In Situ Method Correlating Raman Vibrational Characteristics to Chemical Expansion via Oxygen Nonstoichiometry of Perovskite Thin Films

Sediva, Eva; Defferriere, Thomas; Perry, Nicola H.; Tuller, Harry L.; Rupp, Jennifer L. M.

doi:10.1002/adma.201902493

Cited by 37 publications

(42 citation statements)

References 51 publications

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“…If this cell is employed as an oxygen pump against the material, a wide range of oxygen partial pressures can be covered by simply applying a voltage bias. [23,27,42] In this work, Ag/YSZ/LSF electrochemical cells were fabricated and afterwards measured in a special setup with electrical probes and a heating stage designed for in situ/operando spectroscopic ellipsometry analysis (Figure 3a inset and Experimental Section). As depicted in the inset of Figure 3a, DC voltage bias (ΔV) was applied between the LSF layer and the silver counter electrode both in anodic (ΔV > 0) and cathodic (ΔV < 0) modes.…”

Section: In Situ Ellipsometry Measurements As a Function Of Temperatumentioning

confidence: 99%

“…Finally, it was recently shown that Raman spectroscopy can also be used for tracking the oxygen non-stoichiometry of SrTi 1−x Fe x O 3−δ thin films. [27] Taking into consideration the benefits and limitations of the previous methods, an in situ ellipsometry technique is proposed here for quantifying the defect chemistry of LSF with x = 0.2, 0.4 and 0.5 (LSF20, LSF40 and LSF50, respectively) thin films through the measurements of optical conductivity. Ellipsometry is an optical spectroscopic technique based on the measure of the variation of polarization of a light beam reflected on a thin film sample.…”

Section: Introductionmentioning

confidence: 99%

“…Finally, it was recently shown that Raman spectroscopy can also be used for tracking the oxygen non‐stoichiometry of SrTi 1− x Fe x O 3− δ thin films. [ 27 ]…”

Section: Introductionmentioning

confidence: 99%

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Pushing the Study of Point Defects in Thin Film Ferrites to Low Temperatures Using In Situ Ellipsometry

Tang

Chiabrera

Morata

et al. 2021

Adv Materials Inter

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point defects, imperfections, and higher dimensional extended defects are known to severely impact the overall functional properties. [3,4] As a matter of example, oxygen vacancies were shown to enhance oxygen conductivity in oxide-ion electrolytes [5] or to boost oxygen incorporation and catalytic activity in mixed ionic electronic conductors (MIECs) [6,7] while weakening electronic and magnetic order in ferromagnetic oxides. [8] Besides, the presence of heterogeneous and homogenous interfaces in thin films was shown to drastically impact defect concentrations in such layers, which gives rise to deviations from bulk defect chemistry and, eventually, to new and unexpected properties. [9-11] Therefore, the knowledge and quantification of the chemical reactions that dominate the defect concentration in oxide thin films (i.e., defect chemistry) is essential for understanding the material behavior and for engineering their properties. This is especially relevant at intermediate-to-low temperatures (below 500 °C), where a high electrochemical activity and the nanometric dimensions of the thin films allow the point defect equilibrium with the environment, [12] hampering the use of the high temperature defect chemistry model from the bulk counterpart. A paradigmatic example of the large effect of point defects on the functional properties of transitional metal oxides can be found in the La 1−x Sr x FeO 3−δ (LSF) model family. LSF compounds crystalize in a perovskite ABO 3 structure and find application in many renewable energy technologies, such as solid oxide fuel cells (SOFC), [13] or electrochemical and photoelectrochemical water splitting. [14,15] In LSF, the substitution of trivalent La by divalent Sr gives rise to the generation of electronic holes and/or oxygen vacancies for electronic compensation, depending on the electrochemical equilibrium with the oxygen partial pressure of the environment. Interestingly, both point defects were found to be strongly correlated to many functional properties of LSF. For instance, the increase of holes concentration was found responsible for a large modification of the electronic structure, [16] affecting not just the electronic and magnetic transport properties [17] but also the oxygen evolution properties in aqueous media. [15] Meanwhile, oxygen vacancies were shown to take part into the rate-limiting step of oxygen incorporation at high temperature. [18] For these reasons, the development of a reliable and flexible in situ method for tracking the point defects of LSF thin films on any substrate and environment is fundamental for tailoring their properties. Unveiling point defects concentration in transition metal oxide thin films is essential to understand and eventually control their functional properties, employed in an increasing number of applications and devices. Despite this unquestionable interest, there is a lack of available experimental techniques able to estimate the defect chemistry and equilibrium constants in such oxides at intermediate-to-low temperatures. In ...

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Section: In Situ Ellipsometry Measurements As a Function Of Temperatumentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Pushing the Study of Point Defects in Thin Film Ferrites to Low Temperatures Using In Situ Ellipsometry

Tang

Chiabrera

Morata

et al. 2021

Adv Materials Inter

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“…To clarify the changes of switching symmetry in terms of the lithiation degree, we used in‐operando Raman spectroscopy to probe the A 1g vibration as a “marker” for titanium‐oxygen vibration upon applied external bias, Figure a. This methodology allows to probe the occupancy of the Wyckoff 8a and 16c structural positions that indicate local changes of the electronic states, and thus indicate metal–insulator transition.…”

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confidence: 99%

Lithium‐Battery Anode Gains Additional Functionality for Neuromorphic Computing through Metal–Insulator Phase Separation

et al. 2020

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Specialized hardware for neural networks requires materials with tunable symmetry, retention, and speed at low power consumption. The study proposes lithium titanates, originally developed as Li‐ion battery anode materials, as promising candidates for memristive‐based neuromorphic computing hardware. By using ex‐ and in operando spectroscopy to monitor the lithium filling and emptying of structural positions during electrochemical measurements, the study also investigates the controlled formation of a metallic phase (Li7Ti5O12) percolating through an insulating medium (Li4Ti5O12) with no volume changes under voltage bias, thereby controlling the spatially averaged conductivity of the film device. A theoretical model to explain the observed hysteretic switching behavior based on electrochemical nonequilibrium thermodynamics is presented, in which the metal‐insulator transition results from electrically driven phase separation of Li4Ti5O12 and Li7Ti5O12. Ability of highly lithiated phase of Li7Ti5O12 for Deep Neural Network applications is reported, given the large retentions and symmetry, and opportunity for the low lithiated phase of Li4Ti5O12 toward Spiking Neural Network applications, due to the shorter retention and large resistance changes. The findings pave the way for lithium oxides to enable thin‐film memristive devices with adjustable symmetry and retention.

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“…[ 44 ] With the introduction of “guest” and postmodification, the wrinkling peaks of the imidazole ring gradually shifted to lower wavenumber, which was caused by the lattice expansion process. [ 45 ] The results of time‐resolved photoluminescence (TRPL) (Figure 3c; see also Table S2, Supporting Information) confirmed that TCPP‐Fe was encapsulated in the open cavities of ZIF‐67, which result in a longer carrier lifetime (from 19.78 to 21.28 ns). The average emission lifetime of photoexcited charge for HZ@TCPP‐Fe was 21.83 ns, which was longer than that of HZ@TCPP‐Fe/Cu (12.03 ns), suggesting that excited‐state TCPP‐Fe connected with Cu 2+ .…”

Section: Resultsmentioning

confidence: 83%

Encapsulation of Porphyrin‐Fe/Cu Complexes into Coordination Space for Enhanced Selective Oxidative Dehydrogenation of Aromatic Hydrazides

Zhang

Liu

et al. 2020

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In Situ Method Correlating Raman Vibrational Characteristics to Chemical Expansion via Oxygen Nonstoichiometry of Perovskite Thin Films

Cited by 37 publications

References 51 publications

Pushing the Study of Point Defects in Thin Film Ferrites to Low Temperatures Using In Situ Ellipsometry

Pushing the Study of Point Defects in Thin Film Ferrites to Low Temperatures Using In Situ Ellipsometry

Lithium‐Battery Anode Gains Additional Functionality for Neuromorphic Computing through Metal–Insulator Phase Separation

Encapsulation of Porphyrin‐Fe/Cu Complexes into Coordination Space for Enhanced Selective Oxidative Dehydrogenation of Aromatic Hydrazides

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