Jun-Young Oh

Microstructural properties and dislocation evolution on a GaN grown on patterned sapphire substrate: A transmission electron microscopy study

The microstructural properties of a GaN layer grown on a patterned sapphire substrate (PSS) were studied in detail using transmission electron microscope techniques to determine dislocation and growth behaviors. Regular and uniform recrystallized GaN islands were observed on the protruding pattern. On a flat sapphire surface, the crystallographic orientation relationship of ⟨1¯21¯0⟩GaN on FS//⟨11¯00⟩sapphire and {11¯01}GaN on FS//{12¯13}sapphire existed between the GaN and the substrate. On the other hand, the orientation relationship of ⟨1¯21¯0⟩GaN layer//⟨1¯21¯0⟩GaN island on IS//⟨11¯00⟩sapphire and {11¯01}GaN layer//{0002}GaN island on IS//{12¯13}sapphire was confirmed among the GaN layer, the recrystallized GaN islands on an inclined sapphire surface and the PSS. The flat surface among the protruding patterns began to fill rapidly with GaN. Then, the GaN gradually overgrew the protruding pattern and coalesced near the summit as the growth time increased. The generation of threading dislocations was ob...

High-resolution transmission electron microscopy study on the growth modes of GaSb islands grown on a semi-insulating GaAs (001) substrate

The initial growth behaviors of GaSb on a GaAs substrate were studied using a high-resolution electron microscope (HRTEM). Four types of GaSb islands were observed by HRTEM. HRTEM micrographs showed that strain relaxation mechanisms were different in the four types of islands. Although 90° misfit dislocations relieve misfit strain in the islands, additional mechanisms are required to relax the remaining strain. The existence of elastic deformation near the surface related to dislocations and intermediate layers between GaSb and GaAs were demonstrated in island growths. Finally, the generation of planar defects to relieve strain was observed in a specific GaSb growth.

Understanding Scientific Inference in the Natural Sciences Based on Abductive Inference Strategies

The purpose of this study is to understand scientific inference in the natural sciences through the use of abductive inference. Abductive inference enables scientific discovery through creative inference during problem solving. We present the following two research problems: (1) the validity of a scientific inference procedure building on Magnani’s research (2001) that employs various strategies and the criterion of hypotheses choice in order to increase plausibility: puzzling observation, abduction, retroduction, updating, deduction, induction, and recycle; and (2) the validity of our suggested multistage inference procedure for analyzing the “The Return of Halley’s Comet” case, which has been called Newtonianism’s most public triumph. Through an analysis of a case in the history of science, we describe the patterns of inference and the generation, through available data, of plausible hypotheses based on abductive inference. We then test these hypotheses with the deduction-induction cycle to determine which hypothesis is most plausible. A framework that includes the history of science can potentially provide a more consistent view of scientific practice and promote a deeper understanding of scientific concepts.

Strong photoluminescence at 1.53 μm from GaSb/AlGaSb multiple quantum wells grown on Si substrate

Strong photoluminescence at 1.53 μm was obtained from a GaSb/Al0.4Ga0.6Sb multiple-quantum-well sample grown on Si substrate, indicating greatly reduced defects by InSb quantum-dot layers that terminate dislocations. The carrier lifetime of 1.4 ns, comparable to typical InP-based quantum wells, and its independence on excitation power indicates the low defect density. Due to the wide well width and tensile strain, photoluminescence was dominated by the light hole-electron transition at low temperature. However, the heavy hole-electron transition was dominant at room temperature due to the proximity of energy levels and higher density of states for the heavy hole transition.

Suggesting a Flow Map of the Nature of Science for Sciences Education

The purpose of this study is to develop the flow map of history of science (HOS) instruction on students learning of nature of science (NOS) and science content knowledge (SCK) in order to enhance students’ overall scientific literacy. The NOS aspects have been emphasized in recent science education reform documents as disagreeing with the received views of common science. Thus, it is valuable to introduce students at the elementary level to some of the ideas developed by Kuhn. Key aspects of the nature of science (see Lederman et al. 2002) are in fact good applications to the history of science through Kuhn’s philosophy. Therefore, an NOS flow map could be a promising means of understanding the NOS tenets and an explicit and reflective tool for science teachers to enhance scientific teaching and learning. In the present study, I suggest that we should include instruction about HPS in our science teachers’ programs.

The Structure and Conceptual Changes of Preservice Secondary Teachers` Alternative Conceptions on Radioactive Isotopes

This study was aimed to understand the structures of preservice secondary school teachers` alternative conceptions on radioactive isotopes in the interior of earth. The structure of their conceptions were analyzed by the suggestions of Niaz (1988) based on the Lakatosian frameworks. The survey was carried out on a group of seventeen students who were major in science education. The research method was open-ended written questionnaire. The results of this study show that students had apparent alternative conceptions. The high temperature and pressure` explanation for radioactive decay in earth`s interior had most import effects on their alternative conceptions. It was also intended to survey their conceptional change by our teaching strategies of the philosophy of science in order to construct science concepts.

Using the Lakatosian Conflict Map for conceptual change of pre-service elementary teachers about the seasons

Abstract Background: Kuhn’s model of science has been widely influential, but in this paper, it is argued that it is more appropriate to consider constructivist learning within science education as a research program in the sense used by Lakatos. Purpose/Hypothesis: This study offers teaching strategies and their corresponding instructional sequences based on Lakatosian Methodology, and examines the effects of a Lakatosian Conflict Map using pre-service elementary teachers’ conceptual understandings of the causes of seasons. Design/Method: The Lakatosian Conflict Map was applied to concepts of seasonal change held by pre-service elementary teachers. Results: Most pre-service elementary teachers consistently protect their hard-core beliefs about seasonal change by offering auxiliary hypotheses related to earth’s elliptical orbit and the tilt of its rotational axis in response to activities designed to promote conceptual change around knowledge related to the cause of the seasons. Specifically, the critical event rather than the discrepant event in the Lakatosian Conflict Map was conducted in a Lakatosian conflict group and these students were allowed to explicitly express their representations about the phenomena derived from these events. The result of this study is that instruction using the new Lakatosian Conflict Map produced more favorable outcomes in terms of conceptual change than traditional instruction. Conclusions: This research concludes that the Lakatosian Conflict Map can help science teachers and students resolve the conflicts between students’ existing ideas and target scientific concepts.

Traditional East Asian Views and Traditional Western Views on the Heavens: The Discovery of Halley’s Comet

Traditional astronomy in East Asia developed very differently from that of the Western world, and it was informed by the views of nature inherent to East Asia. This research aims to examine how fundamental forces such as “yin-yang polarity,” a core concept of the East Asian view of nature, were reflected in the traditional astronomy of the region. In East Asia, astronomical works that carefully examined the celestial bodies were considered very important, and an astronomical system that was connected to the “human condition” was established. Analogical reasoning or correlative or “associative” thinking were dominant in the region. This connection with the human condition played an important role in the unique astronomy of East Asia, contrasting the mechanical worldview typical in Eastern Europe.

Microstructural characteristics of GaN/AlN thin films grown on a Si (110) substrate by molecular beam epitaxy: Transmission electron microscopy study

1 Korea Research Institute of Standards and Science, 267 Gajeong-Ro, Yuseong-Gu, Daejeon 34113, Republic of Korea 2 IV Works Co., Ansan, Kyungki-do 425-833, Republic of Korea 3 Department of Physics, Chungnam National University, 99 Daehak-Ro, Yuseong-Gu, Daejeon 34134, Republic of Korea 4 Division of Electrical and Computer Engineering, Hanyang University, Ansan city, Kyunggi-do 15588, Republic of Korea

Understanding Galileo’s Inquiries About the Law of Inertia

The purpose of this research is to gain a better understanding of the role of abstraction and idealization in Galileo’s scientific inquiries about the law of inertia, which occupies an important position in the history of science. We argue that although the terms “abstraction” and “idealization” are variously described in the recent literature, the concepts must be adopted to highlight important epistemological problems. In particular, we illustrate the importance of abstraction and idealization for the formation of the law of inertia by establishing a distinction between two types of entities: quasi-ideal entities and idealized entities. These theoretical laws should therefore be justified, using deduction and induction, through quasi-idealized entities based on data from the everyday world.