Micron-scale characterization of laser processed silicon via low temperature micro-photoluminescence spectroscopy

Laser processing is now regarded as a promising tool to reduce the cost and complexity of fabricating the formation of localized contacts between heavily doped silicon and metal, features which have become an important element in high efficiency silicon solar cells, such as a passivated emitter and rear cell (PERC) and an interdigitated back contact cell (IBC). However, characterization of localized features with conventional PV characterization tools is challenging, mainly due to the limitations of spatial resolution. This thesis develops and applies novel characterization methods to these localized features using low temperature micro-photoluminescence spectroscopy (μ-PLS). This technique demonstrates that localized features, even single laser pulse processed regions typically tens of micrometres in scale, can be investigated directly without the need for specific sample structures and their electronic properties can be mapped spatially in the sub-micrometre regime. Utilizing the sub-micron precision of these measurements, the laser-induced crystallographic damages were investigated at various positions within the laser-processed region, particularly at specific points such as the boundary/edge of processed and unprocessed regions. It was found that the edge, or pulse overlapped regions, were significantly more defective than the centre region. The impact of laser parameters, such as laser pulse fluence and number of repeat pulses, on laser-induced damage was also analysed. Significantly different levels of defect-related PL signals were observed after laser processing of the two different substrate surface conditions. This suggests that wafer surface preparation can be an important factor impacting on the quality of laser-processed silicon. The doping profiles of thermally boron-diffused silicon samples, which have Gaussian function type doping profiles, can be estimated from the measured PL spectra alone. The wavelength of the doping-related PL peak (doping peak) has a reliable and simple linear relationship with the surface dopant density on a semi-log plot. The PL intensity of the doping peak also shows a linear relationship with the doping depth metric (depth factor), but only after considering the reduction of PL intensity due to enhanced incomplete dopant ionization at low temperature. Doping profiles can be easily reconstructed based on these two linear relationships and their vi accuracy was verified by comparisons with existing doping profiles (via ECV profiling). Mapping of the surface dopant density and the depth factor of micron-scale locally diffused features was undertaken using 2-D mapping with μ-PLS measurements at 2 μm spatial resolution. This method was also applied to 532 nm laser-doped silicon to show its effectiveness on locally laser-doped features. The doping profiles of laser-doped silicon were also successfully estimated from PL spectra measurements alone, along with 2-D maps of the surface dopant density and the depth factor of the laser-doped silicon. In addition, the impact of temporal pulse parameters, such as pulse duration and temporal pulse shapes, on the doping profiles and recombination properties of laser-doped silicon were investigated. By correlating defect-related PL band counts with the quantified recombination parameters determined by the luminescence-coupled numerical device simulations, it was shown that μ-PLS measurements are able to perform quantitative measurements of recombination properties. The last chapter of this thesis demonstrates an application of an advanced laser doping process using a stack of intrinsic amorphous silicon (Si:H(i)) and boron-doped amorphous silicon (a-Si:B). The results showed that this stack is able to provide excellent surface passivation as well as a sufficient amount of dopant source for laser doping. The method presented in this thesis is a very effective, simple and rapid characterization for analysing localized features, in particular spatially inhomogeneous laser-processed features on the micron-scale. This method enables the observation of the variation in properties within localized features which is not possible using conventional methods. It allows for a more in-depth study of laser processing and promotes further development of laser technologies for high efficiency cell fabrication

Extraskeletal chondroma of the fallopian tube.

Extraskeletal chondroma can occur in the hands, feet, head and neck. This tumor usually presents as a small solitary nodule. The histogenesis of the tumor is controversial, but some have suggested a metaplastic origin. Chondroma of the fallopian tube is very rare. There is only one report in English literature. The origin of this tumor can be subcoelomic mesenchyme of the tubal serosa or mesenchyme of the myosalpinx. We describe a case of chondroma arising from the serosal surface of the fallopian tube with a review of literature. A 30-yr-old woman visited hospital due to left adnexal mass. On operating finding, 2 x 3 cm sized nodular mass was noted on the left tubal serosal area. The excised mass showed multilobulated appearance covered with thin fibrous membrane. The cut surface was solid, grayish yellow, and myxoid with a focal gelatinous area. The microscopic finding showed islands and elongated lobules of mature benign cartilage without cytologic atypia

The Dual Process of Korean Labor Market Transformation: Decomposing the Size-Wage Gap, 1982~2004

Translated from an article published in the Korean Journal of Sociology 42(7): 111- 145, 2008 with permission from The Korean Sociological Association.This study aims to understand the nature of the structural change in the Korean labor market by analyzing the wage gap between large firms and small to medium-sized firms between 1982 and 2004. The result reveals that Korea experienced two historical moments in which the size-wage gap surged: one in 1987, the year of mass labor strikes spurred by the democratization movement, and the other in 1997, the year the Asian financial crisis began. Whereas the first moment was a temporary phenomenon lasting only until the early 1990s, the second moment led to a continuous wage-gap increase. The result of an Oaxaca-Blinder decomposition of the wage gap shows that the factors contributing to the widening of the wage gap since the economic crisis were different between the manual sector and the nonmanual sector. For manual workers, the increase of the size-wage gap was mostly induced by compositional effects, specifically the increased share of long-tenured workers in large firms. For non-manual workers, however, it was a price effect. In light of the current debate on the transformation of the internal labor market, we conclude that a corporate internal labor market exists persistently, although reduced in size, in the manual sector, whereas the corporate boundary is significantly weakened in the non-manual sector. This dual process of labor market transformation, however, results in an increased size-wage gap in both sectors, although for differing reasons

Guards and Culprits in the Endoplasmic Reticulum: Glucolipotoxicity and β-Cell Failure in Type II Diabetes

The endoplasmic reticulum (ER) is a cellular organelle responsible for multiple important cellular functions including the biosynthesis and folding of newly synthesized proteins destined for secretion, such as insulin. The ER participates in all branches of metabolism, linking nutrient sensing to cellular signaling. Many pathological and physiological factors perturb ER function and induce ER stress. ER stress triggers an adaptive signaling cascade, called the unfolded protein response (UPR), to relieve the stress. The failure of the UPR to resolve ER stress leads to pathological conditions such as β-cell dysfunction and death, and type II diabetes. However, much less is known about the fine details of the control and regulation of the ER response to hyperglycemia (glucotoxicity), hyperlipidemia (lipotoxicity), and the combination of both (glucolipotoxicity). This paper considers recent insights into how the response is regulated, which may provide clues into the mechanism of ER stress-mediated β-cell dysfunction and death during the progression of glucolipotoxicity-induced type II diabetes

Scutellinia (Pezizales) In Korea, With A New Species and Eight New Records

Eleven species of the genus Scutellinia (Pyronemataceae, Pezizales) are recognized in Korea by analysis of macro- and micro-morphological characteristics, substrates and geographical distributions. Eight species are recorded new to Korea, namely, S. ahmadiopsis, S. badio-berbis, S. colensoi, S. jilinensis, S. nigrohirtula, S. olivascens, S. setosa and S. patagonica. Based on the exceptional length of marginal hairs and tuberculate ascospore wall ornamentation, two Korean specimens occurring on wood are described as a new species. Infraspecific morphological variations among collections within S. scutellata and S. patagonica were found. These are tentative treat as species complexes. The highly questionable occurrence of S. setosa in Asia was confirmed. Descriptions and taxonomic notes of the recognized species of Scutellinia are provided with a taxonomic key, illustrations and photographs of these species from Korea.Organismic and Evolutionary Biolog

Clinical Characteristics and Risk Factors for Nosocomial Candidemia in Medical Intensive Care Units: Experience in a Single Hospital in Korea for 6.6 Years

The aim of this study was to determine candidemia incidence among patients in a medical intensive-care unit (MICU) and the associated mortality rate and to identify risk factors associated with candidemia. We retrospectively performed a 1:3 matched case-control study of MICU patients with candidemia. Controls were matched for sex, age, and Acute Physiology and Chronic Health Evaluation (APACHE) II score. Candidemia incidence was 9.1 per 1,000 admissions. The most common pathogen was Candida albicans. Crude mortality was 96% among candidemia patients and 52% among controls (P<0.001). Mortality differed significantly between the groups according to Kaplan-Meier survival analysis (P=0.024). Multivariate analysis identified the following independent risk factors for candidemia: central venous catheterization (odds ratio [OR] = 3.2, 95% confidence interval [CI]=1.2-9.0), previous steroid therapy (OR=4.7, 95% CI=1.8-12.1), blood transfusion during the same admission period (OR=6.3, 95% CI=2.4-16.7), and hepatic failure upon MICU admission (OR=6.9, 95% CI=1.7-28.4). In conclusion, we identify an additional independent risk factor for candidemia, the presence of hepatic failure on MICU admission. Therefore, increased awareness of risk factors, including hepatic failure, is necessary for the management of candidemia