Advanced optical micro-imaging methods for determining the structural and chemical state of materials: development of, and access to equipment

研究材料的发光发射特性可以在理解产生发光的过程方面获得丰厚的回报，提供有关材料矩阵中可能存在的缺陷的存在和性质的丰富信息。应用广泛，例如，作为光电器件技术重要材料开发的重要组成部分，到岩石的地质年代测定。根据样品被激发的方式，发光光子能够携带有关其起源的信息。如果用同步加速器光探测材料基体中存在的原子的核心能级，就可以分析发射光子的材料的化学和结构，因为光子携带着宿主的x射线吸收特征。因此，x射线吸收光谱（OD-XAS）的光学检测可能是材料科学研究中最重要的测量方法之一，因此需要在样品的发光特性与其结构和化学之间建立直接和明确的联系。此外，在非均质样品的情况下，提供x射线吸收特征和光发射的空间分辨率的能力是必不可少的。通常，这种XAS成像需要高度复杂的同步加速器光束线仪器。然而，在OD-XAS中存在另一种更灵活的可能性：由于x射线吸收光谱可以通过可见光子发射获得，这意味着原则上可以采用相对简单的光学显微镜方法来确定样品表面的化学和结构的空间变化。2005年，EPSRC提供资金建造了一种独特的仪器，CLASSIX（通过微成像x射线吸收的表面化学发光和结构），以利用这种优雅的XAS成像替代方案。事实证明，这项投资是非常值得的，该仪器在一个真正的多学科领域产生了丰厚的红利，并建立了一个富有开发价值的新科学领域。目前申请赠款的基础是若干有关问题的汇合。2008年，达斯伯里的同步加速器辐射源将在运行26年后关闭。然而，CLASSIX的需求在不断增长，在2008年之后，这种便携式仪器将需要前往欧洲各地的同步加速器，包括英国的钻石光源。由于最初的CLASSIX是第一代原型设计主要用于达斯伯里实验室的主场，因此需要升级以使这种国际机动性可行。然而，这也为新测量方法的整合提供了一个理想的机会，这些方法自建造以来的2年使用中已经确定，包括(i)增加拉曼微成像能力，以补充微成像x射线吸收光谱，（ii）用先进的快速扫描系统取代慢扫描发射单色仪进行图像分析，（iii）离线x射线激发样品表面的设施。CLASSIX（和它的非成像对应物mole）将在2008年中期从达斯伯里大学转移到阿伯里斯特威斯大学，在那里它将成为不断发展的研究活动的重要组成部分。然而，对于许多英国研究小组来说，对这种独特仪器的需求仍然很高。因此，这个应用程序为适度的投资提供了理由，以促进离线和在线研究对CLASSIX（和mole）的持续开放访问，并实现上述升级。这将使英国巩固和加强其目前在这些快速发展的分析方法的世界领先地位。

Studying the luminescence emission properties of materials can be richly rewarding in terms of understanding the processes that give rise to light emission, providing a wealth of information concerning the presence and nature of defects that may be present within the material matrix. Applications are widespread from, for example, being an essential component in the development of technologically important materials for optoelectronic devices, to the geological dating of rocks. Depending on how a sample is excited, luminescent photons are capable of carrying with them information about their origin. If the core-levels of the atoms present in the material matrix are probed with synchrotron light, the chemistry and structure of the material from which the photon was emitted can be analysed, since the photons carry with them the X-ray absorption signatures of the host. Optical detection of x-ray absorption spectroscopy (OD-XAS) is therefore potentially one of the most important measurement methods available for materials science research, whereby a direct and unequivocal link needs to be established between the luminescent properties of a sample, and its structure and chemistry. Furthermore, in the case of heterogeneous samples, the ability to provide spatial resolution of the x-ray absorption signatures and optical emission is essential. Normally, such XAS imaging requires highly sophisticated synchrotron beam-line instrumentation. However, in OD-XAS lies an alternative and much more flexible possibility: since x-ray absorption spectra are available via the visible photon emission, this means that, in principle, relatively simple optical microscopy methods can be deployed to determine the spatial variation of the chemistry and structure of a sample's surface. In 2005, EPSRC provided funds for the construction of a unique instrument, CLASSIX (Chemistry Luminescence And Structure of Surfaces via micro-Imaging X-ray absorption) to exploit this elegant XAS imaging alternative. The investment has turned out to be extremely worthwhile, with the instrument yielding rich dividends in a truly multi-disciplinary arena, and establishing a new science area rich for exploitation. The basis for the current grant application derives from a convergence of a number of relevant issues. In 2008, the synchrotron radiation source at Daresbury will close after 26 years of operation. However, CLASSIX is in rising demand, and after 2008, this portable instrument will need to travel to synchrotrons across Europe, including the Diamond Light Source in the UK. As the original CLASSIX was a first generation prototype designed for use primarily at its home ground of Daresbury Laboratory, there is need for an upgrade to make this international mobility feasible. However, this also provides an ideal opportunity for the incorporation of new measurement methods that have been identified during the 2 years usage since construction, including (i) the addition of Raman micro-imaging capability, to complement the micro-imaged X-ray absorption spectroscopy, (ii) the replacement of the slow-scanning emission monochromator with advanced rapid-scan systems for image analysis and (iii) facilities for off-line x-ray excitation of the sample surfaces.CLASSIX (and its non-imaging counterpart MOLES), will transfer from Daresbury to Aberystwyth University mid-way in 2008, where it will be an essential component of the evolving research activities there. However, the demand for this unique instrument remains high for many UK research groups. This application thus makes the case for a modest investment to facilitate the continuing open access to CLASSIX (and MOLES) for both off-line and on-line research, and to implement the upgrades identified above. This will allow the UK to consolidate and enhance its current world-lead in these rapidly-evolving analysis methods.