Enabling Lab-in-Gap Transmission Electron Microscopy at Atomic Resolution
Xiao Feng Zhang Hitachi High Technologies America , 5960 Inglewood Drive , Suite 200 , Pleasanton , CA 94588
xiao.zhang@hitachi-hta.com
Abstract: Hitachi Lab-in-Gap transmission electron microscopy (TEM) technologies are introduced. The term Lab-in-Gap refers to a special
function that allows in situ and in operando TEM studies of materials in gas or liquid environments while stimulations, such as thermal or
electrical fi elds, are applied to the specimen sitting in the pole piece gap in a TEM system. Physical or chemical process can be activated and imaged in real time using TEM or other imaging modes. The new generation environmental TEM platform with large pole piece gap and advanced aberration correctors opens wide possibilities for integrat- ing multiple stimuli sources as well as large-area, sub-Å resolution live imaging for dynamic structural changes.
Introduction
In February 2014, the Basic Energy Sciences Division of Department of Energy held a workshop on Future of Electron Scattering and Diff raction [ 1 ]. T e goal of the workshop was to identify the frontiers in electron scattering and diff raction that address the grand challenges in chemistry, material science, physics, and biology. T e workshop partici- pants concluded there were four key areas where the next generation instrumentation would have major impacts. One of them was the Lab-In-Gap type of microscope. T e name of Lab-In-Gap is for a special type of microscope that allows in situ and in operando microscopy study of materials in gas or liquid environments while other stimulation fi elds such as thermal or electrical fi elds are applied to specimen. In particular, Lab-In-Gap refers to enabling physical or chemical lab work in the pole-piece gap of the electron microscope; the microscope serves as a real-time observation tool to reveal the ongoing dynamic processes such as chemical reactions on an unprecedented atomic-spatial-resolution level if modern techniques are employed.
For a transmission electron microscopy (TEM) system, an electromagnetic objective lens focuses an electron beam of say 60 to 300 kV. An important design for the electro- magnetic objective lens is the upper and lower pole pieces with a gap between them. T e pole piece gap allows one to insert a TEM specimen and objective aperture into the symmetrical magnetic fi eld ( Figure 1 ). T e key concept for the Lab-In-Gap microscope is to take full advantage of the pole piece gap, namely building miniaturized devices or reaction cells in the pole piece gap. In order to do so, modifi cation of existing TEM products is required in many aspects. For example, on one hand, the pole piece gap is usually made very narrow, typically less than 5 mm, to guarantee a high imaging resolution, which is a core value of the TEM. On the other hand, suffi cient room is needed in the gap to add functional devices or measurement mechanisms around the TEM specimen to mimic what can be done in a physical or chemical lab. Another challenge is the sample environment. When a stimulus is applied to specimen in a TEM column, the dynamic response of the specimen structure can be observed
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in real time using TEM; this is called in situ TEM observation. In situ TEM technology has a long history [ 2 ]. Many in situ TEM datasets reflect some process that is happening in high vacuum, and these data may or may not directly correlate to what would happen in the real world. The environment in the real world consists of gas and liquid. Ideally, when doing an in situ TEM study, a gas or liquid environment should also be available in the TEM specimen area. It is clear that the Lab-In-Gap electron microscope should provide a gas or liquid environment, a large space in the pole piece gap, mechanisms for stimulation of the specimen, and sensors for measuring the effects. Even with all these modifications, the microscope should still be able to deliver high-resolution images. For today’s materials research, atomic resolution is a minimum requirement, and sub-Å resolution is highly desired.
Current Hitachi Lab-In-Gap TEM Technologies and Examples
Hitachi has been developing and manufacturing in situ and environmental TEM technologies and platforms for two decades. T e two famous early stage Lab-in-Gap types of Hitachi TEM systems are the 300 kV model H-9000; one was installed at Argonne National Laboratory, Illinois, and another at the IBM T omas J. Watson Research Center at Yorktown Heights, New York. T e one at Argonne National Laboratory has a special design in which an ion beam is introduced from
Figure 1 : Schematic illustration of objective lens structure used for a TEM system (not to scale). The lens is composed of upper and lower pole pieces. The TEM specimen is loaded in the pole piece gap.
doi: 10.1017/S1551929515000930
www.microscopy-today.com • 2016 January
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