Larcheri Silvia, Rocca Francesco, Jandard Frank, Pailharey Daniel, Graziola Roberto, Kuzmin Alexei, Purans Juris
CNR-IFN, Istituto di Fotonica e Nanotecnologie, Unità FBK-CeFSA di Trento, Via alla Cascata 56/C, 38100 Trento, Italy.
Rev Sci Instrum. 2008 Jan;79(1):013702. doi: 10.1063/1.2827485.
Investigations of complex nanostructured materials used in modern technologies require special experimental techniques able to provide information on the structure and electronic properties of materials with a spatial resolution down to the nanometer scale. We tried to address these needs through the combination of x-ray absorption spectroscopy (XAS) using synchrotron radiation microbeams with scanning near-field optical microscopy (SNOM) detection of the x-ray excited optical luminescence (XEOL) signal. This new instrumentation offers the possibility to carry out a selective structural analysis of the sample surface with the subwavelength spatial resolution determined by the SNOM probe aperture. In addition, the apex of the optical fiber plays the role of a topographic probe, and chemical and topographic mappings can be simultaneously recorded. Our working XAS-SNOM prototype is based on a quartz tuning-fork head mounted on a high stability nanopositioning system; a coated optical fiber tip, operating as a probe in shear-force mode; a detection system coupled with the microscope head control system; and a dedicated software/hardware setup for synchronization of the XEOL signal detection with the synchrotron beamline acquisition system. We illustrate the possibility to obtain an element-specific contrast and to perform nano-XAS experiments by detecting the Zn K and W L(3) absorption edges in luminescent ZnO and mixed ZnWO(4)-ZnO nanostructured thin films.
对现代技术中使用的复杂纳米结构材料进行研究，需要特殊的实验技术，这些技术要能够提供材料结构和电子特性的信息，且空间分辨率要低至纳米尺度。我们试图通过将使用同步辐射微束的X射线吸收光谱（XAS）与X射线激发光致发光（XEOL）信号的扫描近场光学显微镜（SNOM）检测相结合来满足这些需求。这种新仪器能够以由SNOM探针孔径确定的亚波长空间分辨率对样品表面进行选择性结构分析。此外，光纤尖端起到形貌探针的作用，并且可以同时记录化学和形貌映射图。我们的工作型XAS - SNOM原型基于安装在高稳定性纳米定位系统上的石英音叉头；作为剪切力模式下探针的涂覆光纤尖端；与显微镜头控制系统耦合的检测系统；以及用于将XEOL信号检测与同步辐射光束线采集系统同步的专用软件/硬件设置。我们通过检测发光ZnO和混合ZnWO₄ - ZnO纳米结构薄膜中的Zn K和W L₃吸收边，展示了获得元素特异性对比度并进行纳米XAS实验的可能性。
