Acquisition of a Field Emission Scanning Electron Microscope for Nano- to Microscale Imaging and Chemical Analysis in the College of Engineering, University of Delaware

特拉华大学工程学院（COE）电子显微镜中心正在寻找一种场发射扫描电子显微镜（FESEM），以满足对纳米分辨率扫描电子显微镜的直接、广泛需求。FESEM已成为进行微到纳米形态材料成像和化学成像/分析不可或缺的仪器。重要的是，真正的纳米级数据可以从大量的材料中获得，从“硬”无机物（导电和绝缘）到“软”聚合物和生物制品。与传统的热离子扫描电镜（目前是工程学院（COE） EM设施中唯一有效的扫描电镜）相比，FESEM提供了更高的分辨率（纳米结构直径小至1nm，而我们传统的扫描电镜分辨率在~ 100nm范围内），并且可以在低至0.5kV的电压下工作（传统的热源内部扫描电镜必须在~30kV的电压下工作，才能达到~0.1 mm的最终分辨率）。需要强调的是，这种低加速电压允许对COE和整个大学正在研究的所有材料进行直接纳米级成像和元素分析。在目前的COE SEM仪器JEOL JXA-840上，成像和化学分析仅限于导电无机物，并且只能在相对较低的分辨率下进行（二次电子成像0.1 mm， x射线分析~1.0 mm）。聚合物和其他绝缘材料必须涂上一层厚的（~10纳米）导电金属层才能成像，从而完全掩盖了真实的表面结构和化学成分。由于高真空条件，在传统的扫描电镜环境条件下，具有一定水合程度的生物材料是不可能的。FESEM系统配备了最先进的能量色散x射线光谱和低温转移和冷阶段，用于原位水化（玻璃化）生物材料的成像。随着当前研究范式对纳米技术的重视，当然在UD，这个新的FESEM将填补工程学院研究能力中材料表征的巨大空白。因此，据估计，超过18名教职员工和30至40名研究生将立即从获得FESEM中受益。研究生和高级本科生的教育培训机会对整个大学来说是一个明显的好处。目前，我们的电子显微镜设施为大约30名学生和博士后提供服务，主要用于TEM研究。此外，超过25名来自工程和其他自然科学专业的学生使用该设施进行课程作业（新开设的TEM课程MSEG/CHEG 832和MSEG602中的TEM实验室模块，材料科学与工程专业提供的材料结构实验室）。具体来说，PI将开发一个新的MSEG602实验模块，用于特定的FESEM介绍和指导即将进入工程学院的研究生。FESEM的增加将为不同水平和不同背景的学生提供一个独特的机会，让他们在一个跨学科的先进实验室环境中工作，这是工程学院电子显微镜中心。自2001年夏天以来，我们已经使用我们的JEOL FasTEM系统，包含在FEG2010 TEM显微镜，以加强我们的本科和研究生的课堂教学和培训。FasTEM是一个集成了我们的场发射透射电子显微镜（FE-TEM）的系统，能够通过计算机网络进行通信和远程操作。除了远程演示外，中小学生还经常到实验室进行电子显微镜的内部演示。很明显，这些内部和外部的演示产生了学生对科学技术的好奇心和兴趣。为了更好地实现我们的教育推广目标（并吸引高素质的本科生到大学），我们希望我们也可以用FESEM展示现代工程材料的纳米结构。经验告诉我们，FESEM的三维形态图像比二维TEM数据更吸引K-12学生，二维TEM数据更难解释。此外，2001年秋天，通过探索频道的访问，大众媒体对特拉华大学工程学院的电子显微镜设备进行了重点报道。观察到兴登堡号金属索断裂表面的微观细节，表明了灾难性拉伸破坏的性质。这种类型的大众媒体外展也将在未来进一步追求，在此期间，我们可以突出工程学院电子显微镜设备的新实验能力。

A field emission scanning electron microscope (FESEM) is sought for the University of Delaware College of Engineering (COE) electron microscopy center to fill an immediate, widespread need for nanometer resolution scanning electron microscopy. FESEM has become an indispensable instrument in conducting micro- to nanomorphological material imaging and chemical imaging/analysis. Importantly, true nanoscale data is obtainable from of an immense array of materials, spanning "hard" inorganics, both electrically conductive and insulative, to "soft" polymeric and biologicals. In comparison to traditional thermionic SEM (currenlty, the only functioning SEM in the college of engineering (COE) EM facility), the FESEM provides far superior resolution (nanostructures as small as 1 nm in diameter while our traditional SEM resolution is in the range of ~100 of nm) and can be operated at voltages as low as 0.5kV (the traditional thermal source in-house SEM must operate at ~30kV to reach its ultimate resolution of ~0.1 mm). It is important to stress that this low accelerating voltage allows direct nanoscopic imaging and elemental analysis of all materials currently being studied in COE and across the university. On the current COE SEM instrument, a JEOL JXA-840, imaging and chemical analysis is limited to conductive inorganics and only feasible at relatively low resolution (0.1 mm for secondary electron imaging and ~1.0 mm for x-ray analysis). Polymeric and other insulating materials must be coated by a thick (~10's of nm) layer of conductive metal for feasible imaging which, consequently, completely masks true surface structure and chemistry. Biological materials with some level of hydration are simply not possible at ambient conditions in the traditional SEM due to high vacuum conditions. The sought FESEM system is equipped with state-of-the-art energy dispersive x-ray spectroscopy and a cryogenic transfer and cold stage for imaging of in situ, hydrated (vitrified) biological materials. With the large emphasis on nanotechnology in the current research paradigm, and certainly here at UD, this new FESEM will fill a large materials characterization gap in the college of engineering's research capabilities. Consequently, it is estimated that over 18 faculty members and 30 to 40 graduate students will immediately benefit in their research from the acquisition of the FESEM.Educational training opportunities for graduate students and advanced undergraduates represent a clear benefit to the university as a whole. At present, our electron microscopy facility serves about 30 students and post doctors for predominantly TEM research purposes. In addition, over 25 students from engineering and other natural science majors on campus use the facility for their course work (the new TEM course MSEG/CHEG 832 and the TEM lab module in MSEG602, Structure of Materials lab offered through Materials Science and Engineering). Specifically, a new MSEG602 lab module will be developed by the PI for specific FESEM introduction and instruction to incoming college of engineering graduate students. The addition of an FESEM will provide a unique opportunity for students at various levels and from various backgrounds to work in an interdisciplinary, advanced laboratory setting that is the College of Engineering electron microscopy center. Since the summer of 2001, we have utilized our JEOL FasTEM system, contained in the FEG2010 TEM microscope, to enhance our undergraduate and graduate classroom teaching and training. The FasTEM is a system integrated with our field emission transmission electron microscope (FE-TEM) that is capable of telecommunication and remote operation through computer networks. In addition to remote demonstrations, elementary and middle school students frequently visit the lab for in-house demonstrations of electron microscopy. It is obvious that these in-house and outside demonstrations generate significant student curiosity and interest in science and technology. To better achieve our educational outreach goals (and attract top quality undergraduates to the university) it is our desire that we also can demonstrate the nanostructures of modern engineered materials with an FESEM. Experience tells us that the 3-dimentional morphological images of the FESEM appeal more to K-12 students than 2-dimensional TEM data which is more difficult to interpret. Furthermore, the UD college of engineering electron microscopy facility has been highlighted in the popular media through a visit by the Discovery Channel in the fall of 2001. Microscopic details of fracture surfaces from metal cables of the Hindenberg were observed indicating the nature of catastrophic tensile failure. This type of popular media outreach will also be further pursued in the future during which we can highlight the new experimental capabilities of the college of engineering electron microscopy facility.