Dry etching is an important technique for pattern transferin fabrication of most opto-electronic devices, since it canprovide good control of both structure size and shape even on asub-micron scale. Unfortunately, this process step may causedamage to the material which is detrimental to deviceperformance. It is therefore an objective of this thesis todevelop and investigate low damage etching processes for InPbased devices. An ion beam system in combination with hydrocarbon (CH4) based chemistries is used for etching. At variousion energies and gas flows the etching is performed in twomodes, reactive ion beam etching (RIBE) and chemical assistedion beam etching (CAIBE). How these conditions affect both etchcharacteristics (e.g. etch rates and profiles, surfacemorphology and polymer formation) and etch induced damage (onoptical and electrical properties) is evaluated and discussed.Attention is also paid to the effects of typical post etchingtreatments such as annealing on the optical and electricalproperties. An important finding is the correlation betweenas-etched surface morphology and recovery/degradation inphotoluminescence upon annealing in PH3. Since this type of atmosphere is typical forcrystal regrowth (an important process step in III/Vprocessing) a positive result is imperative. A low ion energy N2/CH4/H2CAIBE process is developed which not onlysatisfies this criteria but also exhibits good etchcharacteristics. This process is used successfully in thefabrication of laser gratings. In addition to this, the abilityof the ion beam system to modify the surface morphology in acontrollable manner is exploited. By exposing such modifiedsurfaces to AsH3/PH3, a new way to vary size and density of InAs(P)islands formed on the InP surfaces by the As/P exchangereaction is presented. This thesis also proposes a new etch chemistry, namelytrimethylamine ((CH3)3N or TMA), which is a more efficient methyl sourcecompared to CH4because of the low energy required to break the H3C-N bond. Since methyl radicals are needed for theetching it is presumably a better etching chemistry. A similarinvestigation as for the CH4chemistry is performed, and it is found that bothin terms of etch characteristics and etch induced damage thisnew chemistry is superior. Extremely smooth morphologies, lowetch induced damage and an almost complete recovery uponannealing can be obtained with this process. Significantly,this is also so at relatively high ion energies which allowshigher etch rates. <b>Keywords:</b>InP, dry etching, ion beam etching, RIBE,CAIBE, hydrocarbon chemistry, trimethylamine, As/P exchangereaction, morpholoy, low damage, AFM, SCM, annealing

Materials prepared on the nanoscale often exhibit many different properties compared to the same materials in their bulk-state. Interest in nanostructured materials has increased because of these properties in fields such as microelectronics, catalysis, optics and sensors. This increased interest in nanostructured materials calls for new and more precise fabrication techniques. This thesis describes how to use the porous anodic aluminium oxide as a template for the fabrication of a variety of nanostructured materials. Palladium and copper nanoparticles were deposited along the pore walls in anodic aluminum oxide using electroless deposition and atomic layer deposition. In both cases, it was possible to control the size of the nanoparticles by carefully monitoring the deposition parameters. The thesis also describes how Prussian blue nanoparticles and nanotubes can be fabricated using the anodic aluminium oxide as a template. The deposition of Prussian blue was performed by a sequential wet-chemical method. By using atomic layer deposition, it was also possible to deposit thin films of amorphous Nb2O5 on the pore walls. When the template was removed by etching, freestanding nanotubes were obtained. The anodic aluminium oxide membrane was also used as a mask for high energy (MeV) ion irradiation of an underlying substrate. The tracks produced were etched away with hydrogen fluoride. In this way, it was possible to transfer the highly ordered porous pattern from the mask onto other oxides such as SiO2 and TiO2. All fabricated structures were characterized using a variety of analysis techniques: scanning electron microscopy for evaluating sample morphology; transmission electron microscopy for better resolved investigations of the morphology; X-ray diffraction to assess crystallinity; energy dispersive spectroscopy and X-ray fluorescence spectroscopy to determine the elemental composition and identify possible contaminants. The general aim of the work described in this thesis has been to create a set of tools for use in the fabrication of a variety of nanostructured materials, whose dimensions composition can be tailored by selecting appropriate fabrication methods and parameters.

The utilization of ferromagnetic shape memory alloys (FSMAs) in small scale devices has attracted considerable attention within the last decade. However, the lack of sufficient studies on their reversible shape change mechanisms, i.e, superelasticity, magnetic field-induced martensite variant reorientation and martensitic phase transformation, at the micron and submicron length scales prevent the further development and the use of FSMAs in small scale devices. Therefore, investigating the size effects in these mechanisms has both scientific and technological relevance. Superelastic behavior of Ni54Fe19Ga27 shape memory alloy single crystalline pillars was studied under compression as a function of pillar diameter. Multiple pillars with diameters ranging between 200 nm and 10 µm were cut on a single crystalline bulk sample oriented along the [110] direction in the compression axis and with fully reversible two-stage martensitic transformation. The results revealed size dependent two-stage martensitic transformation which was suppressed for pillar sizes of 1 µm and below. We also demonstrated that the reduction in pillar diameter decreases the transformation temperature due to the difficulty of martensite nucleation in small scales. Size effects in the magnetic field-induced martensite variant reorientation were investigated in the Ni50Mn28.3Ga21.7 single crystals oriented along the [100] direction of the austenite phase. Single crystalline compression pillars were fabricated on the martensite twins between the sizes of 630 nm and 20 µm. It was found that the stress-induced and magnetic field-induced martensite variant reorientation are size dependent and became more difficult with the reduction in sample size. Surprisingly, it was still possible to magnetically activate the shape change in the micropillars which indicates the fact that magnetocrystalline anisotropy energy increases with the reduction in sample dimensions. Ni45Mn36.6Co5In13.4 pillars between the 600 nm and 10 µm diameters were investigated along the [100] direction of the austenite to study the size effects in the magnetic field-induced phase transformation (MFIPT). MFIPT was obtained down to 5 µm size in these pillars with reasonable magnetic field levels similar to their bulk counterparts.

Eine der drei Säulen der Krebsbehandlung ist die Strahlentherapie. Einer der neuesten Ansätze hierbei ist die Bestrahlung mit Ionen, zurzeit insbesondere Protonen und Kohlenstoffionen. Diese Hochpräzisionstherapie erfordert ein hohes Maß an Kontrolle, da die applizierte Dosisverteilung sehr empfindlich von Dichteveränderungen im durchstrahlten Gewebe abhängt. Das bisher einzige klinisch eingesetzte Verfahren zur in vivo Überwachung der Dosisapplikation bei Ionenbestrahlungen ist die Positronen-Emissions-Tomographie (PET). Sie ermöglicht eine Verifikation der Teilchenreichweite sowie der Lage des Bestrahlungsfeldes. Die mit der PET-Methode gemessene Aktivitätsverteilung lässt sich jedoch nicht direkt mit der geplanten Dosisverteilung vergleichen. Daher ist eine Vorherberechnung der erwarteten Aktivitätsverteilung auf der Grundlage des Bestrahlungsplanes notwendig, welche dann mit der Messung verglichen wird und eine qualitative Beurteilung der Bestrahlung ermöglicht. Die Vorherberechnung der erwarteten Aktivitätsverteilung erfordert bislang die Kenntnis einer Vielzahl von Wirkungsquerschnitten. Nur für wenige dieser Wirkungsquerschnitte liegen jedoch Messdaten im benötigten Energiebereich und mit ausreichender Genauigkeit vor. Daher verwenden viele Monte-Carlo-Simulationen intrinsische Kernmodelle oder semi-empirische Modellierungen, die häufig eine unzureichende Genauigkeit aufweisen. In Fachkreisen ist bisher noch nicht geklärt, welches die optimale Ionensorte für die Tumortherapie ist. Insbesondere Lithiumionen weisen aufgrund ihrer physikalischen und radiobiologischen Eigenschaften ein großes Potenzial auf. Auch für Bestrahlungen mit diesen Ionen ist ein PET-Monitoring der Therapie erstrebenswert. In der vorliegenden Arbeit wird zunächst die Anwendbarkeit der Reichweite-Verifikation mittels PET bei Bestrahlung mit Lithiumionen gezeigt. Des Weiteren wird ein Konzept zur Modellierung der Positronenemitter-Verteilung ohne Kenntnis der Wirkungsquerschnitte entwickelt. Diese Vorhersage beruht auf in Referenzmaterialien (Wasser, Graphit und Polyethylen) gemessenen tiefenabhängigen Positronenemitter-Yields, mit welchen durch geeignete Linearkombination die Verteilung der Positronenemitter in beliebigen Materialien bekannter Stöchiometrie vorausberechnet werden kann. Die Anwendbarkeit des Yield-Konzeptes wird gezeigt für Lithium- und Kohlenstoffbestrahlungen homogener Polymethylmethacrylat (PMMA) Targets sowie verschiedener inhomogener Targets.

Eine ortsauflösende Spannungs- und Dehnungssensortechnik soll durch die Nutzung magnetostriktiver Materialien auf der Oberfläche von Kohlenstoffeinzelfasern (C-Fasern) und Mikrofeinstrukturierung dieser Schichten erzeugt und zur elektronischen Überwachung des Belastungszustandes von sicherheits- oder servicerelevanten Faserverbundbauteilen eingesetzt werden. Eine auf lokaler Gasphasenabscheidung und Mikrostrukturierung mittels der Focused Ion Beam (FIB)-Technik beruhende Sensorfabrikationsmethode wurde gemeinsam mit dem Institut für Mikrotechnologie Hannover (imt) entwickelt. Mehrschichtig mittels CVD und PVD bedampfte und zusätzlich galvanisch beschichtete C-Fasern weisen neuartige Eigenschaften auf, die im vorgestellten Vorhaben am Lehrstuhl für Verbundwerkstoffe (LVW) charakterisiert wurden. Insbesondere die Untersuchung der verschiedenen Schichten sowie deren Interfaces nehmen eine bedeutende Rolle ein.

No description available.

<p>Dry etching is an important technique for pattern transferin fabrication of most opto-electronic devices, since it canprovide good control of both structure size and shape even on asub-micron scale. Unfortunately, this process step may causedamage to the material which is detrimental to deviceperformance. It is therefore an objective of this thesis todevelop and investigate low damage etching processes for InPbased devices.</p><p>An ion beam system in combination with hydrocarbon (CH₄) based chemistries is used for etching. At variousion energies and gas flows the etching is performed in twomodes, reactive ion beam etching (RIBE) and chemical assistedion beam etching (CAIBE). How these conditions affect both etchcharacteristics (e.g. etch rates and profiles, surfacemorphology and polymer formation) and etch induced damage (onoptical and electrical properties) is evaluated and discussed.Attention is also paid to the effects of typical post etchingtreatments such as annealing on the optical and electricalproperties. An important finding is the correlation betweenas-etched surface morphology and recovery/degradation inphotoluminescence upon annealing in PH₃. Since this type of atmosphere is typical forcrystal regrowth (an important process step in III/Vprocessing) a positive result is imperative. A low ion energy N₂/CH₄/H₂CAIBE process is developed which not onlysatisfies this criteria but also exhibits good etchcharacteristics. This process is used successfully in thefabrication of laser gratings. In addition to this, the abilityof the ion beam system to modify the surface morphology in acontrollable manner is exploited. By exposing such modifiedsurfaces to AsH₃/PH₃, a new way to vary size and density of InAs(P)islands formed on the InP surfaces by the As/P exchangereaction is presented.</p><p>This thesis also proposes a new etch chemistry, namelytrimethylamine ((CH₃)₃N or TMA), which is a more efficient methyl sourcecompared to CH₄because of the low energy required to break the H₃C-N bond. Since methyl radicals are needed for theetching it is presumably a better etching chemistry. A similarinvestigation as for the CH₄chemistry is performed, and it is found that bothin terms of etch characteristics and etch induced damage thisnew chemistry is superior. Extremely smooth morphologies, lowetch induced damage and an almost complete recovery uponannealing can be obtained with this process. Significantly,this is also so at relatively high ion energies which allowshigher etch rates.</p><p><b>Keywords:</b>InP, dry etching, ion beam etching, RIBE,CAIBE, hydrocarbon chemistry, trimethylamine, As/P exchangereaction, morpholoy, low damage, AFM, SCM, annealing</p>

In der vorliegenden Arbeit werden elementare, plasma-relevante Ion-Molekül-Reaktionen in der Gasphase mit einer Guided Ion Beam (GIB)-Apparatur untersucht. Es werden Geschwindigkeitsverteilungen und absolute integrale Reaktionsquerschnitte für die Produkte der Reaktionen 40Ar+/36Ar+ + 40Ar und N2+ + CH4/CD4 für Stoßenergien zwischen 0.1 und 3.5 eV angegeben. Die Ergebnisse lassen Rückschlüsse auf die Dynamik der reaktiven Stöße zu. Bei dem resonanten, symmetrischen Ladungstransferprozeß können 40Ar+-Primär- und Produkt-Ionen aufgrund ihrer unterschiedlichen Flugzeit getrennt nachgewiesen werden. Bei der quasi-resonanten, nicht-symmetrischen Reaktion wird ein isotopenselektierter 36Ar+-Ionenstrahl verwendet, um den Nachweis von 40Ar+-Produkten nicht zu beeinträchtigen. Die Geschwindigkeitsverteilungen dieser Produkte zeigen einen zusätzlichen Anteil von Ionen, die im Schwerpunktsystem vorwärts gestreut werden. Alle Ausgangskanäle der Reaktion N2+ + CX4 (X = H, D) wurden experimentell nachgewiesen. Aus den gemessenen integralen Querschnitten ergibt sich CX3+ als das häufigste Produkt mit einem Anteil von über 85%. Protonierte Produkte werden gegenüber deuterierten bevorzugt. Geschwindigkeitsverteilungen zeigen, daß die Produkte sowohl aus dem Zerfall eines langlebigen Zwischenkomplexes als auch durch einen direkten Prozeß gebildet werden. Oberhalb einer Stoßenergie von 0.5 eV überwiegt der direkte Prozeß. Es wird kein Unterschied im Reaktionsmechanismus von protonierten und deuterierten Produkten gleicher Art festgestellt.

In der vorliegenden Arbeit wurden Messungen zur Multiphotonenanregung von HCl durchgeführt. Die untersuchten Moleküle wurden dabei in einem Molekularstrahl innerhalb eines Vierpols durch Laserlicht variabler Wellenlänge angeregt. Bei verlustfreier Führung im Vierpol konnten die dabei entstandenen Ionen anhand ihrer Flugzeit bestimmt werden. Die Aufnahme von Wellenlängenspektren für einzelne Massen ermöglichte die Bestimmung der am Zerfall des Moleküls beteiligten resonanten Zwischenzustände. Eine Analyse der Flugzeitspektren der Protonen führte zu genaueren Aussagen über die vorliegenden Zerfallskanäle. Der Schwerpunkt dieser Arbeit wurde dabei auf die Ionenpaarbildung, H+ + Cl-, gelegt.

Uranium-zirconium (U-Zr) alloys comprise a class of metallic nuclear fuel that is regularly considered for application in fast nuclear energy systems. The U-10wt%Zr alloy has been demonstrated to very high burnup without cladding breach in the Experimental Breeder Reactor-II (EBR-II). This was accomplished by successfully accommodating gaseous fission products with low smear density fuel and an enlarged cladding plenum. Fission gas swelling behavior of the fuel has been experimentally revealed to be significantly affected by the temperature gradient within a fuel pin and the multiple phase morphologies that exist across the fuel pin. However, the phase effects on swelling behavior have not been yet fully accounted for in existing fuel performance models which tend to assume the fuel exists as a homogeneous single phase medium across the entire fuel pin. Phase effects on gas bubble nucleation and growth in the alloy were investigated using transmission electron microscopy (TEM). To achieve this end, a comprehensive examination of the alloy system was carried out. This included the fabrication of uranium alloys containing 0.1, 2, 5, 10, 20, 30, 40, and 50 wt% zirconium by melt-casting. These alloys were characterized using electron probe micro-analysis (EPMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Once the alloys were satisfactorily characterized, selected U-Zr alloys were irradiated with 140 keV He^(+) ions at fluences ranging from 1 × 10^(14) to 5 × 10^(16) ions/cm^(2). Metallographic and micro-chemical analysis of the alloys indicated that annealing at 600 °C equilibrates the alloys within 168 h to have stable α-U and δ-UZr_(2) phase morphologies. This was in contrast to some reported data that showed kinetically sluggish δ-UZr_(2) phase formation. Phase transformation temperatures and enthalpies were measured using DSC-TGA for each of the alloys. Measured temperatures from different time annealed alloys have shown consistent matches with most of the features in the current U-Zr phase diagram which further augmented the EPMA observed microstructural equilibrium. Nevertheless, quantitative transformation enthalpy analysis also suggests potential errors in the existing U-Zr binary phase diagram. More specifically, the (β-U, γ2) phase region does not appear to be present in Zr-rich (> 15 wt%) U-Zr alloys and so further investigation may be required. To prepare TEM specimens, characterized U-Zr alloys were mechanically thinned to a thickness of ~150 μm, and then electropolished using a 5% perchloric acid/95% methanol electrolyte. Uranium-rich phase was preferentially thinned in two phase alloys, giving saw-tooth shaped perforated boundaries; the alloy images were very clear and alloy characterization was accomplished. During in-situ heating U-10Zr and U-20Zr alloys up to 810 °C, selected area diffraction (SAD) patterns were observed as the structure evolved up to ~690 °C and the expected α-U → β-U phase transformation at 662 °C was never observed. For the temperature range of the (α-U, γ2) phase region, phase transformation driven diffusion was observed as uranium moved into Zr-rich phase matrix in U-20Zr alloy; this was noted as nonuniform bridging of adjacent phase lamellae in the alloy. From the irradiation tests, nano-scale voids were discovered to be evenly distributed over several micrometers in U-40Zr alloys. For the alloys irradiated at the fluences of 1 × 10^(16) and 5 × 10^(16) ions/cm^(2), estimated void densities were proportional to the irradiation doses, (250 ± 40) and (1460 ± 30) /μm^(2), while void sizes were fairly constant, (6.0 ± 1.5) and (5.2 ± 1.2) nm, respectively. Measured data could be foundational inputs to the further development of a semi-empirical metal fuel performance model.