Takeo Tanaka

Annular pupils for electron optics were produced using a focused ion beam (FIB), enabling an increase in the depth of focus and allowing for aberration-free imaging and separation of the amplitude and phase images in a scanning transmission electron microscope (STEM). Simulations demonstrate that an increased focal depth is advantageous for three-dimensional tomography in the STEM. For a 200 kV electron beam, the focal depth is increased to approximately 100 nm by using an annular pupil with inner and outer semi-angles of 29 and 30 mrad, respectively. Annular pupils were designed with various outer diameters of 40-120 mu m and the inner diameter was designed at 80% of the outer diameter. A taper angle varying from 1 degrees to 20 degrees was applied to the slits of the annular pupils to suppress the influence of high-energy electron scattering. The fabricated annular pupils were inspected by scanning ion beam microscopy and scanning electron microscopy. These annular pupils were loaded into a STEM and no charge-up effects were observed in the scintillator projection images recorded by a CCD camera. (C) 2011 Elsevier B.V. All rights reserved.

Annular pupils for electron optics were produced using a focused ion beam (FIB), enabling an increase in the depth of focus and allowing for aberration-free imaging and separation of the amplitude and phase images in a scanning transmission electron microscope (STEM). Simulations demonstrate that an increased focal depth is advantageous for three-dimensional tomography in the STEM. For a 200 kV electron beam, the focal depth is increased to approximately 100 nm by using an annular pupil with inner and outer semi-angles of 29 and 30 mrad, respectively. Annular pupils were designed with various outer diameters of 40-120 mu m and the inner diameter was designed at 80% of the outer diameter. A taper angle varying from 1 degrees to 20 degrees was applied to the slits of the annular pupils to suppress the influence of high-energy electron scattering. The fabricated annular pupils were inspected by scanning ion beam microscopy and scanning electron microscopy. These annular pupils were loaded into a STEM and no charge-up effects were observed in the scintillator projection images recorded by a CCD camera. (C) 2011 Elsevier B.V. All rights reserved.

Annular pupils for electron optics were developed using a focused ion beam (FIB) technique to realize an increase in the depth of focus, aberration-free imaging and separation of amplitude and phase images under scanning transmission electron microscopy (STEM). A tantalum plate 30 pm thick was used as the annular pupil material in the present experiment. The annular pupils were designed with various outer diameters from 120 pm to phi 40 mu m. The inner diameter was designed at 60 to 80% of the outer diameter. The fabricated annular pupils were inspected by scanning ion beam microscopy and scanning electron microscopy. Annular pupils were successfully obtained at the designed size, although the slits of the pupils were slightly tapered by the ion beam etching process. These annular pupils were loaded on a STEM and confirmed to display no charge-up phenomenon by observation of the projection image on a scintillator using a CCD camera. We confirmed the image taken by annular pupil with narrow width was able to suppress the influence of the normal illumination. (C) 2008 Elsevier Ltd. All rights reserved.

Annular pupils for electron optics were developed using a focused ion beam (FIB) technique to realize an increase in the depth of focus, aberration-free imaging and separation of amplitude and phase images under scanning transmission electron microscopy (STEM). A tantalum plate 30 pm thick was used as the annular pupil material in the present experiment. The annular pupils were designed with various outer diameters from 120 pm to phi 40 mu m. The inner diameter was designed at 60 to 80% of the outer diameter. The fabricated annular pupils were inspected by scanning ion beam microscopy and scanning electron microscopy. Annular pupils were successfully obtained at the designed size, although the slits of the pupils were slightly tapered by the ion beam etching process. These annular pupils were loaded on a STEM and confirmed to display no charge-up phenomenon by observation of the projection image on a scintillator using a CCD camera. We confirmed the image taken by annular pupil with narrow width was able to suppress the influence of the normal illumination. (C) 2008 Elsevier Ltd. All rights reserved.

A parallel image detection and image processing system for scanning transmission electron microscopy was developed using a multidetector array consisting of a multianode photomultiplier tube arranged in an 8x8 square array. The system enables the taking of 64 images simultaneously from different scattered directions with a scanning time of 2.6 s. Using the 64 images, phase and amplitude contrast images of gold particles on an amorphous carbon thin film could be separately reconstructed by applying respective 8 shaped bandpass Fourier filters for each image and multiplying the phase and amplitude reconstructing factors. (c) 2007 American Institute of Physics.

A parallel image detection and image processing system for scanning transmission electron microscopy was developed using a multidetector array consisting of a multianode photomultiplier tube arranged in an 8x8 square array. The system enables the taking of 64 images simultaneously from different scattered directions with a scanning time of 2.6 s. Using the 64 images, phase and amplitude contrast images of gold particles on an amorphous carbon thin film could be separately reconstructed by applying respective 8 shaped bandpass Fourier filters for each image and multiplying the phase and amplitude reconstructing factors. (c) 2007 American Institute of Physics.

Hafnium oxide thin films were prepared using a high-energy ion beam assisted deposition (IBAD) system. Oxygen ion energy was varied the range of 1-20 keV, which is much wider than those in other IBAD works. The transport ratio (TR), defined as the ratio between the hafnium arrival rate and the oxygen ion dose, was varied at 1 and 10. The substrate was cooled by water. The structures of the films were characterized using X-ray diffraction and the morphology of films was observed by field emission scanning electron microscope. In this research, films with cubic, tetragonal and monoclinic structures, or their mixtures were obtained, and their structures were dependent on ion beam energy and TR. (C) 2003 Elsevier Science B.V. All rights reserved.

Hafnium oxide thin films were prepared using a high-energy ion beam assisted deposition (IBAD) system. Oxygen ion energy was varied the range of 1-20 keV, which is much wider than those in other IBAD works. The transport ratio (TR), defined as the ratio between the hafnium arrival rate and the oxygen ion dose, was varied at 1 and 10. The substrate was cooled by water. The structures of the films were characterized using X-ray diffraction and the morphology of films was observed by field emission scanning electron microscope. In this research, films with cubic, tetragonal and monoclinic structures, or their mixtures were obtained, and their structures were dependent on ion beam energy and TR. (C) 2003 Elsevier Science B.V. All rights reserved.

Boron nitride films with Ti added (BN:Ti) were prepared by a dual-ion beam sputtering method. The properties of the films were investigated by Fourier transform infrared spectrophotometer (FT-IR), electron spectroscopy for chemical analysis, X-ray diffractometer and the nano-indentation method. The structure of the BN:Ti films changed from the cubic phase to the hexagonal phase at more than 14.8 at.% added Ti. The internal stress and hardness decreased with an increase in the Ti content. With the reduction of the internal stress, the FT-IR absorption bands near 1100 cm(-1) related to the cubic boron nitride phase changed to lower wavenumber. Added Ti atoms formed TiB2 and TiN in the films with a small amount of Ti content, but with increasing Ti content, mainly TiN was formed. (C) 2002 Elsevier Science B.V. All rights reserved.

Boron nitride films with Ti added (BN:Ti) were prepared by a dual-ion beam sputtering method. The properties of the films were investigated by Fourier transform infrared spectrophotometer (FT-IR), electron spectroscopy for chemical analysis, X-ray diffractometer and the nano-indentation method. The structure of the BN:Ti films changed from the cubic phase to the hexagonal phase at more than 14.8 at.% added Ti. The internal stress and hardness decreased with an increase in the Ti content. With the reduction of the internal stress, the FT-IR absorption bands near 1100 cm(-1) related to the cubic boron nitride phase changed to lower wavenumber. Added Ti atoms formed TiB2 and TiN in the films with a small amount of Ti content, but with increasing Ti content, mainly TiN was formed. (C) 2002 Elsevier Science B.V. All rights reserved.

A systematic study on thermoluminescence (TL) and thermally stimulated exoelectron emission (TSEE) has been performed for CaF2/CaO dual phases doped individually with all the fourteen available lanthanide oxides, to investigate their TL and TSEE emissivities for the UV and X-ray irradiations. A newly developed apparatus has allowed both the TL and the TSEE to be measured simultaneously, leading to finding a different aspect between the TL and TSEE emissivities. The result clearly indicates that Tb4O7 and Yb2O3 are the most promising lanthanide oxides to be doped in CaF2/CaO. The Tb4O7 leads a double peaked TL glow spectrum below 500 K for UV-light irradiation and the Yb2O3 leads a very intensive single peak of TL glow spectrum around 630 K for X-raps revealing its excellent characteristics of practical use for TL dosimetry. For TSEE dosimetry, La2O3, Tm2O3 and Yb2O3 are also promising for X-rays, and Gd2O3 and Lu2O3 for UV rays as well. The intensities of TL glow and TSEE emission from CaF2/CaO:Tb4O7 depend strongly on quenching rate of the sample during the cooling process of sintering. The TL glow shows the superlinear behavior against the dose of UV rays.

A systematic study on thermoluminescence (TL) and thermally stimulated exoelectron emission (TSEE) has been performed for CaF2/CaO dual phases doped individually with all the fourteen available lanthanide oxides, to investigate their TL and TSEE emissivities for the UV and X-ray irradiations. A newly developed apparatus has allowed both the TL and the TSEE to be measured simultaneously, leading to finding a different aspect between the TL and TSEE emissivities. The result clearly indicates that Tb4O7 and Yb2O3 are the most promising lanthanide oxides to be doped in CaF2/CaO. The Tb4O7 leads a double peaked TL glow spectrum below 500 K for UV-light irradiation and the Yb2O3 leads a very intensive single peak of TL glow spectrum around 630 K for X-raps revealing its excellent characteristics of practical use for TL dosimetry. For TSEE dosimetry, La2O3, Tm2O3 and Yb2O3 are also promising for X-rays, and Gd2O3 and Lu2O3 for UV rays as well. The intensities of TL glow and TSEE emission from CaF2/CaO:Tb4O7 depend strongly on quenching rate of the sample during the cooling process of sintering. The TL glow shows the superlinear behavior against the dose of UV rays.

The DV-Xa molecular orbital (MO) calculation method has been applied to the carbon K-V X-ray emission spectra of graphite. The calculated 2p density of states (DOS) of a larger model cluster, which avoided the influence of dangling bonds of the cluster edge, was in excellent agreement with the X-ray emission spectra, The calculated pi and a subbands of 2p DOS explained the polarized behavior of the spectra. The orientation of graphite was quantitatively discussed by means of polarization of the spectra. These results were applied to the analysis of the structural change of mechanical milled graphite; the structure change of the ball-milled graphite was studied by the X-ray spectroscopy and MO calculation. It was shown that the refinement of graphite powder occurred for up to 1000 h of milling, keeping the graphite structure, and that a further milling changed the C-C bonding within the graphite layer network. (C) 1999 Elsevier Science B.V. All rights reserved.

The DV-Xa molecular orbital (MO) calculation method has been applied to the carbon K-V X-ray emission spectra of graphite. The calculated 2p density of states (DOS) of a larger model cluster, which avoided the influence of dangling bonds of the cluster edge, was in excellent agreement with the X-ray emission spectra, The calculated pi and a subbands of 2p DOS explained the polarized behavior of the spectra. The orientation of graphite was quantitatively discussed by means of polarization of the spectra. These results were applied to the analysis of the structural change of mechanical milled graphite; the structure change of the ball-milled graphite was studied by the X-ray spectroscopy and MO calculation. It was shown that the refinement of graphite powder occurred for up to 1000 h of milling, keeping the graphite structure, and that a further milling changed the C-C bonding within the graphite layer network. (C) 1999 Elsevier Science B.V. All rights reserved.

Ball-milling of graphite powder was performed by the use of a stainless steel ball-mill and an agate ball-mill. The crystal structure of the ground graphite was studied by transmission electron microscopy and X-ray diffractometry. A spectrometric approach to the change of structure during the milling process was also carried out by the carbon Kα X-ray-emission band spectroscopy (XES). The carbon Kα XES spectra were compared with those of carbon materials such as ball-milled diamond powder, i-diamond film and amorphous carbon powder. In the case of the stainless steel ball-milling, microcrystalline and/or onion-like structure were formed. The XES spectrum suggested that sp3 hybrid orbital was formed after 2000 h of milling. While, in the case of an agate ball-milling, it was suggested that the 2p orbital became narrow as a result of further finely-ground pulverization of graphite crystallite after 1750 h of milling.

Ball-milling of graphite powder was performed by the use of a stainless steel ball-mill and an agate ball-mill. The crystal structure of the ground graphite was studied by transmission electron microscopy and X-ray diffractometry. A spectrometric approach to the change of structure during the milling process was also carried out by the carbon Kα X-ray-emission band spectroscopy (XES). The carbon Kα XES spectra were compared with those of carbon materials such as ball-milled diamond powder, i-diamond film and amorphous carbon powder. In the case of the stainless steel ball-milling, microcrystalline and/or onion-like structure were formed. The XES spectrum suggested that sp3 hybrid orbital was formed after 2000 h of milling. While, in the case of an agate ball-milling, it was suggested that the 2p orbital became narrow as a result of further finely-ground pulverization of graphite crystallite after 1750 h of milling.

The reduction of crystalline size and amorphization of graphite and diamond during agate and stainless ball-milling are investigated by Raman spectroscopy. The ultimate crystalline size of,graphite, estimated by the Raman intensity ratio, of 2.5 nm for the agate ball-mill is smaller than that of 3.5 nm for the stainless ball-mill, while the milling time to reach the ultimate size for the former is about 10 times larger than for the latter, indicating more stability of the nanocrystalline graphite. After reaching the ultimate crystalline size, a significant broadening of the Raman spectra, which indicates the completion of amorphization, is detected only for the stainless ball-milled graphite at similar to 500 h of milling. Also the increase rate of the Raman peakwidth for the stainless ball-milled graphite before amorphization is higher than that for the agate ball-milled graphite, indicating a larger introduction of disorder from the start of milling. Amorphization of diamond is also observed for the stainless ball-mill. The difference in the results between the agate and the stainless ball-mill is discussed in terms of the effect of impurity mixed from the milling apparatus on the stability of nanocrystalline carbon materials.

The reduction of crystalline size and amorphization of graphite and diamond during agate and stainless ball-milling are investigated by Raman spectroscopy. The ultimate crystalline size of,graphite, estimated by the Raman intensity ratio, of 2.5 nm for the agate ball-mill is smaller than that of 3.5 nm for the stainless ball-mill, while the milling time to reach the ultimate size for the former is about 10 times larger than for the latter, indicating more stability of the nanocrystalline graphite. After reaching the ultimate crystalline size, a significant broadening of the Raman spectra, which indicates the completion of amorphization, is detected only for the stainless ball-milled graphite at similar to 500 h of milling. Also the increase rate of the Raman peakwidth for the stainless ball-milled graphite before amorphization is higher than that for the agate ball-milled graphite, indicating a larger introduction of disorder from the start of milling. Amorphization of diamond is also observed for the stainless ball-mill. The difference in the results between the agate and the stainless ball-mill is discussed in terms of the effect of impurity mixed from the milling apparatus on the stability of nanocrystalline carbon materials.

Mechanical alloying (MA) has been performed for a mixture of elemental iron and graphite powders by the conventional type ball-mill. Solid state reaction of Fe₃C formation has been studied for Fe₈₃C₁₇, Fe₇₅C₂₅ and Fe₇₁C₂₉ powders by transmission electron microscopy, X-ray diffractometry, ⁵⁷Fe Mössbauer spectroscopy and differential scanning calorimetry. The amorphous phase coexistent with α-Fe has been formed after 200 hour MA. After subsequent milling, these phases have been transformed into Fe₃C carbide through Fe₇C₃-like carbide. While, the successive reaction from Fe₅C₂ to Fe₃C has been also confirmed in the process of heating the amorhous phase coexistent with α-Fe.

Mechanical alloying (MA) and mechanical grinding (MG) have been performed for Fe₈₆C₁₄ powders by a conventional ball-mill. MA has been carried out on a mixture of elemental iron and graphite powders and MG on a pre-alloyed iron-cementite powder. Ball-milled powders have been examined by scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, ⁵⁷Fe Mössbauer spectroscopy and differential scanning calorimetry. Super-saturated solid solution of α-iron has been formed by a cold-welding of the pulverized iron particles on the MA process. By subsequent milling and/or heating, carbide has been formed from the solid solution. While, ultra-fine structure with capital size of few nano-meter has been formed for MG powder of the white cast iron. Amorphous phase has been formed by both MA and MG.