Ning Yanxiao, Fu Qiang, Li Yifan, Zhao Siqin, Wang Chao, Breitschaft Martin, Hagen Sebastian, Schaff Oliver, Bao Xinhe
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, the Chinese Academy of Sciences, Dalian 116023, China.
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, the Chinese Academy of Sciences, Dalian 116023, China.
Ultramicroscopy. 2019 May;200:105-110. doi: 10.1016/j.ultramic.2019.02.028. Epub 2019 Mar 2.
Photoemission electron microscopy (PEEM) is a powerful surface technique for dynamic imaging of surface processes while PEEM studies have been performed under ultrahigh vacuum or high vacuum conditions. Here we report on a near ambient pressure PEEM (NAP-PEEM) instrument, which enables high resolution PEEM imaging in near ambient pressure (> 1 mbar) gases over a wide temperature range (150 - 1200 K). Installed with an electron gun near ambient pressure low energy electron microscopy (NAP-LEEM) can be achieved as well. The success of this new NAP-PEEM/LEEM instrument relies on the following key design concepts. First, a two-stage accelerating electric field consisting of a low field region between sample and intermediate electrode ("nozzle") and a high field between nozzle and objective lens. Second, a three-stage differential pumping system allowing a near ambient pressure atmosphere at the sample surface while ultrahigh vacuum maintained in the imaging lens systems. Third, a unique NAP cell with gas inlet/outlet, light illumination, sample cooling/heating, and precise sample positioning. The new technique will have important applications in surface catalysis, thin film growth, and energy conversion devices under nearly realistic working conditions.
光发射电子显微镜（PEEM）是一种用于表面过程动态成像的强大表面技术，而此前的PEEM研究都是在超高真空或高真空条件下进行的。在此，我们报告一种近常压光发射电子显微镜（NAP-PEEM）仪器，它能够在近常压（>1毫巴）气体中、在很宽的温度范围（150 - 1200 K）内实现高分辨率的PEEM成像。通过安装电子枪，还可以实现近常压低能电子显微镜（NAP-LEEM）。这种新型NAP-PEEM/LEEM仪器的成功依赖于以下关键设计理念。第一，一个两级加速电场，由样品与中间电极（“喷嘴”）之间的低场区以及喷嘴与物镜之间的高场区组成。第二，一个三级差动抽气系统，能使样品表面保持近常压气氛，同时在成像透镜系统中维持超高真空。第三，一个独特的NAP样品池，具备气体进出口、光照、样品冷却/加热以及精确的样品定位功能。这项新技术将在近乎实际的工作条件下，在表面催化、薄膜生长和能量转换装置等方面有重要应用。
