Nano-layer structure of silicon-on-insulator materials

Silicon-on-insulator (SOI) has been recognized as a promising semiconductor starting material for ICs where high speed and low power consumption are desirable, in addition to its unique applications in radiation-hardened circuits. In the present paper, three novel SOI nano-layer structures have been demonstrated. ULTRA-THIN SOI has been fabricated by separation by implantation of oxygen (SIMOX) technique at low oxygen ion energy of 45 keV and implantation dosage of 1.81017/cm2. The formed SOI layer is uniform with thickness of only 60 nm. This layer is of crystalline quality. and the interface between this layer and the buried oxide layer is very sharp, PATTERNED SOI nanostructure is illustrated by source and drain on insulator (DSOI) MOSFETs. The DSOI structure has been formed by selective oxygen ion implantation in SIMOX process. With the patterned SOI technology, the floating-body effect and self-heating effect, which occur in the conventional SOI devices, are significantly suppressed. In order to improve the total-dose irradiation hardness of SOI devices, SILICON ON INSULATING MULTILAYERS (SOIM) nano-structure is proposed. The buried insulating multilayers, which are composed of SiOx and SiNy layers, have been realized by implantation of nitride and oxygen ions into silicon in turn at different ion energies, followed by two steps of high temperature annealing process, respectively, Electric property investigation shows that the hardness to the total-dose irradiation of SOIM is remarkably superior to those of the conventional SIMOX SOI and the Bond-and-Etch-Back SOI.

Design of high brightness cubic-GaN LEDs grown on GaAs substrate

The Principle of optical thin film was used to calculate the feasibility of improving the light extraction efficiency of GaN/GaAs optical devices by wafer-bonding technique. The calculated results show that the light extraction efficiency of bonded samples can be improved by 2.66 times than the as-grown GaN/GaAs samples when a thin Ni layer was used as adhesive layer and Ag layer as reflective layer. Full reflectance spectrum comparison shows that reflectivity for the incident light of 459.2 nm of the bonded samples was improved by 2.4 times than the as-grown samples, which is consistent with the calculated results.

Spatial variation of suspended particulate matter in the Yellow Sea

A joint oceanographic cruise between the Institute of Oceanography, Chinese Academy of Science and the Department of Oceanography, Seoul National University was carried out in the Yellow Sea during the summer of 1996 to investigate the concentration and particle-size distribution of suspended particulate matter (SPM). The general trends in the surface and bottom waters show that SPM concentrations and particle sizes decreased seawards in both the western (Chinese) and eastern (Korean) coastal regions of the Yellow Sea. In the bottom waters, SPM concentrations were higher and particle sizes were larger along the eastern coast than along the western coast. We suggest this is due to the resuspension of bottom sediments by strong onshore summer typhoons in the southwestern coastal waters of Korea.

Reproduction of algebraic structures by 16-18 year old students

In this exploratory research we analyze the structure sense evidenced by 33 secondary students (16-18 years old) in tasks requiring to reproduce the structure of given algebraic expressions. The expressions used were algebraic fractions related to algebraic identities. There were big differences between the students performance which allowed differencing levels in students´ structure sense. Questions and conjectures to be addressed in future research are presented.

Research in statistical education — planning of an international survey

As announced in the November 2000 issue of MathStats&OR [1], one of the projects supported by the Maths, Stats & OR Network funds is an international survey of research into pedagogic issues in statistics and OR. I am taking the lead on this and report here on the progress that has been made during the first year. A paper giving some background to the project and describing initial thinking on how it might be implemented was presented at the 53rd session of the International Statistical Institute in Seoul, Korea, in August 2001 in a session on The future of statistics education research [2]. It sounded easy. I considered that I was something of an expert on surveys having lectured on the topic for many years and having helped students and others who were doing surveys, particularly with the design of their questionnaires. Surely all I had to do was to draft a few questions, send them electronically to colleagues in statistical education who would be only to happy to respond, and summarise their responses? I should have learnt from my experience of advising all those students who thought that doing a survey was easy and to whom I had to explain that their ideas were too ambitious. There are several inter-related stages in survey research and it is important to think about these before rushing into the collection of data. In the case of the survey in question, this planning stage revealed several challenges. Surveys are usually done for a purpose so even before planning how to do them, it is advisable to think about the final product and the dissemination of results. This is the route I followed.

A methodological framework for studying policy coherence for development

The purpose of this article is to develop a methodological framework for analyzing Policy Coherence for Development (PCD). With this goal, we analyze different views of PCD in order to establish a comprehensive approach of Coherence adapted to globalization process. In this context, the article proposes a methodological framework based on four dimensions of analysis in CPD. In each dimen-sion, we set the areas and actors to investigate and we put forward research questions that could be use as a guide for a comprehensive approach to study PCD.