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迫切、广泛的需求。场发射扫描电子显微镜已经成为进行微到纳米形态材料成像和化学成像/分析不可缺少的工具。重要的是，真正的纳米级数据可以从大量的材料中获得，从导电和绝缘的“硬”无机物到“软”的聚合物和生物制品。与传统的热离子扫描电子显微镜(目前是工程学院(COE)EM设备中唯一有效的扫描电子显微镜)相比，FESEM提供了高得多的分辨率(直径小至1 nm的纳米结构，而我们的传统扫描电子显微镜分辨率在~100 nm的范围内)，并且可以在低至0.5KV的电压下操作(传统的热源内部扫描电子显微镜必须在~30KV下操作才能达到~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和整个大学目前正在研究的所有材料进行直接纳米成像和元素分析。在目前的COE扫描电子显微镜仪器JEOL JXA-840上，成像和化学分析仅限于导电无机物，并且仅在相对较低的分辨率下可行(0.1 mm用于二次电子成像，~1.0 mm用于X射线分析)。聚合物和其他绝缘材料必须覆盖一层厚的(约10‘S纳米)导电金属层才能进行成像，因此，完全掩盖了真实的表面结构和化学成分。在传统扫描电子显微镜的环境条件下，由于高真空条件，具有一定程度水合的生物材料是不可能的。SEEED FESEM系统配备了最先进的能量色散X射线光谱仪和低温转移和冷台，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高度重视，当然在UD这里，这个新的FESEM将填补工程学院研究能力中的一个巨大的材料表征空白。因此，预计超过18名教职员工和30至40名研究生将立即从获得FESE的研究中受益。为研究生和高级本科生提供教育培训机会对整个大学来说是明显的好处。目前，我们的电子显微镜设备为大约30名学生和博士后提供服务，主要用于电子显微镜研究目的。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学习(新的瞬变电磁课程MSEG/CHEG 832和MSEG602中的瞬变电磁实验模块，材料科学与工程提供的材料结构实验室)。具体地说，PI将开发一个新的MSEG602实验模块，用于向即将入学的工程学院研究生介绍和指导特定的FESEM。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，在一个跨学科的高级实验室环境中工作，这就是工程学院的电子显微镜中心。自2001年夏季以来，我们一直利用FEG2010透射电子显微镜中包含的JEOL FasTEM系统来加强本科和研究生的课堂教学和培训。FasTEM是与我们的场发射透射式电子显微镜(FE-TEM)集成的系统，能够通过计算机网络进行远程通信和操作。除了远程演示外，中小学生还经常来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激发了学生对科学和技术的极大好奇心和兴趣。为了更好地实现我们的教育扩展目标(并吸引高质量的本科生进入大学)，我们希望我们还可以用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的瞬变电磁数据更吸引K-12学生，后者更难解释。此外，通过探索频道在2001年秋季的一次访问，UD工程学院的电子显微镜设施在大众媒体上得到了突出的报道。观察到兴登堡号金属电缆断口的微观细节，表明了灾难性拉伸破坏的性质。未来还将进一步开展这类大众媒体宣传活动，在此期间，我们可以突出工程学院电子显微镜设施的新实验能力。

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.