Asao Nakano

Evidence of Ga2Se3-Related Compounds on Se-Stabilized GaAs Surfaces

A Se-stabilized GaAs(001) surface is examined by extended X-ray absorption fine structure (EXAFS) analysis. The Se K-edge EXAFS shows components due not only to the first but also the second nearest neighbors, indicating that the Se atoms are incorporated into ordered atomic arrangements. Comparing the interatomic distances to those measured for Ga2Se3 and GaSe, it is concluded that the nature of the surface compound on the Se-stabilized GaAs surface is close to that of Ga2Se3.

Tailored heterointerface formation in InGaAs/InP superlattices by gas source migration-enhanced epitaxy

Abstract InGaAs/InP short period superlattices (SPSLs) with different interface atomic arrangements were grown by gas source migration-enhanced epitaxy (GSMEE) on (001)InP substrates. The local structure found around interfaces was investigated by P K-edge X-ray absorption fine structure (XAFS) using synchrotron radiation (SR), and by highly sensitive Raman scattering spectroscopy. Persistent reflection high-energy electron diffraction (RHEED) oscillations reveal that layer-by-layer nucleation can take place even during the growth of heterointerfaces by precise control of migration-enhanced epitaxy (MEE) sequences. The RHEED intensity traces of InGaAs/InP SPSLs without special characteristic shapes at the heterointerfaces were observed for the first time. XAFS analysis shows that the first nearest neighbors to P in the sample with InGa-P interfaces are In and Ga and that the first nearest neighbor in the sample with In-As interfaces is In. No clear GaP longitudinal optical (LO) phonon line is observed in the Raman scattering spectrum for SPSL with In-As interfaces, while a sharp and strong GaP LO phonon line is detected in SPSL with InGa-P interfaces.

Gas source molecular beam epitaxy and X-ray absorption fine structure characterization of InGaAs/InP short period superlattices

Abstract InGaAs/InP short period superlattices (SPSLs) were grown using gas source migration enhanced epitaxy (GSMEE) and using gas source molecular beam epitaxy (GSMBE) on (001)InP substrates. The local structure around the interfaces was investigated by Ga K-edge X-ray absorption fine structure (XAFS) using synchrotron radiation (SR). It was confirmed by the observation of persistent reflection high-energy electron diffraction (RHEED) oscillations that layer-by-layer nucleation takes place even during the growth of the heterointerfaces by precise control of migration enhanced epitaxy (MEE) sequences. XAFS analysis showed that the first nearest neighbor around Ga in the GSMEE grown sample with In-As interfaces is As, while those in the GSMBE grown sample are As and P. These results suggest that the atomically-controlled abrupt heterointerfaces can be obtained by GSMEE, whereas some intermixing of atoms at the heterointerfaces takes place in samples grown by GSMBE.

Xafs Study on Interfaces in III-V Semiconductor Heterostructures

Interfaces in InGaAs/InP heterostructures were investigated by XAFS analysis using synchrotron radiation. Two types of InGaAs/InP heterostructures were made by MEE using Ga, In, AsH 3 and PH 3 as sources. These InGaAs layers were terminated by (a) InGa and (b) As. The local structures around P were investigated by fluorescent XAFS analysis. It shows that the nearest neighbor around P is Ga and In in the InGa (a) sample and mainly In in the As (b) sample.

Structure of Chalcogen-Stabilized GaAs Interface

A photo chemical vapor deposited silicon dioxide - gallium arsenide interface treated by a selenium(Se)-molecular beam is investigated using extended X-ray absorption fine structure (EXAFS) analysis. The Se K-edge EXAFS shows the presence of Ga 2 Se 3 -related compound at the SiO 2 /GaAs interface, indicating that the Ga 2 Se 3 layer formed by the Se-treatment is preserved after the deposition of the SiO 2 film. The effective coordination number of the Se atoms is found to depend on the direction of the polarizing vector with respect to the crystal orientation. An attempt is made to interpret this dependence using a simple atomic layer model.

Crystallinity Analysis of Amorphous-Crystalline Mixed Phase Silicon Films Using EXAFS Method

The crystalline phase fraction (Xc) of amorphous-crystalline mixed phase Si films prepared by thermal annealing of a-Si:H films and by plasma CVD and chemical annealing methods was investigated by an EXAFS method. The EXAFS spectra of these films were represented by linear-combination of a-Si:H and c-Si EXAFS spectra. The values of Xc were analyzed by least-square curve fitting. Furthermore, the Xc values analyzed by a conventional Raman method were calibrated by the EXAFS analysis results.

Overview of IMS project; next generation environmental friendly soldering technology "EFSOT"

The 21st century can be called the era of the environment, and various efforts are being made to protect the global environment. For the materials used in the soldering of electronic circuits, there is also concern over the harmful effects of Pb, which is an important component of those materials, and so there is a trend to eliminate the Pb component. Under this background, and founded on the recognized importance of developing an alternative connection technology that has little environmental impact and harm, the IMS Project: Development of the Next Generation Environmental Friendly Soldering Technology began in June, 2000 in cooperation of industry and academia, and supported by the Ministry of Economy, Trade and Industry and the IMS (Intelligent Manufacturing Systems) Promotion Center. The project comprises four areas, which are evaluation of the impact of Pb-free soldering on the environment, evaluation of the safety of the metals with respect to living creatures, recycling technology, and the development of production technology. To achieve a worldwide consensus and application, the project is being internationalized.

Development of an X-Ray Diffractometer for Thin Film Analyses Applying a Compact X-ray Generator with High Loaded Power Rate to a Small Focus.

An X-ray diffractometer newly designed for thin film analyses is consisted of a compact X-ray generator with high loaded power rate to a small focus, a curved position sensitive detector and K-axis type 4-circle goniometer. The diffractometer enables measurements of thin film samples for electronic devices, e.g. rapid pole figure measurements of thin film samples and depth-sensitive measurements of multilayer thin films. A preffered orientation analysis of Co-Nb-Zr films for VTR core and a crystallinity analysis of multilayer films for circuit board were performed by using this apparatus.

Structural Study on Crystallization of a-Ge Using Exafs

Extended x-ray absorption fine structure (EXAFS) measurements were made on a-Ge and a-Ge:H films which were prepared by sputtering and were annealed at temperatures between 300 and 450° C.The first nearest neighbor distance and the Debye-valler factor were investigated. These values decrease rapidly on the crystallization of the samples. The relationship between them was analyzed in respect of tvo-body potential. The potential of amorphous state is considered to be affected by unharmonic term.