Advanced Characterisation of Black Silicon by Electron Microscopy Techniques

Black silicon (BSi) is a branch of silicon material whose surface is specially processed to a micro-/nano-scale structure, which inherits most of the advantages of bulk silicon material and possesses some unique optical, electronic, and electrochemical properties that originate from its distinctive surface geometry. BSi is a highly versatile material with properties that can be tuned by changing the surface morphology during the fabrication process. The diverse range of BSi surface morphology enables it to suit the requirements for many applications in the semiconductor industry, such as high-efficiency solar cells, biosensors, photocathodes, or as an anode for lithium batteries. However, the complex nature of BSi surface morphology poses challenges to the current state-of-art surface-related characterisation methods. This thesis will focus on the accurate characterisation for BSi surface morphology and surface dopant profiles. For a surface with micro-/nano-structure morphology, the most established surface topographical method is atomic force microscopy (AFM). However, AFM is not able to probe highly roughened BSi with near-vertical features or overhanging structures. An improved method to accurately extract the BSi morphology is first demonstrated in this thesis, enabling the BSi three-dimensional (3D) surface data to be extracted with high precision over a surface area of up to 320 µm2. This method is based on an automated Xe+ plasma focused ion beam (PFIB) and scanning electron microscopy (SEM) tomography technique. This thesis provides guidelines from sample preparation to optimized post-data processing procedures. For characterising surface dopant profiles, standard dopant profiling techniques can neither properly probe the highly textured BSi surface nor provide a two-dimensional (2D) dopant map. An optimized method based on scanning electron microscopy (SEM) quantitative 2D dopant contrast imaging (SEMDCI) is thoroughly investigated in this thesis. This method utilises SEM under imaging conditions optimized to primarily show the voltage contrast arising from the surface work function. The optimized SEMDCI procedure enables quantitative resolution of the doping level derived from the signal intensity. It can therefore provide the spatial distribution of dopant profiles for complex nano/microtextured surfaces such as BSi. This work provides comprehensive methodology guidelines for BSi-related characterisation that offer suitable measurement accuracy for simulation input. In this thesis, two highly reliable characterisation methods are developed for BSi, offering an in-depth understanding of BSi material properties, and providing insightful design guidelines for BSi semiconductor devices fabrication

Nuclear Fusion Programme: Annual Report of the Association Karlsruhe Institute of Technology/EURATOM ; January 2013 - December 2013 (KIT Scientific Reports ; 7671)

The Karlsruhe Institute of Technology (KIT) is working in the framework of the European Fusion Programme on key technologies in the areas of superconducting magnets, microwave heating systems (Electron-Cyclotron-Resonance-Heating, ECRH), the deuterium-tritium fuel cycle, He-cooled breeding blankets, a He-cooled divertor and structural materials, as well as refractory metals for high heat flux applications including a major participation in the preparation of the international IFMIF project

Development of new approaches for assessing miscibility and the solid state structure of olanzapine dispersions in polymeric carriers

Drug-polymer dispersions are a well-established formulation strategy, with many commercial products utilising this technology to either increase bioavailability of poorly water soluble compounds or produce controlled release systems. The main limitation of these formulations is their long-term physical stability since these systems are often unstable supersaturated molecular dispersions. This instability can lead to recrystallisation of the drug, potentially affecting the dissolution performance. In this work, new analytical methods were applied to provide understanding into the crystallisation behaviour of a model drug, olanzapine, in several polymer dispersions. The intention was to develop new insights into the physical drivers for crystallisation, the means by which it can be detected and predicted, and the possibility of utilising this knowledge to manipulate the crystal form. Olanzapine-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles were initially produced. The physical stability of this system was assessed through drug-polymer solubility measurements. Several de-mixing approaches were compared in which supersaturated dispersions were recrystallised to achieve the equilibrium solubility level of the drug in the polymer phase. During this work a quasi-isothermal modulated temperature differential scanning calorimetry (QiMTDSC) protocol was developed and applied to study crystallisation in these systems. Drug-polymer solubility was successfully measured using this approach and drug crystallisation could also be monitored, allowing investigation of the conditions under which the solubility equilibrium could be achieved. Olanzapine is a polymorphic molecule and the study of its recrystallisation in PLGA dispersions highlighted that standard techniques could not determine which form was crystallising. Thus, a new simultaneous differential scanning calorimetry-powder X-ray diffraction (DSC-PXRD) method was applied to characterise olanzapine crystallisation in several polymer dispersions. Interestingly, drug crystallisation was influenced by the different polymers present. A new polymorph, olanzapine form IV, was discovered which indicated that this crystallisation approach can be used as an alternative method for polymorph screening. A process was developed to extract form IV crystals from the polymer matrix, providing the proof-of-concept that this approach can be used to generate and isolate new polymorphic forms

MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications

Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described

Generalized averaged Gaussian quadrature and applications

A simple numerical method for constructing the optimal generalized averaged Gaussian quadrature formulas will be presented. These formulas exist in many cases in which real positive GaussKronrod formulas do not exist, and can be used as an adequate alternative in order to estimate the error of a Gaussian rule. We also investigate the conditions under which the optimal averaged Gaussian quadrature formulas and their truncated variants are internal