data acquisition by the fast processor with the large memory. Simultaneous PIXE and RBS elemental mapping and ion beam induced charge (IBIC) imaging on fine structure diodes have been demonstrated with this system.

A comparative study of the radiation hardness of silicon carbide using light ions

6H-silicon carbide (SiC) schottky diodes were irradiated at room temperature (RT) with proton, alpha and carbon particles to fluences in the range of 108–1013 ions/cm2. Both radiative and non-radiative traps are generated due to damage caused by the incident ions. Ionluminescence performed at RT revealed that radiative traps with photon emission energy of 2.32 eV appear after radiation. Electroluminescence measurement indicated that at RT the influence of non-radiative defects dominated over the radiative ones. Ion beam induced charge collection was used to investigate the charge collection efficiency of these diodes. Reduction in the charge pulse height is compared with calculation of non-ionising energy loss (NIEL). NIEL is a good measure of the displacement damage introduced in SiC materials by ionising particles. There is no significant difference in the radiation hardness of n-type and p-type 6H-SiC schottky diodes when irradiated with 2 MeV alpha particles.

Design of a focusing high-energy heavy ion microbeam system at the JAERI AVF cyclotron

Abstract For bio-medical applications of single-ion hit techniques such as radio-microsurgery, a focused high-energy heavy ion microbeam was designed and installed as a vertical beam line connected to the AVF cyclotron (K=110) facility at JAERI Takasaki. By extracting a heavy ion microbeam into atmosphere, living cells can be irradiated with an accuracy smaller than typical cellular sizes. In addition, a high-speed automatic targeting and single-ion irradiation system was combined with a two-dimensional microbeam scanning system allowing more than 1000 targets per minute to be hit within a set field of view. Such high speeds targeting is necessary when examining statistically significant trends in cell irradiation studies within feasible time constraints. A real-time single-ion hit position detecting system was also designed to further increase the reliability of such irradiations.