Development of TEM specimen Holder Enabling Atomic Level Observation under One Atomospheric Pressure

环境细胞（EC）技术可用于通过透射电子显微镜研究各种环境气氛下的水合和催化样品等。在本研究中，我们开发了一种膜密封型EC，使原子水平下观察一个大气压。所开发的EC具有连接EC和显微镜柱外部的通道，因此，可以通过调节气体流量来控制样品环境的气体压力。通常，EC必须具有用于电子束通过的窗口，并且覆盖窗口的一些密封膜是必要的，以防止气体泄漏到显微镜柱中。EC最重要的组成部分是密封膜。在本研究中，我们成功地制备了20 nm厚的碳膜，它能承受一个大气压或更高的压力。厚度约150 nm的三乙酰纤维素（TAG）膜的缓冲层夹在碳膜和金属支撑网格之间，其非常有效地实现对气体压力差的抵抗。研制了一套插入TEM试样保持器的装置，并成功地在一个大气压下观察到了TiO2粉末样品。通过向样品中引入反应气体，可以在原子尺度上观察TiO2的催化行为。目前正在研究对所实现的分辨率的精确评估，作为大气压力和密封膜厚度的函数。由高速电子入射引起的等离子体有时会对观察到的样品造成损伤，这是基于Monte Cairo计算机模拟的研究。

An environmental cell (EC) technique is useful for the study of hydrated and catalytic specimens etc. under various environmental atmosphere by a transmission electron microscope. In the present study, we have developed a film-sealed type EC which enables atomic level observation under one atmospheric pressure. The developed EC has the passages connecting the EC and the outside of the microscope column, therefore, the gas pressure of the specimen environment can be controlled by adjusting the gas flow. In general, the EC must have some windows for electron beam passage and some sealing films covering the windows are necessary to protect the gas leakage into the microscope column. The most important component of the EC is the sealing film. The film must withstand above atmospheric pressure with maintaining properties such as high electron transmittance, amorphousness of the film and so on. In the present study, we succeeded to make a carbon film of 20 nm thick which,withstands the pressure of one atmospheric pressure or more. A buffer layer of triacetylcellulose (TAG) film of about 150 nm in thickness was sandwiched between the carbon film and the metal supporting grid, which works very effectively to realize the resistance to the gas pressure difference. An apparatus to insert the TEM specimen holder with the EC was also developed and TiO2 powder sample was successfully observed at one atmospheric air pressure. By introducing reaction gas to the sample, catalytic behavior of TiO2 might be possible to observe in atomic scale. Precise evaluation on the achieved resolution is now under examining as a function of the atmospheric pressure and the thickness of the sealing film. Plasma induced by high speed electrons incidence sometimes gave damages to the observed sample, which is under investigation based on Monte Cairo computer simulations.