Multi-Stimuli Operando Transmission Electron Microscopy for Two-Terminal Oxide-Based Devices.

The integration of microelectromechanical systems (MEMS)-based chips for in situ transmission electron microscopy (TEM) has emerged as a highly promising technique in the study of nanoelectronic devices within their operational parameters. This innovative approach facilitates the comprehensive exploration of electrical properties resulting from the simultaneous exposure of these devices to a diverse range of stimuli. However, the control of each individual stimulus within the confined environment of an electron microscope is challenging. In this study, we present novel findings on the effect of a multi-stimuli application on the electrical performance of TEM lamella devices. To approximate the leakage current measurements of macroscale electronic devices in TEM lamellae, we have developed a postfocused ion beam (FIB) healing technique. This technique combines dedicated MEMS-based chips and in situ TEM gas cells, enabling biasing experiments under environmental conditions. Notably, our observations reveal a reoxidation process that leads to a decrease in leakage current for SrTiO3-based memristors and BaSrTiO3-based tunable capacitor devices following ion and electron bombardment in oxygen-rich environments. These findings represent a significant step toward the realization of multi-stimuli TEM experiments on metal-insulator-metal devices, offering the potential for further exploration and a deeper understanding of their intricate behavior.

Controlled, reversible, and nondestructive generation of uniaxial extreme strains (>10%) in graphene.

Theoretical calculations have predicted that extreme strains (>10%) in graphene would result in novel applications. However, up to now the highest reported strain reached ∼1.3%. Here, we demonstrate uniaxial strains >10% by pulling graphene using a tensile-MEMS. To prevent it from slipping away it was locally clamped with epoxy using a femtopipette. The results were analyzed using Raman spectroscopy and optical tracking. Furthermore, analysis proved the process to be reversible and nondestructive for the graphene.

Weld-free mounting of lamellae for electrical biasing operando TEM.

Recent advances in microelectromechanical systems (MEMS)-based substrates and sample holders for in situ transmission electron microscopy (TEM) are currently enabling exciting new opportunities for the nanoscale investigation of materials and devices. The ability to perform electrical testing while simultaneously capturing the wide spectrum of signals detectable in a TEM, including structural, chemical, and even electronic contrast, represents a significant milestone in the realm of nanoelectronics. In situ studies hold particular promise for the development of Metal-Insulator-Metal (MIM) devices for use in next-generation computing. However, achieving successful device operation in the TEM typically necessitates meticulous sample preparation involving focused ion beam (FIB) systems. Conducting contamination introduced during the FIB thinning process and subsequent attachment of the sample onto a MEMS-based chip remains a formidable challenge. This article delineates an improved FIB-based sample preparation methodology that results in good electrical connectivity and operational functionality across various MIM devices. To exemplify the efficacy of the sample preparation technique, we demonstrate preparation of a clean cross section extracted from a Au/Pt/BaSrTiO3/SrMoO3 tunable capacitor (varactor). The FIB-prepared TEM lamella mounted on a MEMS-based chip showed current levels in the tens of picoamperes range at 0.1 V. Furthermore, the electric response and current density of the TEM lamella device closely align with macro-scale devices. These samples exhibit comparable current densities to their macro-sized counterparts thus validating the sample preparation process and confirming device connectivity. The simultaneous operation and TEM characterization of electronic devices enabled by this process enables direct correlation between device structure and function, which could prove pivotal in the development of new MIM systems.

Recent advances in in situ and operando characterization techniques for Li7La3Zr2O12-based solid-state lithium batteries.

Li7La3Zr2O12 (LLZO)-based solid-state Li batteries (SSLBs) have emerged as one of the most promising energy storage systems due to the potential advantages of solid-state electrolytes (SSEs), such as ionic conductivity, mechanical strength, chemical stability and electrochemical stability. However, there remain several scientific and technical obstacles that need to be tackled before they can be commercialised. The main issues include the degradation and deterioration of SSEs and electrode materials, ambiguity in the Li+ migration routes in SSEs, and interface compatibility between SSEs and electrodes during the charging and discharging processes. Using conventional ex situ characterization techniques to unravel the reasons that lead to these adverse results often requires disassembly of the battery after operation. The sample may be contaminated during the disassembly process, resulting in changes in the material properties within the battery. In contrast, in situ/operando characterization techniques can capture dynamic information during cycling, enabling real-time monitoring of batteries. Therefore, in this review, we briefly illustrate the key challenges currently faced by LLZO-based SSLBs, review recent efforts to study LLZO-based SSLBs using various in situ/operando microscopy and spectroscopy techniques, and elaborate on the capabilities and limitations of these in situ/operando techniques. This review paper not only presents the current challenges but also outlines future developmental prospects for the practical implementation of LLZO-based SSLBs. By identifying and addressing the remaining challenges, this review aims to enhance the comprehensive understanding of LLZO-based SSLBs. Additionally, in situ/operando characterization techniques are highlighted as a promising avenue for future research. The findings presented here can serve as a reference for battery research and provide valuable insights for the development of different types of solid-state batteries.

In situ electrochemistry inside a TEM with controlled mass transport.

The field of electrochemistry promises solutions for the future energy crisis and environmental deterioration by developing optimized batteries, fuel-cells and catalysts. Combined with in situ transmission electron microscopy (TEM), it can reveal functional and structural changes. A drawback of this relatively young field is lack of reproducibility in controlling the liquid environment while retaining the imaging and analytical capabilities. Here, a platform for in situ electrochemical studies inside a TEM with a pressure-driven flow is presented, with the capability to control the flow direction and to ensure the liquid will always pass through the region of interest. As a result, the system offers the opportunity to define the mass transport and control the electric potential, giving access to the full kinetics of the redox reaction. In order to show the benefits of the system, copper dendrites are electrodeposited and show reliable electric potential control. Next, their morphology is changed by tuning the mass transport conditions. Finally, at a liquid thickness of approximately 100 nm, the diffraction pattern revealed the 1,1,1 planes of the copper crystals, indicating an atomic resolution down to 2.15 Å. Such control of the liquid thickness enabled elemental mapping, allowing us to distinguish the spatial distribution of different elements in liquid.

Advanced microheater for in situ transmission electron microscopy; enabling unexplored analytical studies and extreme spatial stability.

In this work we present our advanced in situ heating sample carrier for transmission electron microscopy (TEM). The TEM is a powerful tool for materials characterization, especially when combined with micro electro-mechanical systems (MEMS). These deliver in situ stimuli such as heating, in which case temperatures up to 1300 °C can be reached with high temporal stability without affecting the original TEM spatial resolution: indeed, atomic resolution imaging can be routinely performed. Previously, the thermal expansion of suspended microheaters caused vertical displacement of the sample (bulging). As a result, changing temperatures required either continuous focus or stage adjustments, inducing resolution loss or mechanical drift, respectively. Moreover, those actions hinder the possibility to capture fast dynamic events. This new MEMS-based sample carrier, however, keeps the sample at constant z-position (no bulging) up to 700 °C. Furthermore, it enables energy dispersive x-ray spectroscopy (EDS) acquisition in the TEM up to an unmatched temperature of 1000 °C, with a drift rate down to 0.1 nm/min. Its viewable area of 850 µm2 features a temperature homogeneity up to 99.5%.