Browsing by Author "Karimi, O."

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    An approach to high-throughput X-ray diffraction analysis of combinatorial polycrystalline thin film libraries
    (Blackwell Publishing Ltd, 2009-04-30T00:00:00Z) Roncallo, S.; Karimi, O.; Rogers, Keith; Lane, David W.; Ansari, S. A.
    With the demand for higher rates of discovery in the materials field, characterization techniques that are capable of rapidly and reliably surveying the characteristics of large numbers of samples are essential. A chemical combinatorial approach using thin films can provide detailed phase diagrams without the need to produce multiple, individual samples. This is achieved with compositional gradients forming high-density libraries. Conventional raster scanning of chemical or structural probes is subsequently used to interrogate the libraries. A new, alternative approach to raster scanning is introduced to provide a method of high-throughput data collection and analysis using an X-ray diffraction probe. Libraries are interrogated with an extended X-ray source and the scattering data collected using an area detector. A simple technique of 'partitioning' this scattering distribution enables determination of information comparable to conventional raster scanned results but in a dramatically reduced collection time. The technique has been tested using synthetic X-ray scattering distributions and those obtained from contrived samples. In all cases, the partitioning algorithm is shown to be robust and to provide reliable data; discrimination along the library principal axis is shown to be similar to 500 mm and the lattice parameter resolution to be similar to 10(-3) A angstrom mm(-1). The limitations of the technique are discussed and future potential applications described.
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    ItemOpen Access
    The production and characterisation of inorganic combinatorial libraries
    (Cranfield University, 2010-10) Karimi, O.; Rogers, Prof K.
    With the increasing demand for research into new materials, techniques which are able to produce and characterise a large number of samples rapidly are becoming indispensable. Thin film technology has the potential to improve the amount of information contained on deposited samples by creating compositionally graded libraries. Conventionally, raster scan methods are used to interrogate such libraries. The production of combinatorial samples by methods not previously employed in this role has been carried out. Both solution based electrochemical deposition and electrostatic spray vaporisation production methods have been successfully modified to produce thin film continuous compositional spread (CCS) samples. Additional samples have been produced by off-axis direct current magnetron sputtering, a method already established in the combinatorial field. Presented here is a different approach to provide high-throughput data collection and analysis of combinatorial libraries using an X-ray diffraction (XRD) probe. An extended X-ray beam was used to illuminate the polycrystalline libraries and a large area detector used to collect the data. A new partitioning algorithm has been employed to analyze the collected data and extract the crystallographic information from the illuminated area. The results of the technique have been compared with the raster scans showing that the algorithm provides reliable data equivalent to multiple point data collections with significantly increased data acquisition speed. With the new chemical libraries and other simplified samples the partitioning method has been shown to be appropriate for the analysis of both distinct composition high density chemical libraries and also CCS samples. To achieve the validation of the new method the new libraries have been illumination with the extended beam X-ray source. The resultant superimposed diffraction patterns are partitioned with the novel software and compared with conventional XRD. The resolution of the partitioning method has been shown to be in the 1 mm range when applied to CCS libraries and 1.5 mm for high density chemical libraries. For randomly orientated polycrystalline samples the d-spacing change between the partitioned data and the corresponding raster scanned data is not statistically significant. This corresponds to d-spacing determination with a precession of < 0.01 Å when used with the Bruker D8 diffractometer and our geometry.