Transmission Electron Microscopy Specimen Holder Research Articles

In Situ Transmission Electron Microscopy Study of Bubble Behavior Near the Surface of Ice Crystals by Using a Liquid Cell With a Peltier Cooling Holder.

Liquid cell transmission electron microscopy (LC-TEM) is a unique technique that permits in situ observations of various phenomena in liquids with high spatial and temporal resolutions. One difficulty with this technique is the control of the environmental conditions in the observation area. Control of the temperature ranging from room temperature to minus several tens of degrees Celsius, is desirable for controlling the supersaturation in various materials and for observing crystallization more easily. We have developed a cooling transmission electron microscopy specimen holder that uses Peltier devices, and we have combined it with a liquid cell to realize accurate temperature control in LC-TEM. We evaluated this system by using water as a specimen. Motionless bubbles, shown to be voids containing pressurized gas, formed in the specimen sometime after the temperature had reached -12°C. An electron diffraction pattern showed that the specimen turned into ice Ih after the formation of these bubbles, confirming that our system works properly and can induce crystallization. In addition, we analyzed the behavior of bubbles formed in the ice Ih, and we discussed the formation of these bubbles and their internal pressure.

Atomic-Level Observation of Electrochemical Platinum Dissolution and Redeposition.

An understanding of electrochemical dynamics at solid-liquid interfaces is essential to develop advanced batteries and fuel cells and so on. For example, an atomic-level understanding of electrochemical Pt dissolution and redeposition behavior is crucial for optimizing the material design and operating conditions of polymer electrolyte fuel cells (PEFCs). This understanding enables the prevention of the degradation of Pt nanoparticles used as electrocatalysts. However, the mechanisms of Pt dissolution and redeposition are still not fully understood due to the lack of spatial resolution available with current observation techniques. Here, we have revealed for the first time atomic-level electrochemical Pt dissolution and redeposition behavior using in-house-developed observation techniques. We achieved atomic-level observations of closed-cell type liquid electrochemical transmission electron microscopy (TEM) by combining in-house-developed microelectromechanical system (MEMS) chips as an electrochemical cell, an aberration-corrected TEM apparatus, and an energy filter. Furthermore, accurate and stable potential control was achieved using an in-house-developed reversible hydrogen electrode (RHE) with a liquid junction connected to the outside of a TEM specimen holder. Our observation results confirmed that Pt dissolves from surface step edges layer-by-layer, as previously predicted by the density functional theory (DFT). The observation techniques developed are also applicable to other research fields concerning electrochemistry.

Analysis of crystal defects by scanning transmission electron microscopy (STEM) in a modern scanning electron microscope

Dislocations and stacking faults are important crystal defects, because they strongly influence material properties. As of now, transmission electron microscopy (TEM) is the most frequently used technique to study the properties of single dislocations and stacking faults. Specifically, the Burgers vector b of dislocations or displacement vector R of stacking faults can be determined on the basis of the g·b = n (g·R = n) criterion by setting up different two-beam diffraction conditions with an imaging vector g. Based on the reciprocity theorem, scanning transmission electron microscopy (STEM) can also be applied for defect characterization, but has been less frequently used up to now. In this work, we demonstrate g·b = n (g·R = n) analyses of dislocations and stacking faults in GaN by STEM imaging in a scanning electron microscope. The instrument is equipped with a STEM detector, double-tilt TEM specimen holder, and a charge-coupled-device camera for the acquisition of on-axis diffraction patterns. The latter two accessories are mandatory to control the specimen orientation, which has not been possible before in a scanning electron microscope.

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.

Investigation of tribocharges and their migration in layered model toners by electron holography

The distribution of tribocharges in toner samples is studied by electron holography, a powerful tool for direct observations of the electric field. We carry out both in situ and ex situ observations on triboelectricity using model toner specimens, which are laminated with thin films, and a transmission electron microscopy specimen holder with two piezo-driving microprobes. We investigate specimens with stacking layer-patterns of “minus and weak minus” and “plus and minus.” The observed equipotential lines show a simple semi-ellipsoidal shape, regardless of the combination of toner films having different charging characteristics. Computer simulations for quantitative analyses of the electron hologram results with a modulated reference wave by a long-range electric field from the tribocharges are performed. Both the experimental results and the simulations indicate that the tribocharges are not localized at the positions where they are formed; rather they migrate to achieve a gradient charge density in the specimen. The charge quantity of the model toner is also evaluated by the simulation.

A MEMS Reactor for Atomic-Scale Microscopy of Nanomaterials Under Industrially Relevant Conditions

We present a microelectromechanical systems (MEMS) nanoreactor that enables high-resolution transmission electron microscopy (TEM) (HRTEM) of nanostructured materials with atomic-scale resolution during exposure to reactive gases at 1 atm of pressure. This pressure exceeds that of existing HRTEM systems by a factor of 100, thereby entering a pressure range that is relevant to industrial purposes. The nanoreactor integrates a shallow flow channel (35 ?m high) with a microheater and with an array of electron transparent windows of silicon nitride. The windows are only 10 nm thick but are mechanically robust. The heater has the geometry of a microhotplate and is made of Pt embedded in a silicon nitride membrane. To interface the nanoreactor, a dedicated TEM specimen holder has been developed. The performance is demonstrated by the live formation of Cu nanoparticles in a catalyst for the production of methanol. At 120 kPa and for temperatures of up to 500°C , the formation of these nanoparticles can be observed clearly and with an exceptionally low thermal drift. HRTEM images of the nanoparticles show atomic lattice fringes with spacings down to 0.18 nm.

In situ transmission electron microscopy study on Nb‐doped Pb(Zr0.95Ti0.05)O3 ceramics

The ferroelectric-to-ferroelectric phase transition between the high temperature (FE(RH)) and the low temperature (FE(RL)) rhombohedral phases in a Nb-doped Pb(Zr(0.95)Ti(0.05))O(3) ceramic was investigated with transmission electron microscopy (TEM). Both bright field images and electron diffraction patterns were monitored as a function of temperature as well as dc electric field. A special TEM specimen holder that permits the application of electric voltage up to 600 V was employed for the study of electric field-induced phase transition. It was found that both [1/2](011)(c)- and [1/2](111)(c)-type superlattice diffraction spots were present at room temperature when the specimen was under no electric field. The [1/2](111)(c)-type superlattice spots were observed to disappear during heating above the phase transition temperature. When dc electric fields were applied at room temperature, the [1/2](111)(c)-type superlattice spots vanished as the electric field-induced FE(RL) --> FE(RH) phase transition occurred.

In-situ observation of silver nanoparticle ink at high temperature

In-situ TEM (transmission electron microscopy) of silver nanoparticle ink at high temperature was carried out. Into a carbon film tube coating the spiral tungsten filament which was attached to the TEM specimen holder, a silver nanoparticle ink was injected. After evaporation, silver nanoparticles with an aggregated structure could be observed. The temperature of the tungsten wire can be controlled by DC current supplied by dry batteries. Fusion of smaller nanoparticles was observed at a higher temperature and some particles were incorporated to larger particles. This technique can be generally used to consider the sintering temperature of such metal nanoparticles.

MRT letter: Full‐tilt electron tomography with a piezo‐actuated rotary drive

Piezoelectric nanoactuation, which is rapidly becoming established as state-of-the-art positioning control in transmission electron microscopy (TEM), is extended here to include a rotational degree of freedom. A piezoelectric goniometer with both translational and rotary drive action has been designed with high level of miniaturization to fit into a standard TEM specimen holder shaft without compromising any of the performance of the default TEM goniometer and without any modifications to the TEM. Enhanced functionality of such a goniometer-in-goniometer is outlined and experimental results for electron tomography of nanostructures over a full tilt range of views, without any missing angles, are demonstrated.

Development of a stage-scanning system for high-resolution confocal STEM

A stage-scanning system is composed of a specially designed transmission electron microscopy specimen holder equipped with a piezo-driven specimen stage, power supplier and control software. This system enables the specimen to be scanned three-dimensionally, and therefore confocal scanning transmission electron microscopy (STEM) can be performed with a fixed electron-optics configuration. It is demonstrated that stage-scanning confocal STEM images can be obtained with the lateral atomic resolution and the specimen can be moved three-dimensionally with high precision.

Transmission electron microscopy specimen holder for simultaneous in situ heating and electrical resistance measurements

A transmission electron microscopy (TEM) specimen holder has been developed for the measurement of the electrical resistance of a TEM sample as a function of temperature. A custom TEM heating holder was modified for this purpose. Eight feedthrough wires were passed through the specimen holder; (i) providing current to the heater, (ii) allowing for the measurement of the hot stage temperature, and (iii) enabling the measurement of the electrical resistance of the sample. This configuration creates the opportunity to directly correlate changes in the resistance to microstructural changes as a function of temperature. The working of the holder is demonstrated by studies on a phase transformation in Al–Ge films. In this way, a direct correlation was found between changes in resistance and microstructure as a function of temperature.