Formation and Properties of Metallic Nanoparticles on Compound Semiconductor Surfaces.

When electromagnetic radiation is incident upon metallic nanoparticles (NPs), a collective oscillation, termed a surface plasmon resonance (SPR), is generated. Recently, metallic NPs on semiconductor surfaces have enabled the generation of SPR, promising for enhanced light emission, efficient solar energy harvesting, biosensing, and metamaterials. Metallic NPs have been fabricated by focused ion beam (FIB) which has an advantage of cost-effectiveness over conventional lithography process requiring multi-step processes. Here, we report formation and properties of FIB-induced metallic NPs on compound semiconductor surfaces. Results presented in this thesis study suggest that FIB-induced Ga NPs can be a promising alternative plasmonic material. In particular, using a combined experimental-computational approach, we discovered a universal mechanism for ion-induced NP formation, which is governed by the sputtering yield of semiconductor surfaces. We also discovered a governing mechanism for ion-induced NP motion, which is driven by thermal fluctuation and anisotropic mass transport. Furthermore, we demonstrated Ga NP arrays with plasmon resonances with performance comparable to those of traditionally-used silver and gold NPs. We then finally demonstrated the Ga NP plasmon-induced enhancement of light emission from GaAs, which is the first ever combination of a new plasmonic material (Ga) and a new fabrication method (FIB) for the plasmon-enhanced light emission.PhDMaterials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/107301/1/myungkoo_1.pd

Impact of raw material surface oxide removal on dual band infrared optical properties of As2Se3 chalcogenide glass

The manufacturing of low loss chalcogenide glasses (ChGs) for optoelectronic applications is ultimately defined by the concentration of impurities present in starting materials or imparted via processing. We describe a rapid method for purifying metallic starting materials in As2Se3 glass where oxide reduction is correlated to optical and physical properties. Specifically, As-O reduction enhances the glass' dual-band optical transparency proportional to the extent (13-fold reduction) of oxide reduction, and is accompanied by a change in density and hardness associated with changes in matrix bonding. A significant modification of the glass' index and LWIR Abbe number is reported highlighting the significant impact purification has on material dispersion control required in optical designs. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Melt Property Variation In GeSe2-As2Se3-PbSe Glass Ceramics For Infrared Gradient Refractive Index (GRIN) Applications

Melt size-dependent physical property variation is examined in a multicomponent GeSe2-As2Se3-PbSe chalcogenide glass developed for gradient refractive index applications. The impact of melting conditions on small (40 g) prototype laboratory-scale melts extended to commercially relevant melt sizes (1.325 kg) have been studied and the role of thermal history variation on physical and optical property evolution in parent glass, the glass\u27 crystallization behavior and post heat-treated glass ceramics, is quantified. As-melted glass morphology, optical homogeneity and heat treatment-induced microstructure following a fixed, two-step nucleation and growth protocol exhibit marked variation with melt size. These attributes are shown to impact crystallization behavior (growth rates, resulting crystalline phase formation) and induced effective refractive index change, neff, in the resulting optical nanocomposite. The magnitude of these changes is discussed based on thermal history related melt conditions

知識生産の独自的基盤と大学の改革 : ソウル大学を中心に

The purpose of this study was two-fold: first, the study critically reflected the current qualifications of humanities and social sciences researches in Seoul National University (SNU). Secondly, the study examined the institutional structure of research centers inside SNU, comparing American and European models of institutional arrangement. Based upon the above analyses the study attempted to propose strategic measures to improve quality of research in the humanities and social sciences. The study found that SNU’s research policy and faculty evaluation have heavily focused upon individual performance among faculties and researchers. Moreover, all of professors belong to the departments and only loosely affiliated to research institutes and centers. There are few professors who are willing to do research collaborations crossing departments and colleges. Such kind of institutional arrangement hardly produces long term researches which could be done by a group of common research interests. In contrast to the individually based model of research promotion which most American universities are following, the European model tends to emphasize more concentrated research topic or themes to preserve the research quality. Many European and Japanese research institutes inside or outside universities do have their own tenured professors and researchers, concentrating small numbers of research clusters or themes. Such an “independent model” is effective when research funding and human resources are limited. Taking into account different models of research institutes, the study proposed an integrated model of institutional arrangements. And it also suggested that performance evaluations of professors and researchers need to emphasize group collaborations and institutional researches