Monte Carlo Simulation of Electron Scattering in Resist Film/Substrate Targets

First the fundamentals of resist modelling required to implement an analysis of developed resist patterns were studied, which represents the relationship between the energy deposited by incident electrons and the solubility characteristics of a positive or negative resist. Next, two models of single elastic scattering and fast secondary (knock-on) electron production were studied for Monte Carlo simulation of electron scattering in resist film/substrate targets, and the statistical errors of Monte Carlo results were evaluated. Finally, problems in electron beam lithography were investigated with the simulation. The exposure intensity distribution was studied with the two models. A comparison between Monte Carlo calculations and experiments shows that a better agreement is obtained with the knock-on model. An analysis of developed negative resist patterns has been performed by using Monte Carlo results for energy dissipation. A comparison with experimental results revealed that developed resist patterns deform while being stuck to the Si surface by a strong adhesion. Also the time evolution of developed profiles of PMMA (polymethyl methacrylate) resist films was investigated based on the Monte Carlo results for energy dissipation. A quantitative comparison between theory and experiment suggests that some modification is necessary for the empirical constants in the solubility rate due to the electron beam irradiation effect. The spatial resolution was examined for an iso lated PMMA film. Resolutions of 320Å. and 530 Å were found with the single scattering and the knock-on models, respectively. The result with the knock-on model is similar to an experiment value of 600 Å obtained previously. It seems that the knock-on model may be useful for a theoretical study of the ultimate resolution in electron beam lithography

Data assimilation approach for addressing imperfections in people flow measurement techniques using particle filter

Understanding and predicting people flow in urban areas is useful for decision-making in urban planning and marketing strategies. Traditional methods for understanding people flow can be divided into measurement-based approaches and simulation-based approaches. Measurement-based approaches have the advantage of directly capturing actual people flow, but they face the challenge of data imperfection. On the other hand, simulations can obtain complete data on a computer, but they only consider some of the factors determining human behavior, leading to a divergence from actual people flow. Both measurement and simulation methods have unresolved issues, and combining the two can complementarily overcome them. This paper proposes a method that applies data assimilation, a fusion technique of measurement and simulation, to agent-based simulation. Data assimilation combines the advantages of both measurement and simulation, contributing to the creation of an environment that can reflect real people flow while acquiring richer data. The paper verifies the effectiveness of the proposed method in a virtual environment and demonstrates the potential of data assimilation to compensate for the three types of imperfection in people flow measurement techniques. These findings can serve as guidelines for supplementing sparse measurement data in physical environments

A Research on the Treatment of Complex Sulphide Ores. V : On the Recovery of Sulphur

Hydrogen sulphide was oxidized with air in the presence of iron, manganese or vanadium oxide as catalyst. The main product of the oxidation was either elementary sulphur or sulphur dioxide according to the ratio of air to hydrogen sulphide. When hydrogen sulphide was mixed to about 29% with air, a maximum yield of sulphur was obtained amounting to about 90% and sulphur dioxide which was formed simultaneously was a little. Amount of sulphur formed decreased and that of sulphur dioxide increased as the ratio of air to hydrogen sulphide was increased. With a mixture containing 12% of hydrogen sulphide, 80% of the sulphur was oxidized to sulphur dioxide and the remainder was found as elementary sulphur. The oxidation took place at relatively low temperature At 200～400℃, 90% of the sulphur was recoreved as elementary sulphur with a mixture which contained 28% of hydrogen sulphide. An effect of flowing rate on the reaction was little

The Spatial Distribution of Backscattered Electrons Revisited with a New Monte Carlo Simulation

A Monte Carlo simulation program including the discrete energy loss process has been developed, based on the Mott cross section for elastic scattering and the Vriens cross section for inelastic scattering. A deficiency of the previous model which is based on the screened Rutherford cross section and the Bethe law is made clear, from comparison between the new and old results such as the energy distribution of backscattered electrons for a Cu target. With the new Monte Carlo model, the radial spreading and penetration depth of both all and low-loss backscattered electrons have been studied for the Cu target at electron energies of 5.10 and 20 keV. From these studies, it is found that the electron exit angle dependence of the spatial spreading is more significant with the low-loss backscattered electrons and a very high resolution of 2 to 3 nm can be obtained even with backscattered electrons

Specificity of iron-phytosiderophore transporter

Hordeum vulgare L. yellow stripe 1 (HvYS1) is a selective transporter of Fe(III)-phytosiderophores in barley that is responsible for iron acquisition from the soil. In contrast, maize Zea mays, yellow stripe 1 (ZmYS1) possesses broad substrate specificity. In this study, a quantitative evaluation of the transport activities of HvYS1 and ZmYS1 chimera proteins revealed that the seventh extracellular membrane loop is essential for substrate specificity. The loop peptides of both transporters were prepared and analysed by circular dichroism and NMR. The spectra revealed a higher propensity for α-helical conformation of the HvYS1 loop peptide and a largely disordered structure for that of ZmYS1. These structural differences are potentially responsible for the substrate specificities of the transporters

Structural element responsible for the Fe(III)–phytosiderophore specific transport by HvYS1 transporter in barley

AbstractHordeum vulgare L. yellow stripe 1 (HvYS1) is a selective transporter for Fe(III)–phytosiderophores, involved in primary iron acquisition from soils in barley roots. In contrast, Zea mays yellow stripe 1 (ZmYS1) in maize possesses broad substrate specificity, despite a high homology with HvYS1. Here we revealed, by assessing the transport activity of a series of HvYS1–ZmYS1 chimeras, that the outer membrane loop between the sixth and seventh transmembrane regions is essential for substrate specificity. Circular dichroism spectra indicated that a synthetic peptide corresponding to the loop of HvYS1 forms an α-helix in solution, whereas that of ZmYS1 is flexible. We propose that the structural difference at this particular loop determines the substrate specificity of the HvYS1 transporter