The theoretical basis for using electron mirrors as correctors of chromatic aberration is presented and an experimental verification of correction of chromatic aberration is demonstrated. A hyperbolic electrostatic electron mirror operating in its converging range and at unity magnification was used as a corrector. A novel separating system with deflections taking place at image planes was developed to implement the mirror without impairing the resolution. Correction was demonstrated in an electron optical probe system. The chromatic aberration was measured by means of the shadows cast by a fine mesh placed near the final image. The experimental method and equipment are described. The experiment serves as a verification of the theory as well as a successful test of the method of separating the electron beams traveling to and from the mirror.

Optical signal processing is introduced as a tool for investigations in the field of television compression research. An optical signal processing system is designed, which performs the Fourier transform of a picture signal F[B(x,y)] and its reconstruction F⁻¹ {F [B(x,y)]} . Some basic optical filtering experiments are performed in the spatial frequency plane, and the optical analogue of the frequency sampling theorem is demonstrated. The Fourier transforms of test pattern pictures show large gaps which can be used for compression. Observation of complex spectra of continuous tone pictures is found to be impaired by noise effects. A physiological experiment is carried out, which investigates the relationship between tolerable flicker frequency and spatial frequency of a television picture. It is found that the tolerable flicker rate f decreases as the spatial frequency fx is increased, according to the empirical equation fc = fo exp(-kfx). fo and k are parameters depending on factors like contrast ratio, kind and size of picture, etc. Compression systems using the above results are found to have a limit of obtainable compression ratio of approximately 3 to 1. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

The energy distribution in an electron beam transmitted by a thin aluminum film was studied by a retarding potential method in which the energy analysis could be made as a function of the polar angle and azimuth of scattering. The results indicated that the transmitted beam contained electrons which had lost essentially zero energy and groups of electrons which had suffered losses of approximately15 ev and 25 ev and possib1y 75 ev. In addition there appeared to be a continuous background of energy losses over the range studied (from 0 to 80 ev). The resolution of the energy analyser was limited by the separation of the data points and was not adequate to observe the dependence of the 15 ev energy loss (plasma loss) on the polar angle of scattering. This study demonstrated the feasibility of this method of energy analysis as well as the short-comings of the apparatus. Suggestions for future improvements are made.

Photoemission electron microscopy (PEEM) uses photoelectrons excited from material surfaces by incident photons to probe the interaction of light with surfaces with nanometer-scale resolution. The point resolution of PEEM images is strongly limited by spherical and chromatic aberration. Image aberrations primarily originate from the acceleration of photoelectrons and imaging with the objective lens and vary strongly in magnitude with specimen emission characteristics. Spherical and chromatic aberration can be corrected with an electrostatic mirror, and here I develop a triode mirror with hyperbolic geometry that has two adjacent, field-adjustable regions. I present analytic and numerical models of the mirror and show that the optical properties agree to within a few percent. When this mirror is coupled with an electron lens, it can provide a large dynamic range of correction and the coefficients of spherical and chromatic aberration can be varied independently. I report on efforts to realize a triode mirror corrector, including design, characterization, and alignment in our microscope at Portland State University (PSU). PEEM may be used to investigate optically active nanostructures, and we show that photoelectron emission yields can be identified with diffraction, surface plasmons, and dielectric waveguiding. Furthermore, we find that photoelectron micrographs of nanostructured metal and dielectric structures correlate with electromagnetic field calculations. We conclude that photoemission is highly spatially sensitive to the electromagnetic field intensity, allowing the direct visualization of the interaction of light with material surfaces at nanometer scales and over a wide range of incident light frequencies.

A survey of the optical and electron paramagnetic resonance (E.F.R.) absorption in a large number of diamonds from all major sources of production has revealed that perfect diamond is virtually non-existent. One or more of eleven different types of defect centres is found in each specimen. The presence or absence of nitrogen has long been known to give rise to the distinctive properties of Type I and Type II diamond.The present survey has shown that the form in which the nitrogen is present is significant. In most specimens the nitrogen is present in substitutional, non-paramagnetic platelet form, and these specimens were classified as Type Ia diamonds. A small group of transparent natural diamonds was found to contain dispersed paramagnetic nitrogen. The optical properties of these diamonds are unlike those of other diamond types and have hitherto not been reported. It is proposed that these diamonds be classified as Type lb.Three new systems of E.P.R. lines were found in Type Ib diamond. They are shown to be due to: (i) 13C atoms situated in different positions relative to the substitutional nitrogen, (ii) interaction of the small quadrupole moment of the nitrogen with the electric field gradient, and (iii) the presence of the l5N isotope. Synthetic diamonds are found to be exclusively of the Type Ib variety, whereas natural Type Ib diamond are rare exceptions. This is attributed to the growth history of the specimens. In order to investigate the defect centres associated with nitrogen in diamond, Type Ia and Ib diamond were irradiated with 0.78 MeV electrons. The effects observed were complicated and therefore led to a general investigation of irradiation damage, and the annealing of irradiation damage in diamond. In addition to the G.R.l and U.V. bands induced in all diamond by irradiation damage, another optical absorption feature, the N.D.l band, is found in all Type Ia diamond after irradiation and limited heating. It is suggested that the N.D.l centre arises from the combination of a carbon interstitial, and nitrogen in platelet form, and that the other primary product of irradiation damage, a vacancy, is responsible for both the G.R.l and U.V. bands. The N.D.l centre acts as an acceptor, the G.R.l centre as a donor. In the ionized state G.R.l is inactive in optical absorption; N.D.l is active. Electron transfer by thermal excitation results in the bleaching of G.R.l and the enhancement of N.J.l. Illumination with light in the N.D.l band causes electron transfer in the reverse direction, restoring band strengths to their former condition. A model is proposed which defines the energies within the forbidden gap of the ground and excited states of G.R.l and N.D.l. On heat treatment at temperatures of 500°C and above, the G.R.l band in all diamonds anneals out. The rate of annealing, however, is founa to be dependent on the nitrogen concentration. Thus in Type IIa diamond (which contains no nitrogen) G.R.l anneals very slowly, resulting in the formation of an absorption tail. In Type Ia diamond G.R.l anneals much faster (the actual rate depending on the nitrogen concentration), and two optical absorption bands, 5032A and H2, are formed. It is proposed that the vacancy in diamond becomes mobile at about 500° C, and that the G.R.l band in Type IIa diamond anneals because of the agglomeration of vacancies, which results in the formation of defects responsible for the absorption tail. In Type Ia diamond the nitrogen platelets are ideal sinks for vacancies, because the lattice on either side of a platelet is in compression. G.R.l therefore anneals more rapidly and 5032A centres are formed due to the combination of a vacancy and a nitrogen platelet. The nature of the H2 centre is much more obscure, but a possible explanation is that H2 centres are formed in addition, because the N.D.l centres (nitrogen platelets with embedded interstitials) also succeed in trapping vacancies. Vacancy/interstitial recombinations are prevented since these defects are pinned to different locations in the platelet region. In type Ib diamonds N. D.l centres were found to form at a lower temperature than in Type Ia diamond. It is suggested that the carbon interstitial in diamond is mobile, and combines with Substitutional nitrogen in isolated positions at temperatures below 250°C. In Type Ia specimens, where the nitrogen is segregated in platelets, this process only occurs at about 250°C, when the interstitial has enough kinetic energy to overcome the energy barrier preventing it from combining with nitrogen inside the platelet region where it will relieve strain. Because of the different substitutional nitrogen configuration, the energy levels of N.D.l centres in Type Ib diamond are such that electron transfer by thermal excitation from G.R.l to N.D.l occurs at room temperature. Most of the G.R.l centres are therefore permanently ionized and optically inactive. After heat treatment, a new band called the 6400A band is formed in irradiated Type Ib diamond. It is suggested that 6400A centres are formed by the combination of mobile vacancies with substitutional nitrogen in isolated positions. The 6400A band is therefore analogous to the 5032A band produced in Type Ia diamond. As expected no analogue of the H2 is formed in Type Ib diamond, as both an interstitial and a vacancy cannot co-exist in combination with a single isolated substitutional nitrogen atom.

Předkládaná práce se zabývá návrhem projektorové soustavy transmisního elektronového mikroskopu (TEM) pro metodu single particle analysis (SPA). Návrh projektorové soustavy byl vytvořen v programu Electron Optical Design (EOD) verze 4.020. Série buzení jednotlivých čoček pro zvětšení projektorové soustavy v rozsahu od 50 do 10000 byla vypočítaná pomocí přístupu využívajícího aproximaci tenké čočky, dále pomocí přístupu využívajícího aproximaci tlusté čočky, metodou linearního zaostření v programu EOD a metodou nelineárního zaostření v programu EOD ve verzi 5.003. Dosažené výsledky byly porovnány a ověřeny pomocí reálného trasování částic v programu EOD.

Electron orbital theory was applied to the design of the geometrical structure of an electron multiplier for an image intensifier. A special structure satisfying production requirements was studied. Electron optical calculations consisted of determining the potential distribution and tracing the electron trajectories. Liebmann’s procedure was used to solve Laplace’s equation with constant potentials on the multiplier electrodes as boundary conditions. The trajectories were determined by solving the equation of motion in an electrostatic field using a Runge-Kutta procedure. The initial conditions for the trajectories were the initial energies, initial positions, and the initial directions of the secondary electrons. The plotted trajectories indicated the feasibility of an electron multiplier of the type studied.

Zahlreiche Geräte, die in den Naturwissenschaen, in der Industrie und im Gesundheitswesen unverzichtbar sind, basieren auf Strahlen schneller geladener Teilchen. Dazu zählen unter anderem Elektronen- und Ionenmikroskope, entsprechende Lithographiestrahlanlagen und Röntgenstrahlungsquellen. Magnetische Optiken, die Strahlen geladener Teilchen ablenken, formen und fokussieren, sind das Rückgrat aller Geräte die mit hochenergetischen Teilchen arbeiten, da sie im Vergleich zu Optiken, die auf elektrischen Feldern basieren, bei hohen Teilchengeschwindigkeiten eine überlegene optische Leistung aufweisen. Konventionelle makroskopische magnetische Optiken sind jedoch groß, teuer und platzraubend, nicht hochfrequenzfähig und erfordern aktive (Wasser-)Kühlung zur Wärmeabfuhr. Sie sind daher für Mehrstrahlinstrumente, miniaturisierte Anwendungen und schnelle Strahlmanipulation ungeeignet, die für zukünftige Fortschritte in der Nanofabrikation und -analyse gebraucht werden. Im Rahmen dieser Arbeit wurden die ersten magnetischen selbst-assemblierenden Mikro-Origami-Elektronenoptiken entwickelt, hergestellt und charakterisiert. Mit dem verwendeten Miniaturisierungsansatz können, bei ähnlicher optischer Leistung, alle oben genannten Nachteile von konventionellen magnetischen Optiken überwunden werden. Die außergewöhnlichen Eigenschaften dieser optischen Elemente werden durch die einzigartigen Merkmale der Mikrospulen ermöglicht: geringe Größe, geringe Induktivität und geringer Widerstand. Im Rahmen dieser Arbeit wurden unter anderem adaptive Phasenplaen hergestellt, die Elektronenvortexstrahlen mit einem bislang unerreichten Bahndrehimpuls von bis zu mehreren 1000 ̄h erzeugen. Des Weiteren wurden schnelle Elektronenstrahldeflektoren zur Strahlablenkung, zum zweidimensionalen Rastern und für stroboskopische Experimente gefertigt. Sie besitzen eine Ablenkleistung im mrad-Bereich für 300 kV Elektronen und einen Frequenzdurchgang bis zu 100 MHz. Darüber hinaus wurden miniaturisierte adrupollinsen mit Brennweiten kleiner als 46 mm für 300 kV Elektronen entwickelt. Diese drei Arten elektronenoptischer Elemente sind von großem Interesse für verschiedenste Anwendungen in der Nanofabrikation und -analyse, da sie unter anderem als integrale Bestandteile von zu entwickelnden Mehrstrahlinstrumenten, miniaturisierten Geräten und stroboskopischen Messaufbauten dienen können.:1 Introduction 1.1 Charged Particle Optics 1.2 Miniaturized Charged Particle Optics 1.3 Phase Plates for Transmission Electron Microscopy 2 Charged Particle Optics 2.1 Hamiltonian Formalism 2.2 Gaussian Matrix Optics 2.3 Transfer Matrices of Magnetic Elements 2.3.1 Single Quadrupole 2.3.2 Quadrupole Multiplets 2.3.2.1 Quadrupole Doublet 2.3.2.2 Quadrupole Triplet 2.3.2.3 Higher Order Quadrupole Multiplets 2.4 Scaling Laws for Charged Particle Optics 2.4.1 Thin Film 2.4.2 Electrostatic Scaling Laws 2.4.3 Magnetic Scaling Laws 3 Design and Fabrication of Miniaturized Electron Optics 3.1 Basics of Polymer-Based Self-Assembly Technology 3.2 Basic Coil Design and Magnetic Field Simulations 3.3 CoFeSiB-Pyrex Core-Shell Micro Wires 3.4 Fabrication of Self-Assembled Micro Coil Devices 4 Optical Properties of Self-Assembled Miniaturized Electron Optics 4.1 Electron Vortex Phase Plate 4.1.1 Projected Magnetic Fields 4.1.2 Vortex Beam Characteristics 4.2 Miniaturized Deflector 4.3 Quadrupole Focusing Optic 4.4 High Frequency Characteristics of Self-Assembled Electron Optics 5 Summary and Outlook 5.1 Applications of Electron Vortex Beams with Large OAM 5.2 Optics of Large Optical Power for Pulsed Instruments 5.3 Stroboscopic TEM Measurements 5.4 Miniaturized Wigglers, Undulators and Free Electron Lasers 5.5 Towards Integrated Electron Optical Systems / Beams of highly accelerated charged particles are essential for numerous indispensable devices used throughout natural sciences, industry and the healthcare sector, e.g., electron and ion microscopes, charged particle lithography machines and X-ray radiation sources. Magnetic charged particle optics that deflect, shape and focus high-energy charged particles are the backbone of all such devices, because of their superior optical power compared to electric field optics at large particle velocities. Conventional macroscopic magnetic optics, however, are large, costly and bulky, not high frequency capable and require active cooling for heat dissipation. They are therefore unsuitable for fast beam manipulation, multibeam instrumentation, and miniaturized applications, much desired for future advances in nanofabrication and analysis. The first on-chip micro-sized magnetic charged particle optics realized via a self-assembling micro-origami process were designed, fabricated and characterized within the frame of this work. The utilized micro-miniaturization approach overcomes all the aforementioned obstacles for conventional magnetic optics, while maintaining similar optical power. The exceptional properties of these optical elements are rendered possible by the unique features of strain-engineered micro-coils: small size, small inductance and small resistivity. Within the frame of this work, adaptive phase plates were fabricated, which generate electron vortex beams with an unprecedented orbital angular momentum of up to several 1000 ̄h. Furthermore, fast electron beam deflectors for beam blanking, two-dimensional scanning and stroboscopic experiments were manufactured. They possess a deflection power in the mrad regime for 300 kV electrons and a high frequency passband up to 100 MHz. Additionally, miniaturized strong quadrupole lenses with focal lengths down to 46 mm for 300 kV electrons have been developed. These three types of electron optical elements are of great interest for a wide range of applications in nanofabrication and analysis, as they serve as integral components of future multibeam instruments, miniaturized devices, and stroboscopic measurement setups to be developed.:1 Introduction 1.1 Charged Particle Optics 1.2 Miniaturized Charged Particle Optics 1.3 Phase Plates for Transmission Electron Microscopy 2 Charged Particle Optics 2.1 Hamiltonian Formalism 2.2 Gaussian Matrix Optics 2.3 Transfer Matrices of Magnetic Elements 2.3.1 Single Quadrupole 2.3.2 Quadrupole Multiplets 2.3.2.1 Quadrupole Doublet 2.3.2.2 Quadrupole Triplet 2.3.2.3 Higher Order Quadrupole Multiplets 2.4 Scaling Laws for Charged Particle Optics 2.4.1 Thin Film 2.4.2 Electrostatic Scaling Laws 2.4.3 Magnetic Scaling Laws 3 Design and Fabrication of Miniaturized Electron Optics 3.1 Basics of Polymer-Based Self-Assembly Technology 3.2 Basic Coil Design and Magnetic Field Simulations 3.3 CoFeSiB-Pyrex Core-Shell Micro Wires 3.4 Fabrication of Self-Assembled Micro Coil Devices 4 Optical Properties of Self-Assembled Miniaturized Electron Optics 4.1 Electron Vortex Phase Plate 4.1.1 Projected Magnetic Fields 4.1.2 Vortex Beam Characteristics 4.2 Miniaturized Deflector 4.3 Quadrupole Focusing Optic 4.4 High Frequency Characteristics of Self-Assembled Electron Optics 5 Summary and Outlook 5.1 Applications of Electron Vortex Beams with Large OAM 5.2 Optics of Large Optical Power for Pulsed Instruments 5.3 Stroboscopic TEM Measurements 5.4 Miniaturized Wigglers, Undulators and Free Electron Lasers 5.5 Towards Integrated Electron Optical Systems

The aim of my Master's thesis is the design of a scanning electron microscope. The designed concept presents an innovative approach to the problems and respects all technical, ergonomic and aesthetical demands made on it. The main creative part of design process starting from the concept development and ending up with the final solution is preceded by a background research study including a historical, technical and design analysis of the electron microscope. The conclusion of my Master's thesis analyses the final design, its character and its contribution in broader context.