Wyniki wyszukiwania - Biblioteka Nauki

1

HAADF-STEM imaging and microscopy observations of heterostructures in electronic devices

100%

Shiojiri M.

Electron Technology : Internet Journal

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2004

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tom Vol. 36, nr 3

1-8

EN

Atomic resolved high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM), which has been widely used for the analysis of crystal and defect structures, is a quite new technique developed in this decade and its imaging mechanism is quite complicated. The first part of this paper is devoted to physics to understand HAADF-STEM imaging. Then, our recent investigations of GaN-based laser diodes are reviewed which were performed by HAADF-TEM and high-resolution field-emission scanning electron microscopy.

2

An application of cathodoluminescence microscopy on morphology of photosensitive dyes on AgBr crystals

63%

Saijo H. , Shiojiri M.

Electron Technology

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1998

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tom Vol. 31, No. 2

176-182

EN

Silver halides have been a unique material to record images in high qualty and with high sensitivity. However, the silver halides do not have enough sensitivity to exposing lighgt of green to red region. Photosensitive dyes adsorbed on silver halide microcrystals work to absorb light of the wavelength and inject photoelectrons to cause latent images in the substrates. This technique, spectral sensitization, is a key technology of modern photographic materials. Photosensitive dyes, generally cyanine dyes, assemble with their counter ions to form small crystallites, J-aggregates, on the surface of silver halide microcrystals. The incident electrons to the aggregates in an electron microscope produce photon emission, so-called cathodoluminescence (CL). The CL micrographs provided the information on shape, size, nucleation and growth, adsorptin position and perferential adsorption of J-aggregates on AgBr microcrystals. The results agreed well with those of Low-voltage High-resolution Scanning Electron Microscopy and Atomic Force Microscopy. The population of aggregates adsorbed on an AgBr particle varies from almost nine to full coverage. The thickness of J-aggregates crystallites is uniform and depends on a comgimation of dye species and counter ion, and is 2.1nm for thiacarbocyanine with sidium ion, 1.04 nm for thiacarbocyanine with tosyl ion and 0.5 nm for an oxacarbocyanine. However, the area of the crystallite increases with the number of dye molecules in it, and is about (20 ÷ 30)x(30 ÷ 50) nm. The longer edges of the crystallites align along [210] axes of the substrate surface. The crystallites connected linearly on the surface and stacked high to form multi-layered islands or arrays.

3

New specimen preparation methods for materials transmission electron microscopy using ion-milling

51%

Kawasaki M. , Yoshioka T. , Shiojiri M.

Electron Technology

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1998

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tom Vol. 31, No. 2

183-188

EN

Three mew preparation methods of specimen for transmission electron microscopy (TEM) applicable to materials characterization have developed using ion milling. One is an ion-digging method, where diamond powder particles are dispersed on the surface of specimen such as multilayer heterostructure and then the specimen are bombarded gy Ar ions perpendicular to its surface. Narrow poles with a diamond particle at the top form by ion digging, and can be observed in the surface profile by TEM. This method does not need the adhesion of two sliced substances and the mechanical polishing, which are troublesome pre-treatments used in conventional method. The others are preparation methods of selactions of powder particles, using photo-resistor Ni(P) elestroless plating for embedding the particles. These methods allow high-resolution TEM observations of micrometr-sized particles.

4

High-resolution transmission electron microscopy of AlAs/GaAs/AlGaAs multilayer heterostructure

51%

Nishio K. , Kątcki J. , Shiojiri M.

Electron Technology

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1999

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tom Vol. 32, No. 4

348-353

EN

A multilayer heterostructure of GaAs/AlAs/GaAs/AlGaAs/GaAs, which was prepared by molecular beam epitaxy at the Institute of Electron Technolgy was analysed by high-resolution transmission electron microscpoy (HRTEM) with the aid of image simulation and image processing. In spite of specimen damage during ion-milling Tem specimen preparation, columns of Ga and As atoms in the GaAs and columns of Al and As atoms in the AlAs were positioned in the (110) HRTEM images. The average and the variance of the widths of AlAs, GaAs, and AlGaAs layers were estimated from a small-ange scattering image reconstructed from the HRTEM image.

5

Investigations of materials in random-system by quantitative high-resolution transmission electron microscopy and electron diffraction

45%

Shiojiri M. , Endoh H. , Saijo H. , Isshiki T. , Nishio K.

Electron Technology

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1998

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tom Vol. 31, No. 2

189-192

EN

A detail of our project, "analysis of materials in random system by accurate measurement of high-resolution transmission electron microscopy (HRTEM) contrast and electron diffraction (ED) intensity" is reviewed. The main method is quantitative HRTEM and ED using an imaging plate (IP) recording and processing system, with the aid of the simulation and compresion. X-ray and neutron diffraction and cathodoluminescence scanning microscopy are also used as complementary methods. We have been making investigations on: 1) the local atomic configuration in cellular random system such as BaTi₂₋xSnFe₄O₁₁ and Fe-Al alloys, and the relation between their structure and magnetic properties; 2) the distribution of atoms at the heterointerfaces in multilayers such as GaAs/GaInP/Al-GaInP and GaAs/AlGaAs, and in polymorphic Zn(Mg)Se; 3) the site of doped Y atoms in BaTiO₃; 4) the structure and crystallization of elements and metal oxides in topological random system.

6

Investigation of the crystal and magnetic structures of polycrystalline materials by neutron and synchrotron radiation diffraction

45%

Przeniosło R. , Sosnowska I. , Fischer P. , Wróblewski T. , Shiojiri M.

Electron Technology

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1998

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tom Vol. 31, No. 2

147-151

EN

We describe we role of neutron and synchrotron radiation (SR) diffraction methods in the investigations of the crystal and magnetic structure of polycrystalline materials. Several examples of neutron and synchrotron radiation diffraction studies are presented. We discuss the structural properties of the following materials: cellular random system with magnetic spin-glass properties and manganite system with long range magnetic ordering at low temperatures.

7

High-resolution transmission electron microscopy and cathodoluminescence scanning electron microscopu observations of SrTiO₃-based varistors

45%

Shiojiri M. , Isshiki T. , Saijo H. , Sato S. , Hitomi A.

Electron Technology

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1998

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tom Vol. 31, No. 2

170-175

EN

(Sr₀.₃₅Ba₀.₃₅Ca₀.₃₀)₁.₀₂₆TiO₃ ceramic varistors, which were produced by sintering in different reducing ambiences and by reoxidizing, have been investigated by high-resolution electron microscopy, electron probe microanalysis, and cathodoluminescence (CL) scanning electron microscopy. Varistors produced by ordinary sintering Po₂=10⁻⁸ Pa, 1400°C, 2 h) have low varistor coefficient are compos4ed of well-developed crystalline grains with facet boundaries. A severe reducting treatment (Po₂=10⁻¹² Pa, 1100°C, 2 h), added in the sintering process, damages the crystallinity in the grains by introducing many oxygen vacancies and changes the boundary zone to amorphous-like microcrystallites, which causes high varistor coefficient favourable for practical use. CL images vizualize the oxygen vacancies in the grains and glassy segregate phase (SiO₂-BaO-MgO) at boundary among three grains. It is found that the surface layer, which is composed of bright enclosed by dark boundary zones in CL images, is responsible for the varistor property.

8

High-resolution electron microscopy and cathodoluminescence scanning electron microscopy of SrTiO3-based ceramics elucidating their varistor property.

38%

Shiojiri M. , Isshiki T. , Nishio K. , Saijo H. , Nomura T. , Hitomi A. , Sato S.

Inżynieria Materiałowa

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1998

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tom R. XIX, nr 4

779-784

EN

Semiconductive SrTiO3-based ceramics practically used as varistors and capacitors have been investigated using HRTEM, EDX and CLSEM. They were produced with and without an additonal reducing treatment at Po2=10 raising to a 12th power Pa in the sintering process at Po2=10 raising to a -8 power Pa, followed by reoxidizing process in the air. (Sr0.35Ba0.35Ca0.30)1.026TiO3 varistors produced without the additional heat-treatment are composed of well-developed crystalline grains with facet boundaries, having a low varistor coefficient (alpha<4). CL revealed that the grain, particularly near varistor surface, has high conductive inside containing oxygen vacancies and less-conductive boundary layer without the oxygen vacancies. The boundary layers may work as the double Shottky barriers. The additional reducing treatment forms a lot of oxygen vacancies in the grains of the varistors and damaged the crystallinity near the grain boundaries. The damaged regions easily introduce oxygen atoms into the grains during the reoxydizing process. The additional treatment, hence, produces thick boundary layers and consequently gives rise to high varistor coefficient (alpha>4), which is favourable for practical use. (Sr0.94Ba0.01Ca0.05)0.99TiO3 capacitors were also produced without the additional reducing treatment. Their grains have the facet boundary structure. The dielectric boundary layer and semiconductive inside of the grain are also observed. The boundary layer is as thin as a few ten nanometers, which cause the ceramic a high capacitance.

9

Investigation of III-V semiconductor heterostructures.

38%

Kątcki J. , Ratajczak J. , Adamczewska J. , Lewandowski W. , Rzodkiewicz W. , Shiojiri M. , Phillipp F.

Inżynieria Materiałowa

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1998

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tom R. XIX, nr 4

791-796

EN

In this paper an overview of analytical techniques necessary for characterization of the growth processes of III-V semiconductor heterostructures is given. The application of electron microscopic techniques as well as x-ray diffraction and photoluminescence is emphasized. The heterostructures discussed were grown by various techniques of epitaxy.

10

In situ obsevations of solid-solid reaction : decomposition of barium titanyl oxylate and formation of barium titanate

38%

Isshiki T. , Nishio K. , Shiojiri M. , Noguchi H. , Deguchi Y. , Yamamoto H.

Electron Technology

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1998

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tom Vol. 31, No. 2

202-207

EN

The thermal decomposition of BaTiO(C₂O₄)₂ 4H₂O and formation of BaTiO₃ were investigated by thermogravimetric analysis (TGA), differential thermal analysis combined with mass-spectroscopy (DTA-MS), high-temperature X-ray diffraction (XRD), and in situ scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TGA and DTA-MS showed that the dehydration occurred in a temperature range of 25 ÷ 240°C, followed by the decomposition of BaTiO(C₂O₄)₂ 4H₂O to BaCO₃, TiO₂, CO and CO₂ in a range of 240 ÷ 470°C. A porous structure showing the escape of CO and CO₂ gases was observed in an SEM image of a specimen at 400°C. Only diffuse peaks appeared in XRD charts in 200 ÷ 500°C, indicating that the BaCO₃ and TiO₂ are amorphous and/or micro-crystalline. XRD also disclosed that hexagonal BaTiO3 crystallites were formed by the solid-state reaction of the BaCO₃ and TiO₂ in range of 500 ÷ 650°C and then transformed to cubic crystals above 650°C. The direct formation of cubic BaTiO₃ crystals also occurred as a retareded reaction of the BaCO₃ and TiO₂ above 730°C.

11

TEM study of the formation of defects in AlGaAs/GaAs and InGaAs/GaAs heterostructures

38%

Kątcki J. , Ratajczak J. , Phillipp F. , Jin-Phillipp N. Y. , Shiojiri M. , Regiński K. , Bugajski M.

Electron Technology

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1999

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tom Vol. 32, No. 4

343-347

EN

In this paper the formation of lattice defects in AlGaAs/GaAs and InGaAs/GaAs heterostructures is discussed. The heterostructures were grown by various techniques of epitaxy. Transmission electron microscopy (TEM) observations of the heterostructure showed that in AlGaAs/GaAs heterostructures the main reason for the formation of defects are local inhomogeneties but in InGaAs/GaAs heterostructures lattice misfit is responible for this process.

12

Magnetization and structure of Fe-Al powders.

32%

Fujii M. , Saito K. , Wakayama K. , Kawasaki M. , Yoshioka T. , Isshiki T. , Nishio K. , Shiojiri M.

Inżynieria Materiałowa

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1998

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tom R. XIX, nr 4

860-863

EN

A few micrometers-sized Fe1-xAlx (x=0.35-0.42) powders prepared by atomizing method have the B2 structure and are paramegnetic. The powder milled for several hours is magnetized and has a spontaneous magnetization as great as 100 emu/g. The milled powder particles become flakes, which are composed of lamellae expanding parallel to the (110) plane and having heavily distorted lattice. High-resolution transmission electron microscopy and electron diffraction revealed that structures appear in very thin areas within the lamellae. These superlattices indicate the creation of large number of antiphase boundaries, which induce ferromagnetism. When the milled powder is heated at 100-400 degrees centigrade the magnetization decreases to a few tens emu/g, the lamella structures being kept.