Drawing Activity Diagrams

Activity diagrams experience an increasing importance in the design and description of software systems. Unfortunately, previous approaches for automatic layout support fail or are just insufficient to capture the complexity of the related requirements. We propose a new approach tailored to the needs of activity diagrams which combines the advantages of two fundamental layout concepts called "Sugiyama's approach" and "topology-shape-metrics approach", originally developed for layered layouts of directed graphs and for orthogonal layout of undirected graphs respectively

OPTICAL AND SCANNING PROBE STUDIES OF ISOLATED POLY (3-HEXYLTHIOPHENE) NANOFIBERS

Plastic electronics have an essential role in the future technologies owing to their compelling characteristics such as light weight, biocompatibity, low cost fabrication, and tunable optoelectronic properties. However, the performance of polymer-based devices strongly depends on the efficiency of exciton formation and dynamics that are themselves strongly sensitive to polymer molecular packing and structural order. Therefore, the current challenge in achieving high efficiency is establishing a correlation between molecular packing and exciton coupling. P3HT nanofibers represent an attractive platform for studying optical and electronic properties of exciton coupling because their nominal (highly crystalline) internal chain packing structure is known. A combination of wavelength-, time-, and polarization- resolved photoluminescence imaging on isolated nanofibers made of P3HT with varying molecular weight (from 10 to 65 kDa) has revealed a transition in dominant exciton coupling from primarily interchain (H-aggregation) for low molecular weight nanofibers, to predominantly intrachain (J- aggregation) coupling for high molecular weight nanofibers. Based on nanofiber width measurements from TEM imaging, the driving force for this transition appears to be folding of individual polymer chains within the lamellae, resulting in enhanced chain planarity and reduced torsional disorder. In addition, it is shown that mechanically and chemically robust functionalized poly- (3-hexylthiophene) (P3HT) nanofibers can be made via chemical cross-linking. Dramatically different photophysical properties are observed depending on the choice of functionalizing moiety and cross-linking strategy. It is shown by a variety of photophysical metrics that by controlling the size of the cross-linking agent relative to alkyl side chain length, exciton coupling in P3HT nanofibers can be controlled, either by including a relatively large linker, which reduces inter- chain coupling, or alternatively using a linker of com- parable length to the lamellar spacing which minimally perturbs the aggregate structure. KPFM measurements have revealed an interesting dependence of surface potential contrast (SPC) with P3HT nanostructure morphology. These results indicate that changes in the structural order are positively correlated with HOMO level energies in structures with effective one-dimensional excitonic coupling (high molecular weight regime), and are negatively correlated in effectively two-dimensional structures (low molecular weight regime). Moreover, it is recognized that the cross-linked aggregates show optical and electronic properties that are analogous to solvated chains because of their perturbed interchain coupling. We believe the results presented in this thesis provide new insights into polymer morphology “design rules” for optimizing OPV device performance

Studies of a cyanine-based biosensor and light-induced antibacterial activities of oligo(phenylene ethynylene)s

This dissertation has been focusing on two subjects: biosensor development and light-activated antimicrobials. A cyanine-based fluorescent biosensor is developed with high sensitivity to detect the presence and activity of caspase-3/7. We demonstrated that supramolecular self-assembly can be useful for designing biosensors. A series of p-Phenylene Ethynylenes (OPEs) have been synthesized. Further photophysical studies show that these molecules have good singlet oxygen yields. The antimicrobial capability increases dramatically when exposed to UV-365 radiation, though dark biocidal activity can be obtained as well. This phenomenon is probably due to the high yields of singlet oxygen of these OPEs, which oxidizes unsaturated membrane and inner components of bacteria, such as protein, DNA, etc. viii Coupled with our previous work about the interactions of EO-OPE-1s with DOPC/cholesterol vesicles, we believe the biocidal process involves (1) EO-OPE-1s penetrate the bacterial membrane, (2) EO-OPE-1s photosensitize the generation of singlet oxygen and other reactive oxygen species and (3) singlet oxygen and/or reactive oxygen species trigger the cytotoxicity

Implantable photonic neural probes for light-sheet fluorescence brain imaging

Significance: Light-sheet fluorescence microscopy is a powerful technique for high-speed volumetric functional imaging. However, in typical light-sheet microscopes, the illumination and collection optics impose significant constraints upon the imaging of non-transparent brain tissues. Here, we demonstrate that these constraints can be surmounted using a new class of implantable photonic neural probes. Aim: Mass manufacturable, silicon-based light-sheet photonic neural probes can generate planar patterned illumination at arbitrary depths in brain tissues without any additional micro-optic components. Approach: We develop implantable photonic neural probes that generate light sheets in tissue. The probes were fabricated in a photonics foundry on 200 mm diameter silicon wafers. The light sheets were characterized in fluorescein and in free space. The probe-enabled imaging approach was tested in fixed and in vitro mouse brain tissues. Imaging tests were also performed using fluorescent beads suspended in agarose. Results: The probes had 5 to 10 addressable sheets and average sheet thicknesses < 16 μm for propagation distances up to 300 μm in free space. Imaging areas were as large as ≈ 240 μm x 490 μm in brain tissue. Image contrast was enhanced relative to epifluorescence microscopy. Conclusions: The neural probes can lead to new variants of light-sheet fluorescence microscopy for deep brain imaging and experiments in freely-moving animals

Implantable photonic neural probes for light-sheet fluorescence brain imaging

Significance: Light-sheet fluorescence microscopy (LSFM) is a powerful technique for highspeed volumetric functional imaging. However, in typical light-sheet microscopes, the illumination and collection optics impose significant constraints upon the imaging of non-transparent brain tissues. We demonstrate that these constraints can be surmounted using a new class of implantable photonic neural probes. Aim: Mass manufacturable, silicon-based light-sheet photonic neural probes can generate planar patterned illumination at arbitrary depths in brain tissues without any additional micro-optic components. Approach: We develop implantable photonic neural probes that generate light sheets in tissue. The probes were fabricated in a photonics foundry on 200-mm-diameter silicon wafers. The light sheets were characterized in fluorescein and in free space. The probe-enabled imaging approach was tested in fixed, in vitro, and in vivo mouse brain tissues. Imaging tests were also performed using fluorescent beads suspended in agarose. Results: The probes had 5 to 10 addressable sheets and average sheet thicknesses <16 μm for propagation distances up to 300 μm in free space. Imaging areas were as large as ≈240 μm × 490 μm in brain tissue. Image contrast was enhanced relative to epifluorescence microscopy. Conclusions: The neural probes can lead to new variants of LSFM for deep brain imaging and experiments in freely moving animals

Conference of Microelectronic Research 1997

https://scholarworks.rit.edu/meec_archive/1006/thumbnail.jp

Mechanics, mechanisms, and modeling of the chemical mechanical polishing process

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references.The ever-increasing demand for high-performance microelectronic devices has motivated the semiconductor industry to design and manufacture Ultra-Large-Scale Integrated (ULSI) circuits with smaller feature size, higher resolution, denser packing, and multi-layer interconnects. The ULSI technology places stringent demands on global planarity of the Interlevel Dielectric (ILD) layers. Compared with other planarization techniques, the Chemical Mechanical Polishing (CMP) process produces excellent local and global planarization at low cost. It is thus widely adopted for planarizing inter-level dielectric (silicon dioxide) layers. Moreover, CMP is a critical process for fabricating the Cu damascene patterns, low-k dielectrics, and shallow isolated trenches. The wide range of materials to be polished concurrently or sequentially, however, increases the complexity of CMP and necessitates an understanding of the process fundamentals for optimal process design. This thesis establishes a theoretical framework to relate the process parameters to the different wafer/pad contact modes to study the behavior of wafer-scale polishing. Several models of polishing - microcutting, brittle fracture, surface melting and burnishing - are reviewed. Blanket wafers coated with a wide range of materials are polished to verify the models. Plastic deformation is identified as the dominant mechanism of material removal in fine abrasive polishing.(cont.) Additionally, contact mechanics models, which relate the pressure distribution to the pattern geometry and pad elastic properties, explain the die-scale variation of material removal rate (MRR) on pattern geometry. The pad displacement into low features of submicron lines is less than 0.1 nm. Hence the applied load is only carried by the high features, and the pressure on high features increases with the area fraction of interconnects. Experiments study the effects of pattern geometry on the rates of pattern planarization, oxide overpolishing and Cu dishing. It was observed that Cu dishing of submicron features is less than 20 nm and contributes less to surface non-uniformity than does oxide overpolishing. Finally, a novel in situ detection technique, based on the change of the reflectance of the patterned surface at different polishing stages, is developed to detect the process endpoint and minimize overpolishing. Models that employ light scattering theory and statistical treatment correlate the sampled reflectance with the surface topography and Cu area fraction for detecting the process regime and endpoint. The experimental results agree well with the endpoint detection schemes predicted by the models.by Jiun-Yu Lai.Ph.D

Experimental and Molecular Dynamics Studies on Copper Electrochemical Mechanical Polishing (Cu-Ecmp)

In recent times, copper electrochemical mechanical polishing (Cu ECMP) has received a great deal of interest from electrochemists and the semiconductor manufacturing industry. This attention is primarily due to its potential for yielding relatively defect-free surfaces with improved surface integrity compared to chemical mechanical planarization (CMP). In this work, Cu ECMP apparatus integrated with a sensing and data acquisition system was developed to polish D. 4 inch (D.100 mm) blank Cu wafer surfaces to a finish of Ra< 15nm, and continuously gather voltage and current signals during Cu ECMP process at a sampling rate of 100Hz. Experimental studies were carried out to understand the effects of anodic voltage, pH, and pad pressure on the material removal rate (MRR) and surface roughness (Ra). Understanding the process from an atomistic standpoint helps us gain better control over the process and aids us in optimizing the key process output variables (KPOV). In order to gain a better understanding of the process, the molecular dynamic simulation (MDS) technique was adopted to develop a model to depict the real-time formation of copper (II) hexa-hydrate molecule Cu[(H_2 O)_6 ]^(2+), which is one of the key elements of the passivation layer formed over the Cu surface during ECMP. The behavior of the complex molecule under an electric force field was simulated to observe the process from a molecular perspective. From the trajectory of Cu2+, it was found that the velocity of copper ion increased with increase in applied voltage. Furthermore, the current carried by a single Cu2+ ion was computed based on the applied voltage and velocity of the ion.Industrial Engineering & Managemen

Micro/Nano Manufacturing

Micro- and nano-scale manufacturing has been the subject of ever more research and industrial focus over the past 10 years. Traditional lithography-based technology forms the basis of micro-electro-mechanical systems (MEMS) manufacturing, but also precision manufacturing technologies have been developed to cover micro-scale dimensions and accuracies. Furthermore, these fundamentally different technology platforms are currently combined in order to exploit the strengths of both platforms. One example is the use of lithography-based technologies to establish nanostructures that are subsequently transferred to 3D geometries via injection molding. Manufacturing processes at the micro-scale are the key-enabling technologies to bridge the gap between the nano- and the macro-worlds to increase the accuracy of micro/nano-precision production technologies, and to integrate different dimensional scales in mass-manufacturing processes. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on novel methodological developments in micro- and nano-scale manufacturing, i.e., on novel process chains including process optimization, quality assurance approaches and metrology