Structural analysis of molecular nanostructures and thin films

Phthalocyanines (Pcs) form crystals whose structure and morphology depend on the growth conditions, leading to changes in the physical properties which are still little understood. Pc thin films and nanostructures have already been exploited in optoelectronic applications and could form the basis of spintronic devices but little or contradictory structural information is available because they are challenging systems to study. Hence the precise determination of the molecular order in these systems is of considerable interest both from a fundamental and technological point of view but requires a combination of complementary techniques. Crystalline powders of α-copper phthalocyanine (CuPc), α-metal-free phthalocyanine (H2Pc) and their mixtures are studied using powder X-ray diffraction (XRD) and found to be isomorphous and adopt a triclinic structure first proposed for α-CuPc (Hoshino et al., 2003). This information is used to study highly textured crystalline α-Pc thin films. The texture reduces the available crystallographic information but allows for the manipulation of the anisotropic physical properties. The Pc molecular plane lies 82±11° to the substrate when deposited on a weakly interacting substrate but at 7 or 9±5° when templated by a layer of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA). Such an interpretation is different to all those previously given. The change in the texture is confirmed by high resolution transmission electron microscopy (HRTEM) of ultramicrotomed cross-sections of the films. The optimum TEM operating conditions were first determined on sections of CuPc single crystals which demonstrated an information limit of ~5Å with HRTEM. The technique was then applied to the films and the morphology, crystallinity and texturing of the layers is largely retained by the sectioning process. With further refinements it is hoped that this technique could be used to study the properties of interfaces and individual domains in multilayers and blends of organic thin films. Lastly the crystal structure of a new CuPc phase designated as η which forms nanowires as thin as 10nm and shows enhanced absorption in the infra-red (IR) is proposed. XRD, transmission electron diffraction (TED) and lattice potential energy (LPE) minimisation were used to determine the crystal structure: monoclinic P21/a, Z = 2, a = 24.8±0.2Å, b = 3.77±0.02Å, c = 13.2±0.1Å and β = 106±1°. The LPE minimisation was validated by correctly predicting the atomic coordinates of β-CuPc to within 0.05Å

Mapping sub-surface structure of thin films in three dimensions with an optical near-field

Subsurface mapping is crucial to understanding many biological systems as well as structured thin films for (opto)electronic or photonic applications. A non‐invasive method is presented to map subsurface nanostructures from scanning near‐field optical microscopy images. The Bethe–Bouwkamp model is used to simulate imaging of buried nano‐objects or subsurface slanted planar interfaces, and it is shown how to determine their depth and size, or the interface inclination, from just one image. It is shown that the steep optical field gradient makes near‐field microscopy a particularly sensitive depth probe for thin films

Structural analysis of molecular nanostructures and thin films

Phthalocyanines (Pcs) form crystals whose structure and morphology depend on the growth conditions, leading to changes in the physical properties which are still little understood. Pc thin films and nanostructures have already been exploited in optoelectronic applications and could form the basis of spintronic devices but little or contradictory structural information is available because they are challenging systems to study. Hence the precise determination of the molecular order in these systems is of considerable interest both from a fundamental and technological point of view but requires a combination of complementary techniques. Crystalline powders of α-copper phthalocyanine (CuPc), α-metal-free phthalocyanine (H2Pc) and their mixtures are studied using powder X-ray diffraction (XRD) and found to be isomorphous and adopt a triclinic structure first proposed for α-CuPc (Hoshino et al., 2003). This information is used to study highly textured crystalline α-Pc thin films. The texture reduces the available crystallographic information but allows for the manipulation of the anisotropic physical properties. The Pc molecular plane lies 82±11° to the substrate when deposited on a weakly interacting substrate but at 7 or 9±5° when templated by a layer of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA). Such an interpretation is different to all those previously given. The change in the texture is confirmed by high resolution transmission electron microscopy (HRTEM) of ultramicrotomed cross-sections of the films. The optimum TEM operating conditions were first determined on sections of CuPc single crystals which demonstrated an information limit of ~5Å with HRTEM. The technique was then applied to the films and the morphology, crystallinity and texturing of the layers is largely retained by the sectioning process. With further refinements it is hoped that this technique could be used to study the properties of interfaces and individual domains in multilayers and blends of organic thin films. Lastly the crystal structure of a new CuPc phase designated as η which forms nanowires as thin as 10nm and shows enhanced absorption in the infra-red (IR) is proposed. XRD, transmission electron diffraction (TED) and lattice potential energy (LPE) minimisation were used to determine the crystal structure: monoclinic P21/a, Z = 2, a = 24.8±0.2Å, b = 3.77±0.02Å, c = 13.2±0.1Å and β = 106±1°. The LPE minimisation was validated by correctly predicting the atomic coordinates of β-CuPc to within 0.05Å.EThOS - Electronic Theses Online ServiceEPSRCGBUnited Kingdo

An Exploration of the Colonial Perception of Indigenous Life

Our project is a zine discussing the MacLeod Gazette article entitled “Arrest of the Indian Cattle Killers.” The zine covers the history of the Stoney-Nakoda people, life in the Morleyville area, Indigenous-settler relations and perceptions, Treaty 7, and the involvement of the McDougall family with the Indigenous people of the area. The zine delivers an enriching micro-history surrounding the perception of Indigenous culture under a colonial lens. How it affected the Indigenous community then andhow it carries out now

Orientation effects in copper phthalocyanine films studied by electron paramagnetic resonance spectroscopy

This article performs an analysis of current limitations regarding the extraction of parallel behavioral models to reproduce the power amplifier (PA) nonlinear behavior and its dynamics. To overcome these limitations, a general preprocessing block that clearly improves the identification capabilities shown by classical parallel structures is proposed. It follows the principle of separating both static and dynamic nonlinear behavior of the PA to obtain a better identification performance. A comparison with common parallel configurations using linear estimation is performed, to highlight the benefits of using the preprocessing structure. Furthermore, a new nonlinear parallel structure using sub-band filtering techniques is also proposed. For the models extraction and comparison, four types of noise-free simulated data presenting different levels of nonlinearities and memory, as well as a measured signal obtained from a laboratory amplifier have been considered.TARGET - IST-1-507893-NOECAPES-BrazilSpanish Government (MICINN) - TEC2008-06684-C03-0