Development of new methods for the characterization of bio and nanomaterials

通常使用场发射透射电子显微镜（FE-TEM）以1 nm量级的空间分辨率对材料的微观结构进行表征。该表征包括使用X射线微量分析的定量化学分析、使用电子衍射测定晶体结构以及使用电子能量损失谱（EELS）测定原子键的性质。FE-TEM要求样品必须对电子束透明。制备用于FE-TEM观察的薄箔可能是一个漫长而繁琐的过程。然而，由于据报道，快二次电子（FSE）可以降低分辨率的X射线显微分析在FE-TEM的定量轻元素，这种技术的最终分辨率仍然是一个问题。俄歇电子最近被报道具有潜在的相同效果。自20世纪90年代中期以来，场发射扫描电子显微镜（FE-SEM）在市场上可用。低电压FE-SEM具有2nm的图像分辨率。由于FE-SEM的样品制备比FE-TEM更容易，这解释了低电压FE-SEM的日益普及。此外，用于FE-TEM观察的透明薄膜的可观察面积为0.25 其中插入FE-SEM中的抛光样本的面积约为1cm 2。因此，在FE-SEM中可观察到的面积比在TEM中大400，000，000倍，导致关于给定材料的微观结构的非常优越的上级统计信息。然而，FE-TEM可以确定纳米材料的微观结构在三维使用电子断层扫描和软件开发，以提高其空间分辨率。该项目将开发科学软件，使FE-SEM能够对异质材料进行化学定量X射线分析，通过模拟电子背散射衍射图案确定其晶体结构，并开发用于软X射线光谱的新X射线探测器。FSE和俄歇电子对X射线显微分析的影响和一种新的层析成像方法也将被开发用于FE-TEM。

Characterization of the microstructure of materials with a spatial resolution of the order of 1 nm is normally performed using field emission transmission electron microscopy (FE-TEM). This characterization includes quantitative chemical analysis using x-ray microanalysis, the determination of the crystalline structure with electron diffraction and the nature of the atomic bonds using electron energy loss spectroscopy (EELS). FE-TEM requires specimens that must be transparent to the electron beam. Preparing thin foils for FE-TEM observation can be a long and tedious process. However, since it was reported that Fast Secondary Electrons (FSE) can degrade the resolution of X-Ray microanalysis in FE-TEM for the quantification of light elements, the ultimate resolution of this technique is still an issue. Auger electrons were reported recently to have potentially the same effect. Since the mid 1990's, the Field Emission Scanning Electron Microscope (FE-SEM) are available on the market. Low voltage FE-SEM has an image resolution of 2 nm. Since specimen preparation is easier in FE-SEM than in FE-TEM, this explains the increasing popularity of low voltage FE-SEM. Also, transparent thin films for FE-TEM observations have an observable area of 0.25 where polished specimens inserted in the FE-SEM have area of the order of 1cm2. Therefore the area observable in the FE-SEM is 400,000,000 greater than in the TEM, leading to vastly superior statistical information about the microstructure of a given material. However, FE-TEM can determine the microstructure of nanomaterials in three dimension using electron tomography and software development is needed to improve its spatial resolution. This project will develop the scientific software that will allow FE-SEM to perform chemical quantitative x-ray analysis of heterogeneous materials, to determine their crystalline structure by simulating electron backscattered diffraction patterns and to develop a new x-ray detector for soft x-ray spectroscopy. The effect of FSE and Auger electrons on x-ray microanalysis and a new tomography method will also be developed for the FE-TEM.