Development of a multifunctional TEM specimen holder equipped with a piezodriving probe and a laser irradiation port

Perspective and prospects of in situ transmission/scanning transmission electron microscopy

In situ transmission/scanning transmission electron microscopy (TEM/STEM) measurements have taken a central stage for establishing structure-chemistry-property relationship over the past couple of decades. The challenges for realizing 'a lab-in-gap', i.e. gap between the objective lens pole pieces, or 'a lab-on-chip', to be used to carry out experiments are being met through continuous instrumental developments. Commercially available TEM columns and sample holder, that have been modified for in situ experimentation, have contributed to uncover structural and chemical changes occurring in the sample when subjected to external stimulus such as temperature, pressure, radiation (photon, ions and electrons), environment (gas, liquid and magnetic or electrical field) or a combination thereof. Whereas atomic resolution images and spectroscopy data are being collected routinely using TEM/STEM, temporal resolution is limited to millisecond. On the other hand, better than femtosecond temporal resolution can be achieved using an ultrafast electron microscopy or dynamic TEM, but the spatial resolution is limited to sub-nanometers. In either case, in situ experiments generate large datasets that need to be transferred, stored and analyzed. The advent of artificial intelligence, especially machine learning platforms, is proving crucial to deal with this big data problem. Further developments are still needed in order to fully exploit our capability to understand, measure and control chemical and/or physical processes. We present the current state of instrumental and computational capabilities and discuss future possibilities.

Time-resolved transmission electron microscopy for nanoscale chemical dynamics

The ability of transmission electron microscopy (TEM) to image a structure ranging from millimetres to Ångströms has made it an indispensable component of the toolkit of modern chemists. TEM has enabled unprecedented understanding of the atomic structures of materials and how structure relates to properties and functions. Recent developments in TEM have advanced the technique beyond static material characterization to probing structural evolution on the nanoscale in real time. Accompanying advances in data collection have pushed the temporal resolution into the microsecond regime with the use of direct-electron detectors and down to the femtosecond regime with pump-probe microscopy. Consequently, studies have deftly applied TEM for understanding nanoscale dynamics, often in operando. In this Review, time-resolved in situ TEM techniques and their applications for probing chemical and physical processes are discussed, along with emerging directions in the TEM field.

Light-Induced In Situ Transmission Electron Microscopy─Development, Challenges, and Perspectives

Transmission electron microscopy is a basic technique used for examining matter at the highest magnification scale available. One of its most challenging branches is in situ microscopy, in which dynamic processes are observed in real time. Among the various stimuli, like strain, temperature, and magnetic or electric fields, the light-matter interaction is rarely observed. However, in recent years, a significant increase in the interest in this technique has been observed. Therefore, I present a summary and critical review of all the in situ experiments performed with light, various technical possibilities for bringing radiation inside the transmission electron microscope, and the most important differences between the effects of light and electrons on the studied matter. Finally, I summarize the most promising directions for further research using light excitation.

Development of in situ optical-electrical MEMS platform for semiconductor characterization

In situ transmission electron microscopy (TEM) technology has become one of the fastest growing areas in TEM research in recent years. This technique allows researchers to investigate the dynamic response of materials to external stimuli inside the microscope. Optoelectronic functional semiconducting materials play an irreplaceable role in several key fields such as clean energy, communications, and pollution disposal. The ability to observe the dynamic behavior of these materials under real working conditions using advanced TEM technologies would provide an in-depth understanding of their working mechanisms, enabling further improvement of their properties. In this work, we designed a microelectromechanical-system-chip-based system to illuminate a sample inside a transmission electron microscope. This system allows simultaneous in situ optical and electrical measurements, which are crucial for optoelectronic semiconductor characterization.

Optical and Optoelectronic Property Analysis of Nanomaterials inside Transmission Electron Microscope

In situ transmission electron microscopy (TEM) allows one to investigate nanostructures at high spatial resolution in response to external stimuli, such as heat, electrical current, mechanical force and light. This review exclusively focuses on the optical, optoelectronic and photocatalytic studies inside TEM. With the development of TEMs and specialized TEM holders that include in situ illumination and light collection optics, it is possible to perform optical spectroscopies and diverse optoelectronic experiments inside TEM with simultaneous high resolution imaging of nanostructures. Optical TEM holders combining the capability of a scanning tunneling microscopy probe have enabled nanomaterial bending/stretching and electrical measurements in tandem with illumination. Hence, deep insights into the optoelectronic property versus true structure and its dynamics could be established at the nanometer-range precision thus evaluating the suitability of a nanostructure for advanced light driven technologies. This report highlights systems for in situ illumination of TEM samples and recent research work based on the relevant methods, including nanomaterial cathodoluminescence, photoluminescence, photocatalysis, photodeposition, photoconductivity and piezophototronics.

Multifunctional TEM-specimen holder equipped with a piezodriving probe and an electron irradiation port

The charging effect due to electron irradiation in an electron microscope has been studied so far with incident electrons. Here we report on a new specimen holder to control the charging effect by using electrons emitted from an irradiation port in the holder while maintaining a constant intensity of the incident electron beam. Details of the charging effect, such as electric field variation, are expected to be investigated by electron holography. The new specimen holder was developed by modifying a double-probe piezodriving specimen holder to introduce an electron irradiation port in one of its two arms. As a result, the new modified specimen holder consists of a piezodriving probe and an electron irradiation port, both of which can be controlled in three dimensions, using piezoelectric elements and micrometers. We demonstrate that variations in the charging effect for epoxy resin and surface contamination can be observed by electron holography.

System for in situ UV-visible illumination of environmental transmission electron microscopy samples

A system for illuminating a sample in situ with visible and ultraviolet light inside a transmission electron microscope was devised to study photocatalysts. There are many mechanical and optical factors that must be considered when designing and building such a system. Some of the restrictions posed by the electron microscope column are significant, and care must be taken not to degrade the microscope's electron-optical performance or to unduly restrict the other capabilities of the microscope. We discuss the nature of the design considerations, as well as the practical implementation and characterization of a solution. The system that has been added to an environmental transmission electron microscope includes a high brightness broadband light source with optical filters, a fiber to guide the light to the sample, and a mechanism for precisely aligning the fiber tip.

In situ transmission electron microscopy of light-induced photocatalytic reactions

Transmission electron microscopy (TEM) makes it possible to obtain insight into the structure, composition and reactivity of photocatalysts, which are of fundamental interest for sustainable energy research. Such insight can be used for further material optimization. Here, we combine conventional TEM analysis of photocatalysts with environmental TEM (ETEM) and photoactivation using light. Two novel types of TEM specimen holder that enable in situ illumination are developed to study light-induced phenomena in photoactive materials, systems and photocatalysts at the nanoscale under working conditions. The technological development of the holders is described and two representative photo-induced phenomena are studied: the photodegradation of Cu₂O and the photodeposition of Pt onto a GaN:ZnO photocatalyst.