Dual-species quantum degeneracy of potassium-40 and rubidium-87 on an atom chip

In this article we review our recent experiments with a 40K-87Rb mixture. We demonstrate rapid sympathetic cooling of a 40K-87Rb mixture to dual quantum degeneracy on an atom chip. We also provide details on efficient BEC production, species-selective magnetic confinement, and progress toward integration of an optical lattice with an atom chip. The efficiency of our evaporation allows us to reach dual degeneracy after just 6 s of evaporation - more rapidly than in conventional magnetic traps. When optimizing evaporative cooling for efficient evaporation of 87Rb alone we achieve BEC after just 4 s of evaporation and an 8 s total cycle time.Comment: 8 pages, 4 figures. To be published in the Proceedings of the 20th International Conference on Atomic Physics, 2006 (Innsbruck, Austria

Highly Plasma Etch-Resistant Photoresist Composition Containing a Photosensitive Polymeric Titania Precursor

A composition is derived from an addition polymerizable organotitanium polymer which upon exposure to an oxygen plasma or baking in air, is converted to titanium dioxide (titania) or is converted to a mixed, titanium-containing metal oxide. The metal oxide formed in situ imparts etch- resistant action to a patterned photoresist layer. The composition may also be directly deposited and patterned into permanent metal oxide device features by a photolithographic process

Wetting in Color

Colorimetric litmus tests such as pH paper have enjoyed wide commercial success due to their inexpensive production and exceptional ease of use. However, expansion of colorimetry to new sensing paradigms is challenging because macroscopic color changes are seldom coupled to arbitrary differences in the physical/chemical properties of a system. In this thesis I present in detail the development of Wetting in Color Technology, focusing primarily on its application as an inexpensive and highly selective colorimetric indicator for organic liquids. The technology exploits chemically-encoded inverse-opal photonic crystals to control the infiltration of fluids to liquid-specific spatial patterns, projecting minute differences in liquids’ wettability to macroscopically distinct, easy-to-visualize structural color patterns. It is shown experimentally and corroborated with theoretical modeling using percolation theory that the high selectivity of wetting, upon-which the sensitivity of the indicator relies, is caused by the highly symmetric structure of our large-area, defect-free $SiO_2$ inverse-opals. The regular structure also produces a bright iridescent color, which disappears when infiltrated with liquid naturally coupling the optical and fluidic responses. Surface modification protocols are developed, requiring only silanization and selective oxidation, to facilitate the deterministic design of an indicator that differentiates a broad range of liquids. The resulting tunable, built-in horizontal and vertical chemistry gradients allow the wettability threshold to be tailored to specific liquids across a continuous range, and make the readout rely only on countable color differences. As wetting is a generic fluidic phenomenon, Wetting in Color technology could be suitable for applications in authentication or identification of unknown liquids across a broad range of industries. However, the generic nature of the response also ensures chemical non-specificity. It is shown that combinatorial measurements from an array of indicators add a degree of chemical specificity to the platform, which can be further improved by monitoring the drying of the inverse-opal films. While colorimetry is the central focus of this thesis, applications of this platform in encryption, fluidics and nanofabrication are also briefly explored.Engineering and Applied Science

On Hardness of the Joint Crossing Number

The Joint Crossing Number problem asks for a simultaneous embedding of two disjoint graphs into one surface such that the number of edge crossings (between the two graphs) is minimized. It was introduced by Negami in 2001 in connection with diagonal flips in triangulations of surfaces, and subsequently investigated in a general form for small-genus surfaces. We prove that all of the commonly considered variants of this problem are NP-hard already in the orientable surface of genus 6, by a reduction from a special variant of the anchored crossing number problem of Cabello and Mohar

Investigations on reactively driven ion beam etching procedures for improvement of optical aluminium surfaces

Das reaktiv gesteuerte Ionenstrahlätzen von optischen Aluminiumoberflächen bietet einen vielversprechenden Prozessansatz, um Formfehlerkorrektur, Glättung periodischer Drehstrukturen und die Reduzierung von Rauheitsmerkmalen im Ortsfrequenzbereich der Mikrorauheit in einer Technologie zu kombinieren. Diese Arbeit konzentriert sich auf die experimentelle Analyse der niederenergetischen Ionenbestrahlung von einkorn-diamantgedrehten, technischen Aluminiumlegierungen RSA Al6061 und RSA Al905. Die Ionenstrahlbearbeitung unter Verwendung der Prozessgase Sauerstoff und Stickstoff ermöglicht eine direkte Oberflächenformfehlerkorrektur bis zu 1 µm Bearbeitungstiefe unter Beibehaltung der Ausgangsrauheit. Die sich aus dem vorangegangenen Formgebungsverfahren, dem Einkorn-diamantdrehen, ergebende Drehmarkenstruktur schränkt allerdings häufig die Anwendbarkeit dieser Spiegeloberflächen im kurzwelligen Spektralbereich ein. Daher wurde im Rahmen dieser Arbeit ein zweistufiger Prozessablauf entwickelt, um eine weitere Verbesserung der Oberflächenrauheit zu erreichen. Durch die Ionenstrahl-Planarisierungstechnik unter Verwendung einer Opferschicht werden die im hohen Ortsfrequenzbereich liegenden Drehmarken erfolgreich um insgesamt 82 % reduziert. Eine Kombination mit anschließender, direkter Ionenstrahlglättung zur nachfolgenden Verbesserung der Mikrorauigkeit wird vorgestellt. Um die Prozessführung in einem industrietauglichen Rahmen zu etablieren, wurden die experimentellen Untersuchungen mit einer 13,56 MHz betriebenen Hochfrequenz-Ionenquelle durchgeführt, konnten aber auch erfolgreich auf eine Breitstrahl-Ionenquelle vom Typ Kaufman übertragen werden.:Bibliographische Beschreibung iv Danksagung vi Table of Contents viii 1 Introduction 1 2 Surface engineering with energetic ions 8 2.1 Ion target interactions during ion beam erosion 8 2.2 Ion beam finishing methods 10 2.2.1 Ion beam figuring 11 2.2.2 Ion beam planarization 12 2.2.3 Ion beam smoothing 14 3 Experimental set-up and analytical methods 15 3.1 Experimental set-up 15 3.2 Kaufman-type broad beam ion source 18 3.3 Materials 19 3.3.1 Aluminium alloy materials 19 3.3.2 Photoresist materials as planarization layer 21 3.4 Surface topography error regimes 22 3.5 Analytical Methods 23 3.5.1 Analysis of surface roughness 23 3.5.1.1 White light interferometry (WLI) 23 3.5.1.2 Atomic force microscopy (AFM) 25 3.5.1.3 Power spectral density (PSD) analysis 27 3.5.2 Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) 29 3.5.3 X-ray photoelectron spectroscopy (XPS) 31 3.5.4 Time of flight- secondary ion mass spectrometry (ToF-SIMS) 32 3.5.5 Reflectometry 34 3.5.6 Photoresist composition 35 3.5.6.1 Attenuated total reflection infrared spectroscopy (ATR-IR) 35 3.5.6.2 Thermogravimetric analysis (TGA) 36 3.5.6.3 Differential scanning calorimetry (DSC) 38 3.5.6.4 Gas chromatography coupled mass spectrometry (GC-MS) 39 4 Surface engineering by reactive ion beam etching 41 4.1 Reactive ion beam etching with nitrogen 41 4.1.1 Dependence of the aluminium alloy composition 42 4.1.2 Ion beam etching of Al905 44 4.2 Local smoothing by reactive ion beam etching 50 4.2.1 Local surface error slope dependent sputter erosion 51 4.2.2 RIBE O2 direct smoothing 56 4.2.2.1 Oxygen finishing at 1.5 keV 56 4.2.2.2 Oxygen finishing at 0.6 keV 62 4.3 Conclusions 66 5 Technological aspects on photoresist preparation for ion beam planarization 69 5.1 Selection of a suitable photoresist 69 5.2 Photoresist application steps 71 5.2.1 DUV exposure of the photoresist layer 72 5.2.2 Postbake: the influence of the amount of organic solvent 73 5.2.3 Postbake: the influence of the baking temperature 74 5.3 Influence of process gas composition 77 5.3.1 Influence on roughness evolution during ion beam irradiation of the photoresist layer 78 5.3.2 Dependency of the process gas on the selectivity 79 5.4 Influence of the ion energy on the selectivity 80 5.5 Ion beam irradiation of the photoresist layer with nitrogen at different material removal depths 81 5.6 Conclusions 82 6 Ion beam planarization of optical aluminium surfaces RSA Al6061 and RSA Al905 84 6.1 Photoresist application on SPDT aluminium alloys 84 6.2 Ion beam planarization 85 6.2.1 Iterative nitrogen processing of RSA Al905 86 6.2.2 Iterative nitrogen processing of RSA Al6061 90 6.3 Ion beam direct smoothing 93 6.3.1 RIBE O2 smoothing of RSA Al905 93 6.3.2 RIBE O2 smoothing of RSA Al6061 97 6.4 Conclusions 101 7 Process transfer to a Kaufman-type broad beam ion source 103 7.1 RIBE machining investigations on RSA Al905 103 7.2 Ion beam planarization of RSA Al6061 106 7.3 Ion beam incidence angle dependent sputtering 107 7.4 Conclusions 113 8 Summary 115 9 Conclusions and Outlook 123 A List of abbreviations 127 B Selected properties of photoresist materials 129 References 131Reactively driven ion beam etching of optical aluminium surfaces provides a promising process route to combine figure error correction, smoothing of periodically turning structures and roughness features situated in the microroughness regime within one technology. This thesis focuses on experimental analysis of low-energy ion beam irradiation on single-point diamond turned technical aluminium alloys RSA Al6061 and RSA Al905. Reactively driven ion beam machining using oxygen and nitrogen process gases enables the direct surface error correction up to 1 µm machining depth while preserving the initial roughness. However, the periodic turning mark structures, which result from preliminary device shaping by single-point diamond turning, often limit the applicability of mirror surfaces in the short-periodic spectral range. Hence, during this work a two-step process route was developed to attain further improvement of the surface roughness. Within the ion beam planarization technique with the aid of a sacrificial layer, the turning marks situated in the high spatial frequency range are successfully reduced by overall 82 %. A combination with subsequently applied direct ion beam smoothing procedure to perform a subsequent improvement of the microroughness is presented. In order to establish the process control in an industrial framework, the experimental investigations were performed using a 13.56 MHz radio frequency ion source, but the developed process routes are also successfully transferred to a broad-beam Kaufman-type ion source.:Bibliographische Beschreibung iv Danksagung vi Table of Contents viii 1 Introduction 1 2 Surface engineering with energetic ions 8 2.1 Ion target interactions during ion beam erosion 8 2.2 Ion beam finishing methods 10 2.2.1 Ion beam figuring 11 2.2.2 Ion beam planarization 12 2.2.3 Ion beam smoothing 14 3 Experimental set-up and analytical methods 15 3.1 Experimental set-up 15 3.2 Kaufman-type broad beam ion source 18 3.3 Materials 19 3.3.1 Aluminium alloy materials 19 3.3.2 Photoresist materials as planarization layer 21 3.4 Surface topography error regimes 22 3.5 Analytical Methods 23 3.5.1 Analysis of surface roughness 23 3.5.1.1 White light interferometry (WLI) 23 3.5.1.2 Atomic force microscopy (AFM) 25 3.5.1.3 Power spectral density (PSD) analysis 27 3.5.2 Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) 29 3.5.3 X-ray photoelectron spectroscopy (XPS) 31 3.5.4 Time of flight- secondary ion mass spectrometry (ToF-SIMS) 32 3.5.5 Reflectometry 34 3.5.6 Photoresist composition 35 3.5.6.1 Attenuated total reflection infrared spectroscopy (ATR-IR) 35 3.5.6.2 Thermogravimetric analysis (TGA) 36 3.5.6.3 Differential scanning calorimetry (DSC) 38 3.5.6.4 Gas chromatography coupled mass spectrometry (GC-MS) 39 4 Surface engineering by reactive ion beam etching 41 4.1 Reactive ion beam etching with nitrogen 41 4.1.1 Dependence of the aluminium alloy composition 42 4.1.2 Ion beam etching of Al905 44 4.2 Local smoothing by reactive ion beam etching 50 4.2.1 Local surface error slope dependent sputter erosion 51 4.2.2 RIBE O2 direct smoothing 56 4.2.2.1 Oxygen finishing at 1.5 keV 56 4.2.2.2 Oxygen finishing at 0.6 keV 62 4.3 Conclusions 66 5 Technological aspects on photoresist preparation for ion beam planarization 69 5.1 Selection of a suitable photoresist 69 5.2 Photoresist application steps 71 5.2.1 DUV exposure of the photoresist layer 72 5.2.2 Postbake: the influence of the amount of organic solvent 73 5.2.3 Postbake: the influence of the baking temperature 74 5.3 Influence of process gas composition 77 5.3.1 Influence on roughness evolution during ion beam irradiation of the photoresist layer 78 5.3.2 Dependency of the process gas on the selectivity 79 5.4 Influence of the ion energy on the selectivity 80 5.5 Ion beam irradiation of the photoresist layer with nitrogen at different material removal depths 81 5.6 Conclusions 82 6 Ion beam planarization of optical aluminium surfaces RSA Al6061 and RSA Al905 84 6.1 Photoresist application on SPDT aluminium alloys 84 6.2 Ion beam planarization 85 6.2.1 Iterative nitrogen processing of RSA Al905 86 6.2.2 Iterative nitrogen processing of RSA Al6061 90 6.3 Ion beam direct smoothing 93 6.3.1 RIBE O2 smoothing of RSA Al905 93 6.3.2 RIBE O2 smoothing of RSA Al6061 97 6.4 Conclusions 101 7 Process transfer to a Kaufman-type broad beam ion source 103 7.1 RIBE machining investigations on RSA Al905 103 7.2 Ion beam planarization of RSA Al6061 106 7.3 Ion beam incidence angle dependent sputtering 107 7.4 Conclusions 113 8 Summary 115 9 Conclusions and Outlook 123 A List of abbreviations 127 B Selected properties of photoresist materials 129 References 13

On Graph Crossing Number and Edge Planarization

Given an n-vertex graph G, a drawing of G in the plane is a mapping of its vertices into points of the plane, and its edges into continuous curves, connecting the images of their endpoints. A crossing in such a drawing is a point where two such curves intersect. In the Minimum Crossing Number problem, the goal is to find a drawing of G with minimum number of crossings. The value of the optimal solution, denoted by OPT, is called the graph's crossing number. This is a very basic problem in topological graph theory, that has received a significant amount of attention, but is still poorly understood algorithmically. The best currently known efficient algorithm produces drawings with $O(\log^2 n)(n + OPT)$ crossings on bounded-degree graphs, while only a constant factor hardness of approximation is known. A closely related problem is Minimum Edge Planarization, in which the goal is to remove a minimum-cardinality subset of edges from G, such that the remaining graph is planar. Our main technical result establishes the following connection between the two problems: if we are given a solution of cost k to the Minimum Edge Planarization problem on graph G, then we can efficiently find a drawing of G with at most \poly(d)\cdot k\cdot (k+OPT) crossings, where $d$ is the maximum degree in G. This result implies an O(n\cdot \poly(d)\cdot \log^{3/2}n)-approximation for Minimum Crossing Number, as well as improved algorithms for special cases of the problem, such as, for example, k-apex and bounded-genus graphs

Planar hexagonal meshing for architecture

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