Wight S A, Zeissler C J
National Institute of Standards and Technology, Gaithersburg, Maryland 20899.
Microsc Res Tech. 1993 Aug;25(5-6):393-7. doi: 10.1002/jemt.1070250507.
This work provides examples of some of the imaging capabilities of environmental scanning electron microscopy applied to easily charged samples relevant to particle analysis. Environmental SEM (also referred to as high pressure or low vacuum SEM) can address uncoated samples that are known to be difficult to image. Most of these specimens are difficult to image by conventional SEM even when coated with a conductive layer. Another area where environmental SEM is particularly applicable is for specimens not compatible with high vacuum, such as volatile specimens. Samples from which images were obtained that otherwise may not have been possible by conventional methods included fly ash particles on an oiled plastic membrane impactor substrate, a one micrometer diameter fiber mounted on the end of a wire, uranium oxide particles embedded in oil-bearing cellulose nitrate, teflon and polycarbonate filter materials with collected air particulate matter, polystyrene latex spheres on cellulosic filter paper, polystyrene latex spheres "loosely" sitting on a glass slide, and subsurface tracks in an etched nuclear track-etch detector. Surface charging problems experienced in high vacuum SEMs are virtually eliminated in the low vacuum SEM, extending imaging capabilities to samples previously difficult to use or incompatible with conventional methods.
这项工作提供了一些环境扫描电子显微镜成像能力的示例，这些能力应用于与颗粒分析相关的易带电样品。环境扫描电子显微镜（也称为高压或低真空扫描电子显微镜）可以处理已知难以成像的未镀膜样品。即使在涂覆导电层后，这些样品中的大多数通过传统扫描电子显微镜也难以成像。环境扫描电子显微镜特别适用的另一个领域是对于与高真空不兼容的样品，例如挥发性样品。通过传统方法原本可能无法获得图像的样品包括涂油塑料膜撞击器基板上的飞灰颗粒、安装在金属丝末端的直径为一微米的纤维、嵌入含油硝酸纤维素中的氧化铀颗粒、带有收集到的空气颗粒物的聚四氟乙烯和聚碳酸酯过滤材料、纤维素滤纸上的聚苯乙烯乳胶球、“松散”放置在载玻片上的聚苯乙烯乳胶球以及蚀刻核径迹蚀刻探测器中的亚表面径迹。在低真空扫描电子显微镜中，高真空扫描电子显微镜中遇到的表面充电问题几乎被消除，从而将成像能力扩展到以前难以使用或与传统方法不兼容的样品。
