Abstract In this study, ZrN films were deposited on silicon wafer¡Bcopper and aluminum sheets by reactive sputtering of Zr target at room temperature in a mixed N2-Ar atmosphere with N2 gas flow rates of 5 and 6 sccm. Films of ZrN about 1£gm thick were annealed at various temperatures in order to study the grain growth and the inter-diffusion of atoms. Electron probe X-ray microanalyzer¡]EPMA¡^ showed that the as-deposited ZrN films were stoichiometric. The ring patterns of electron diffraction in transmission electron microscope (TEM) indicated that only ZrN was present without any Zr metal. The grain size of ZrN showed no apparent change after annealing at 900¢J and 1000¢J, but showed that¡]200¡^ orientation is preferred to ¡]111¡^orientation. No Zr-Si compound were found at the ZrN/Si interface after annealing. It was revealed that the ZrN grain size in the ZrN/Si interface was about 5¡ã15 nm, then broadened to columnar structure of 20¡ã50nm in diameter away from the interface. The grain size of ZrN on Cu substrate was 3¡ã15 nm at the ZrN/Cu interface and leave away from the interface was 10¡ã80 nm. No Cu-Zr compound was found at the interface after annealing at 650¢J for 1 hour.

abstract: ABSTRACT Group III-nitride semiconductor materials have been commercially used in fabrication of light-emitting diodes (LEDs) and laser diodes (LDs) covering the spectral range from UV to visible and infrared, and exhibit unique properties suitable for modern optoelectronic applications. Great advances have recently happened in the research and development in high-power and high-efficiency blue-green-white LEDs, blue LDs and other optoelectronic applications. However, there are still many unsolved challenges with these materials. In this dissertation, several issues concerning structural, electronic and optical properties of III-nitrides have been investigated using a combination of transmission electron microscopy (TEM), electron holography (EH) and cathodoluminescence (CL) techniques. First, a trend of indium chemical inhomogeneity has been found as the indium composition increases for the InGaN epitaxial layers grown by hydride vapor phase epitaxy. Second, different mechanisms contributing to the strain relaxation have been studied for non-polar InGaN epitaxial layers grown on zinc oxide (ZnO) substrate. Third, various structural morphologies of non-polar InGaN epitaxial layers grown on free-standing GaN substrate have been investigated. Fourth, the effect of the growth temperature on the performance of GaN lattice-matched InAlN electron blocking layers has been studied. Finally, the electronic and optical properties of GaN nanowires containing a AlN/GaN superlattice structure have been investigated showing relatively small internal electric field and superlattice- and defect-related emissions along the nanowires. / Dissertation/Thesis / Ph.D. Physics 2011

This thesis quantitatively investigates gaseous electron-ion recombination in an environmental scanning electron microscope (ESEM) at a transient level by utilizing the dark shadows/streaks seen in gaseous secondary electron detector (GSED) images immediately after a region of enhanced secondary electron (SE) emission is encountered by a scanning electron beam. The investigation firstly derives a theoretical model of gaseous electron-ion recombination that takes into consideration transients caused by the time constant of the GSED electronics and external circuitry used to generate images. Experimental data of pixel intensity versus time of the streaks is then simulated using the model enabling the relative magnitudes of (i) ionization and recombination rates, (ii) recombination coefficients, and (iii) electron drift velocities, as well as absolute values of the total time constant of the detection system, to be determined as a function of microscope operating parameters. Results reveal the exact dependence that the effects of SE-ion recombination on signal formation have on reduced electric field intensity and time in ESEM. Furthermore, the model implicitly demonstrates that signal loss as a consequence of field retardation due to ion space charges, although obviously present, is not the foremost phenomenon causing streaking in images, as previously thought. Following that the generation and detection of gaseous scintillation and electro- luminescence produced via electron-gas molecule excitation reactions in ESEM is investigated. Here a novel gaseous scintillation detection (GSD) system is developed to efficiently detect photons produced. Images acquired using GSD are compared to those obtained using conventional GSED detection, and demonstrate that images rich in SE contrast can be achieved using such systems. A theoretical model is developed that describes the generation of photon signals by cascading SEs, high energy backscattered electrons (BSEs) and primary beam electrons (PEs). Photon amplification, or the total number of photons produced per sample emissive electron, is then investigated, and compared to conventional electronic amplification, over a wide range of microscope operating parameters, imaging gases and photon collection geometries. The main findings of the investigation revealed that detected electroluminescent signals exhibit larger SE signal-to-background levels than that of conventional electronic signals detected via GSED. Also, dragging the electron cascade towards the light pipe assemblage of GSD systems, or electrostatic focusing, dramatically increases photon collection efficiencies. The attainment of such an improvement being a direct consequence of increasing the `effective' solid angle for photon collection. Finally, in attempt to characterize the scintillating wavelengths arising from sample emissive SEs, PEs, BSEs, and their respective cascaded electrons, such that future photon filtering techniques can be employed to extract nominated GSD imaging signals, the emission spectra of commonly utilized electroluminescent gases in ESEM, such as argon (Ar) and nitrogen (N2), were collected and investigated. Spectra of Ar and N2 reveal several major emission lines that occur in the ultraviolet (UV) to near infrared (NIR) regions of the electromagnetic spectrum. The major photon emissions discovered in Ar are attributed to occur via atomic de-excitation transitions of neutral Ar (Ar I), whilst for N2, major emissions are attributed to be a consequence of second positive band vibrational de-excitation reactions. Major wavelength intensity versus gas pressure data, for both Ar and N2, illustrate that wavelength intensities increase with decreasing pressure. This phenomenon strongly suggesting that quenching effects and reductions in excitation mean free paths increase with imaging gas pressure.

This master’s project report deals with the process development for patterning thesub-micron features using Deep-UV photolithography. Patterning of the sub-micronstructures in the resists UV26 and ZEP520A-7 has been demonstrated successfully. Using theKarl Süss-MJB4 DUV mask aligner, trenches of width down to 535 nm have been obtained.Good results have been obtained in these experiments considering the development time andthe exposure time, which are found to be shorter compared to previously published results.This provides a faster process and higher throughput. Experimental steps along with thefurther improvement areas are discussed.Equipment used include a Karl Süss-MJB4 DUV mask aligner, an optical microscope anda Scanning Electron Microscope (SEM).

This thesis quantitatively investigates gaseous electron-ion recombination in an environmental scanning electron microscope (ESEM) at a transient level by utilizing the dark shadows/streaks seen in gaseous secondary electron detector (GSED) images immediately after a region of enhanced secondary electron (SE) emission is encountered by a scanning electron beam. The investigation firstly derives a theoretical model of gaseous electron-ion recombination that takes into consideration transients caused by the time constant of the GSED electronics and external circuitry used to generate images. Experimental data of pixel intensity versus time of the streaks is then simulated using the model enabling the relative magnitudes of (i) ionization and recombination rates, (ii) recombination coefficients, and (iii) electron drift velocities, as well as absolute values of the total time constant of the detection system, to be determined as a function of microscope operating parameters. Results reveal the exact dependence that the effects of SE-ion recombination on signal formation have on reduced electric field intensity and time in ESEM. Furthermore, the model implicitly demonstrates that signal loss as a consequence of field retardation due to ion space charges, although obviously present, is not the foremost phenomenon causing streaking in images, as previously thought. Following that the generation and detection of gaseous scintillation and electro- luminescence produced via electron-gas molecule excitation reactions in ESEM is investigated. Here a novel gaseous scintillation detection (GSD) system is developed to efficiently detect photons produced. Images acquired using GSD are compared to those obtained using conventional GSED detection, and demonstrate that images rich in SE contrast can be achieved using such systems. A theoretical model is developed that describes the generation of photon signals by cascading SEs, high energy backscattered electrons (BSEs) and primary beam electrons (PEs). Photon amplification, or the total number of photons produced per sample emissive electron, is then investigated, and compared to conventional electronic amplification, over a wide range of microscope operating parameters, imaging gases and photon collection geometries. The main findings of the investigation revealed that detected electroluminescent signals exhibit larger SE signal-to-background levels than that of conventional electronic signals detected via GSED. Also, dragging the electron cascade towards the light pipe assemblage of GSD systems, or electrostatic focusing, dramatically increases photon collection efficiencies. The attainment of such an improvement being a direct consequence of increasing the `effective' solid angle for photon collection. Finally, in attempt to characterize the scintillating wavelengths arising from sample emissive SEs, PEs, BSEs, and their respective cascaded electrons, such that future photon filtering techniques can be employed to extract nominated GSD imaging signals, the emission spectra of commonly utilized electroluminescent gases in ESEM, such as argon (Ar) and nitrogen (N2), were collected and investigated. Spectra of Ar and N2 reveal several major emission lines that occur in the ultraviolet (UV) to near infrared (NIR) regions of the electromagnetic spectrum. The major photon emissions discovered in Ar are attributed to occur via atomic de-excitation transitions of neutral Ar (Ar I), whilst for N2, major emissions are attributed to be a consequence of second positive band vibrational de-excitation reactions. Major wavelength intensity versus gas pressure data, for both Ar and N2, illustrate that wavelength intensities increase with decreasing pressure. This phenomenon strongly suggesting that quenching effects and reductions in excitation mean free paths increase with imaging gas pressure.

The purpose of this study was to evaluate the effect of a final rinse of ethanol on depth of sealer penetration in teeth obturated with Gutta Percha (GP)/AH-Plus® (Dentsply, De Trey GmbH, Konstanz, Germany) or Resilon/Epiphany® SE™ (Pentron Clinical Technologies, LLC, Wallingford, CT). Extracted human anterior teeth (n= 32) were shaped to size 30, 0.06 taper using nickel-titanium rotary files and subjected to an identical irrigation protocol. Specimens were randomly divided into eight groups according to final irrigating solution (saline, 70%, 95%, or 100% ethanol) and obturation material (GP/AH-Plus® or Resilon/EpiphanyÒ SE™). A 2mm thick slice was obtained by sectioning each obturated root at 3mm and 5mm from the anatomic apex. Specimens were cleared and assessed using scanning electron microscopy (SEM). Sealer penetration was observed at different magnifications when using GP/AH Plus® across all final rinse concentrations. Among Resilon/Epiphany® SE™ groups, no sealer penetration was evident under SEM. Conclusions: 1) GP/AH-Plus® showed evidence of sealer penetration, however, Resilon/Epiphany® SE™ did not show evidence of sealer penetration at both the dentin and sealer interface. 2) A final rinse with any concentration of ethanol prior to obturation does not improve sealer penetration with GP/AH-Plus® groups. 3). Resilon/Epiphany® SE™ bond can be dislodged at either the interface of sealer and Resilon or dentin and Resilon.

Spore morphology of Polypodiaceae and Grammitidaceae from Taiwan were studied with light microscope and scanning electron microscope. Totally 18 genera and 62 species were observed. Polypodiaceae spores are ellipsoidal and monolete except Loxogramme grammitoides; with spore ornamentation tuberculate, verrucate, echinate, globule, rugate, undulate, foveolate and/or vermiculate. Grammitidaceae spores are global, trilete with spore ornamentation granulate, tuberculate and/or globules. The spore surface ornamentation can be used as taxonomic characters in Polypodiaceae and Grammitidaceae at familial, genera and species levels. Based on spore characters, Polypodiaceae and Grammitidaceae can be differentiated, Loxogrammeae and Drynariaeae are not separable from the rest of Polypodiaceae, and the current classification system of Lepisorieae and Microsoreae are not .internal consistent.

This thesis deals with freezy sublimation in cryoattachement Gatan Alto 2500 connected to scanning electron microscope (SEM) JEOL JSM-7401F. The thesis is devided into the theoretical and practical parts. In the theoretical part I focus mainly on physical qualities of water and on problematics of freezy-drying. I also describe qualities of subsidiary substances which are being used when working with cryotechnology. I briefly describe technology used: cryoattachement Alto 2500 and SEM JSM-7401F. In the practical part I deal with the description of the method that I have developed in order to measure weight decrease of frozen specimen owning to its sublimation in vacuum. I provide measurement results of the sublimation of these substances: demineralized water, Dextran, glycerol and phosphate buffer saline.

Abstract Increased amounts of epicuticular waxes and UV-absorbing compounds, such as flavonoids, and smaller leaf/needle surface area are plant defence mechanisms against UV-B radiation. The response of the needle epicuticular waxes of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies Karst.) seedlings to increased UV-B were investigated in short-term and long-term greenhouse experiments. In a more realistic long-term field experiment with mature Scots pines, the methanol-extractable UV-absorbing compounds were also analysed. Some significant changes were observed in the wax tube distribution (WTD, %) and the amount of waxes in Norway spruce seedlings in the short-term Belgian greenhouse experiment (UV-BBE 0, 11.3 and 22.6 kJ m-2 d-1), but no changes were detected in Scots pine seedlings. No changes in waxes were observed in the long-term Finnish greenhouse experiment (UV-BBE 0, 2.2–6.6 and 5.6–16.8 kJ m-2 d-1), where both the Norway spruce and the Scots pine seedlings seemed to respond by having smaller needle surface areas. A field experiment (UV-BBE 0.5–2.4 kJ m-2 d-1 and 0.7–5.1 kJ m-2 d-1) with mature Scots pines revealed no significant changes in WTD during the three growing seasons or the amount of waxes during the third growing season. In the long-term field experiment the amount of UV-absorbing compounds varied significantly between seasons and/or needle age classes. Elevated amounts of these compounds were already observed in the three-day-old needles and also in the oldest (c + 2) needles when the waxes were still undeveloped or already somewhateroded. No significant differences in the amount of UV-absorbing compounds were observed between the treatments during the first and second growing seasons. During the third growing season, needles of all ages contained significantly or slightly less UV-absorbing compounds in supplemental UV-B than in the ambient treatment, possibly due to cumulative effects of UV-B in already inhibited pigment synthesis. This suggests that these defence mechanisms are not efficient enough to prevent the UV-B-induced damage in the long term.

This thesis is involved in image processing of medical data and its implementation using Java programming language. The main contribution of this thesis is creation of algorithms for feature extraction from 3D data and subsequent verification of the results for the issue of imagining 3D brain data, and creation of image filters and their implementation in the program RapidMiner. Consequently, the segmentation process is created at the 2D and 3D level, and output of 3D level segmentation are segmented brain structures. Furthermore, segmentation algorithms were compared on the basis of the final form of segmented structures and this approach was compared with other works.