Imaging of Cathodoluminescence Zoning in Calcite by Scanning Electron Microscopy and Hyperspectral Mapping
Imaging of Cathodoluminescence Zoning in Calcite by Scanning Electron Microscopy and Hyperspectral Mapping
复制标题
通过扫描电子显微镜和高光谱测绘对方解石中的阴极发光分区进行成像
DOI：
--
复制
发表时间：
2005
期刊：
影响因子：
--
通讯作者：
P. Edwards
中科院分区：
文献类型：
--
作者：
Martin R. Lee;R. Martin;C. Trager;P. Edwards
摘要用扫描电子显微镜（SEM）对碳酸盐矿物阴极发光（CL）进行成像是有问题的，因为当电子束在一个区域上扫描时，CL从每个点衰减的速度很慢（磷光现象）。使用SEM-CL和新开发的基于电子探针的高光谱映射技术，我们已经评估了已经提出的克服磷光的方法。使用停留时间技术，电子束静态的持续时间增加，使得来自给定点的CL发射对来自后续点的总信号的贡献可以忽略不计。形成在橙子波长下具有高发光强度的方解石的清晰SEM-CL图像所需的停留时间等于或大于6.4毫秒，而主要在紫外线至蓝色波长下发光的方解石可以使用亚毫秒停留时间成像。通过使用更长的停留时间（> 1000 ms），CL和X射线光谱也可以从每个点采集，以形成高光谱图。有限波长成像技术采用光学滤波器来去除缓慢衰减的长波长发射，使得仅使用更快速衰减的紫外到蓝色波长形成图像，从而允许使用更短的停留时间。这两种技术都有一些缺点。驻留时间技术的主要缺点是获取高分辨率图像所需的时间较长，而有限波长成像的成功可能取决于所使用的CL检测器的灵敏度。CL图像和发射光谱获得的高光谱映射也表明，有一个非线性关系的发光强度变化在紫外线到蓝色的波长和强度变化在橙子波长，表明短波长的发射是一个不完美的代理分区在较长的波长。此外，我们一直无法确定控制紫外线的蓝色发光强度的空间变化，虽然我们的数据折扣Fe 2+浓度作为唯一的决定因素。通过使用高光谱测绘结合电子探针显微分析，以获得CL和X射线光谱从相同的微米大小的体积的材料，现在可以理解和量化的控制激活和淬火的CL在方解石和其他矿物，如磷灰石和锆石。
Abstract Imaging of cathodoluminescence (CL) emission from carbonate minerals by scanning electron microscopy (SEM) is problematic owing to the slow rate at which CL decays from each point as the electron beam is scanned over an area (the phenomenon of phosphorescence). Using SEM-CL and a newly developed electron probe–based technique of hyperspectral mapping, we have evaluated methods that have been proposed to overcome phosphorescence. With the dwell-time technique, the duration of time that the electron beam is static is increased such that CL emission from a given point makes a negligible contribution to the total signal from subsequent points. The dwell-time required to form sharp SEM-CL images of calcite that has a high intensity of luminescence at orange wavelengths is equal to or greater than 6.4 milliseconds, whereas calcite that luminesces predominantly at ultraviolet to blue wavelengths can be imaged using submillisecond dwell times. By using longer dwell times (> 1000 ms), CL and X-ray spectra can also be acquired from each point to form hyperspectral maps. The limited-wavelength imaging technique employs optical filters to excise slowly decaying long-wavelength emission so that the image is formed only using the more rapidly decaying ultraviolet to blue wavelengths, allowing shorter dwell times to be used. Both techniques have some disadvantages. The main drawback of the dwell-time technique is the long period of time required to acquire high-resolution images whereas the success of limited-wavelength imaging may depend on the sensitivity of the CL detector being used. CL images and emission spectra acquired by hyperspectral mapping also show that there is a nonlinear relationship between luminescence intensity variations at ultraviolet to blue wavelengths and intensity variations at orange wavelengths, indicating that short-wavelength emission is an imperfect proxy for zoning at longer wavelengths. Additionally, we have been unable to identify the controls on spatial variations in the intensity of ultraviolet to blue luminescence, although our data discount Fe2+ concentrations as being the sole determinant. By using hyperspectral mapping in combination with electron-probe microanalysis to obtain CL and X-ray spectra from the same micrometer-sized volume of a material, it is now possible to understand and quantify the controls on activation and quenching of CL in calcite and other minerals such as apatite and zircon.