Real-time Characterization Technique Research Articles

Unraveling the Dynamic Properties of New-Age Energy Materials Chemistry Using Advanced In Situ Transmission Electron Microscopy.

The field of energy storage and conversion materials has witnessed transformative advancements owing to the integration of advanced in situ characterization techniques. Among them, numerous real-time characterization techniques, especially in situ transmission electron microscopy (TEM)/scanning TEM (STEM) have tremendously increased the atomic-level understanding of the minute transition states in energy materials during electrochemical processes. Advanced forms of in situ/operando TEM and STEM microscopic techniques also provide incredible insights into material phenomena at the finest scale and aid to monitor phase transformations and degradation mechanisms in lithium-ion batteries. Notably, the solid-electrolyte interface (SEI) is one the most significant factors that associated with the performance of rechargeable batteries. The SEI critically controls the electrochemical reactions occur at the electrode-electrolyte interface. Intricate chemical reactions in energy materials interfaces can be effectively monitored using temperature-sensitive in situ STEM techniques, deciphering the reaction mechanisms prevailing in the degradation pathways of energy materials with nano- to micrometer-scale spatial resolution. Further, the advent of cryogenic (Cryo)-TEM has enhanced these studies by preserving the native state of sensitive materials. Cryo-TEM also allows the observation of metastable phases and reaction intermediates that are otherwise challenging to capture. Along with these sophisticated techniques, Focused ion beam (FIB) induction has also been instrumental in preparing site-specific cross-sectional samples, facilitating the high-resolution analysis of interfaces and layers within energy devices. The holistic integration of these advanced characterization techniques provides a comprehensive understanding of the dynamic changes in energy materials. This review highlights the recent progress in employing state-of-the-art characterization techniques such as in situ TEM, STEM, Cryo-TEM, and FIB for detailed investigation into the structural and chemical dynamics of energy storage and conversion materials.

Changes in Electrical Capacitance of Cell Membrane Reflect Drug Partitioning-Induced Alterations in Lipid Bilayer

The plasma membrane is a lipid bilayer that establishes the outer boundary of a living cell. The composition of the lipid bilayer influences the membrane's biophysical properties, including fluidity, thickness, permeability, phase behavior, charge, elasticity, and formation of flat sheet or curved structures. Changes in the biophysical properties of the membrane can be occasioned when new entities, such as drug molecules, are partitioned in the bilayer. Therefore, assessing drugs for their effect on the biophysical properties of the lipid bilayer of a cell membrane is critical to understanding specific and non-specific drug action. Previously, we reported a non-invasive technique for real-time characterization of cellular dielectric properties, such as membrane capacitance and cytoplasmic conductivity. In this study, we discuss the potential application of the technique in assessing the biophysical properties of the cell membrane in response to interaction with amiodarone compared to aspirin/acetylsalicylic acid and glucose. Amiodarone is a potent drug used to treat cardiac arrhythmia, but it also exerts various non-specific effects. Compared to aspirin and glucose, we measured a rapid and higher magnitude increase in membrane capacitance on cells under amiodarone treatment. Increased membrane capacitance induced by aspirin and glucose quickly returned to baseline in 15 s, while amiodarone-induced increased capacitance sustained and decreased slowly, approaching baseline or another asymptotic limit in ~2.5 h. Because amiodarone has a strong lipid partitioning property, we reason that drug partitioning alters the lipid bilayer context and subsequently reduces bilayer thickness, leading to an increase in the electrical capacitance of the cell membrane. The presented microfluidic system promises a new approach to assess drug-membrane interactions and delineate specific and non-specific actions of the drug on cells.

Real-Time Alignment and Reorientation of Polymer Chains in Liquid Crystal Elastomers

Liquid crystal elastomers (LCEs) exhibit soft elasticity due to the alignment and reorientation of mesogens upon mechanical loading, which provides additional mechanisms to absorb and dissipate energy. This enhanced response makes LCEs potentially transformative materials for biomedical devices, tissue replacements, and protective equipment. However, there is a critical knowledge gap in understanding the highly rate-dependent dissipative behaviors of LCEs due to the lack of real-time characterization techniques that probe the microscale network structure and link it to the mechanical deformation of LCEs. In this work, we employ in situ optical measurements to evaluate the alignment and reorientation degree of mesogens in LCEs. The data are correlated to the quantitative physical analysis using polarized Fourier-transform infrared spectroscopy. The time scale of mesogen alignment is determined at different strain levels and loading rates. The mesogen reorientation kinetics is characterized to establish its relationship with the macroscale tensile strain, and compared to theoretical predictions. Overall, this work provides the first detailed study on the time-dependent evolution of mesogen alignment and reorientation in deformed LCEs. It also provides an effective and more accessible approach for other researchers to investigate the structural-property relationships of different types of polymers.

An advanced high energy-efficiency rechargeable aluminum-selenium battery

Aluminum-ion batteries (AIBs) are considered as a promising alternative to traditional rechargeable batteries due to their high theoretical capacity, low cost, and multivalent-ion/multi-electron transfer, but are hindered from commercialization by the lack of suitable cathode materials. Herein, an aluminum-selenium (Al-Se) battery that operates at room temperature with high energy efficiency is reported. This Al-Se battery exhibits high selenium utilization with a discharge capacity of 607 mAh g−1, a reduced overpotential, and high volumetric capacity for over 100 cycles. Furthermore, ex-situ spectroscopic and microscopic investigations of the Se cathodes indicated the existence of an aluminum selenide component as the discharge product. Additionally, in-situ transmission electron microscopy provided not only insights into understanding the Al-Se electrochemistry, but also a real-time characterization technique to evaluate the electrochemistry of AIBs in general.

In Situ Resonant Raman Spectroscopy to Monitor the Surface Functionalization of MoS2 and WSe2 for High-k Integration: A First-Principles Study.

Surface functionalization of the dangling-bond-free MoS2, WSe2, and other TMDs (transition metal dichalcogenides) is of large practical importance, for example, in providing nucleation sites for the subsequent high-k dielectric integration. Of the surface functionalization methods, the reversible O or N atom adsorption on top of the chalcogen atoms is most promising. However, hazards such as severe oxidation or nitridation persist when the adsorption coverage is high. An in situ characterization technique, which can be integrated with the surface functionalization and dielectric deposition chamber, becomes valuable to enable the real-time monitoring of surface adsorption conditions. Raman spectroscopy, as a nondestructive characterization method without vacuum requirement, is a strong candidate. By utilizing first-principles calculations, Raman spectra of single-layer MoS2 and WSe2 with various O/N adsorption coverages are studied. The calculations suggest that the low-coverage O/N adsorbates will act as perturbations to the periodic lattice and activate the acoustic-phonon Raman scatterings. While high-coverage adsorptions will further activate and intensify the optical-phonon Raman scatterings of previously silent A2u and E1g modes, due to the breaking of reflection symmetry in the z direction, new phonon modes associated with the adatom oscillations are also introduced. All these pieces of evidence, together with the peak shifts of previously active A1g and E2g1 modes, suggest that in situ resonant Raman spectroscopy is capable of providing important information to quantify the O/N adsorption coverage and can be used as a valuable real-time characterization technique to monitor and control the surface functionalization conditions of MoS2 and WSe2.

Realtime Observation of Diffusing Elements in a Chemical Garden.

The chemical garden, which has been known as the plant-growth-like diffusion of chemicals since the 17th century, has regained much attention in recent years. Significant progress in research not only promoted the understanding of the phenomenon itself but also suggested a prospective method of synthesizing new materials via the chemical garden route. It is extremely important to introduce new characterization techniques to provide more insights into chemical diffusion and element redistribution during the reaction process. The present article describes some successful applications of the realtime X-ray fluorescence (XRF) movie technique to observe each diffusing element. The protagonist of the movie is a chemical garden reaction growing from a seed of calcium salt and ferrous salt mixtures. Through observation by an XRF movie, it has been found that the growth rate and diffusion behavior of calcium and iron are very different. This results in a macroscopic diversity of the element composition in the finally precipitated chemical garden structures. The present research not only reconfirms the potential of fabricating gradient composites through the self-organized chemical garden approach but also demonstrates the attractive achievements of XRF movies. It has been demonstrated that the XRF movie is an indispensable realtime characterization technique for the study of chemical garden reactions or even other related diffusions.

Transverse photothermal beam deflection technique for determining the transport properties of semiconductor thin films

Nonradiative transitions occurring in semiconductors result in thermal emissions carrying information on the material’s thermal and electronic properties. A simple one-dimensional theoretical model is devised which accounts for the photothermal signal variations due to nonradiative transitions occurring in semiconductor thinfilms. The theory was verified by determining the transport properties of p-type silicon wafer. We could get the thermal diffusivity, minority carrier lifetime, surface recombination velocity, and minority carrier mobility of CuInS2 thin films, thereby proving the efficiency and simplicity of photothermal beam deflection technique for real time characterization of semiconductor thin films. The film fabrication history, composition, and post deposition treatments play crucial role in determining the transport properties and the effect of these conditions on transport properties of the film as well as on the solar cell parameters is discussed.

In situ transient study of polymer film growth via simultaneous correlation of charge, mass, and ellipsometric measurements

Abstract Using three synchronized, in situ, nonintrusive, real-time characterization techniques to conduct transient observations, we revealed mechanistic details of a polymer film growth. A thin methylene green (MG) polymer coating (of the order of 35 nm) was used as a model system in this electrochemical microgravimetric imaging ellipsometry (EmIE) investigation. The direct correlation of changes in mass (via quartz crystal microbalance, QCM), ellipsometric angles (via imaging ellipsometry) with electrochemical conditions (in cyclic voltammetry, CV) provides discrete temporal and spatial information to help us decipher the underlying steps, from which we were able to separate adsorption, reduction, oxidation, desorption, and polymerization regimes involved in the deposition process. The evidence revealed in this study could have broad impact on the general understanding regarding how a film is deposited onto a metal surface.

Quantum-based atomisticsimulation of materials properties in transition metals

We present an overview of recent work on quantum-based atomisticsimulation of materials properties in transition metalsperformed in the Metals and Alloys Group at Lawrence LivermoreNational Laboratory. Central to much of this effort has beenthe development, from fundamental quantum mechanics, of robustmany-body interatomic potentials for bcc transition metals viamodel generalized pseudopotential theory (MGPT), providing closelinkage between ab initio electronic-structurecalculations and large-scale static and dynamic atomisticsimulations. In the case of tantalum (Ta), accurate MGPTpotentials have been so obtained that are applicable tostructural, thermodynamic, defect, and mechanical propertiesover wide ranges of pressure and temperature. Successfulapplication areas discussed include structural phase stability,equation of state, melting, rapid resolidification,high-pressure elastic moduli, ideal shear strength, vacancy andself-interstitial formation and migration, grain-boundary atomicstructure, and dislocation core structure and mobility. Anumber of the simulated properties allow detailed validation ofthe Ta potentials through comparisons with experiment and/orparallel electronic-structure calculations. Elastic anddislocation properties provide direct input intohigher-length-scale multiscale simulations of plasticity andstrength. Corresponding effort has also been initiated on themultiscale materials modelling of fracture and failure. Herelarge-scale atomistic simulations and novel real-time characterization techniques are being used to study voidnucleation, growth, interaction, and coalescence in series-endfcc transition metals. We have so investigated the microscopicmechanisms of void nucleation in polycrystalline copper (Cu),and void growth in single-crystal and polycrystalline Cu,undergoing triaxial expansion at a large, constant strain rate - aprocess central to the initial phase of dynamic fracture. The influence of pre-existing microstructure on the void growthhas been characterized both for nucleation and for growth, andthese processes are found to be in agreement with the generalfeatures of void distributions observed in experiment. We havealso examined some of the microscopic mechanisms of plasticityassociated with void growth.

Surface reaction kinetics of Ga 1− xIn xP growth during pulsed chemical beam epitaxy

The understanding of thin film growth processes and their control requires the development of surface-sensitive real-time optical characterization techniques that are able to provide insight into the surface reaction kinetics during an organometallic deposition process. These insights will allow us to move the control point closer to the point where the growth occurs, which in a chemical beam epitaxy (CBE) process is a surface reaction layer (SRL), built up of physisorbed and chemisorbed precursor fragments between the ambient and film interface. This contribution presents results on parameter estimations of rate constants and optical response factors in a reduced order surface kinetics (ROSK) model, which has been developed to describe the decomposition and growth kinetics of the involved organometallic precursors and their incorporation in the film deposition. As a real-time characterization technique, we applied p-polarized reflectance spectroscopy (PRS) during low temperature growth of epitaxial Ga 1− x In x P heterostructures on Si(0 0 1) substrates by pulsed chemical beam epitaxy (PCBE). The high surface sensitivity of PRS allows us to follow alterations in composition and thickness of the SRL as they are encountered during periodic precursor supply. The linkage of the PRS response to the ROSK model provides the base for the parameter estimation, giving insights into the organometallic precursor decomposition and growth kinetics.

Representation of GaP formation by a reduced order surface kinetics model using p-polarized reflectance measurements

This contribution presents results on the parameter estimation of rate constants and optical response factors in a reduced order surface kinetics (ROSK) model, which has been developed to describe the decomposition kinetics of the organometallic precursors involved and their incorporation into the film deposition. As a real-time characterization technique, we applied p-polarized reflectance spectroscopy (PRS) during low temperature growth of epitaxial GaP heterostructures on Si(001) substrates by pulsed chemical beam epitaxy. The high surface sensitivity of PRS allows us to follow alterations in the composition and thickness of the surface reaction layer as they are encountered during periodic precursor supply. Linkage of the PRS response to the ROSK model provides the base for the parameter estimation of the reduced order surface kinetics model, giving insights into the organometallic precursor decomposition and growth kinetics.

Studies of ferroelectric film growth processes using in situ, real-time ion beam analysis

Further technological advances in ferroelectric thin film-based devices requires to achieve a better understanding of the growth of ferroelectric and electrode layers, including oxygen incorporation during growth and other parameters. This can be achieved using in situ, real-time characterization techniques. We are currently using time-of-fligh ion scattering and recoil spectroscopy (TOF-ISARS) to study film growth processes. Results discussed in this review concerns initial studies of the growth of SrBi2Ta2O9 (SBT) films. As an example, the potential of TOF-ISARS has been demonstrated by determining that the layered SBT films are terminated in an incomplete (Bi2O2)2+ layer with an oxygen plane as the top most layer. This results and the implications for understanding the resistant to fatigue of Pt/SBT/Pt capacitors are discussed in this review.