Confirmation of the Dominant Defect Mechanism in Amorphous In–Zn–O Through the Application of <i>In Situ</i> Brouwer Analysis

Moffitt, Stephanie L.; Adler, Alexander U.; Gennett, Thomas; Ginley, David S.; Perkins, John D.; Mason, Thomas O.

doi:10.1111/jace.13518

Cited by 8 publications

(13 citation statements)

References 19 publications

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“…The maximum mobility trend of MO:x wt% PEI composites reflect the characteristics of the starting MO matrices, and thus it is expected that IGO should underperform the other MOs because of the strong affinity of Ga for oxygen. 52,53 However, note also that a mobility for IGO (In:Ga = 70:30, 300 °C) as high as ∼4.9 cm 2 /(V•s) is unprecedented. 51,54 Furthermore, while the V T values of In 2 O 3 :x wt% PEI monotonically increase (positive shift) with the PEI concentration (−14.6 ± 1.1 V for 0.0 wt% PEI, −3.9 ± 2.1 V for 1.0 wt% PEI, 12.3 ± 0.8 V for 6.0 wt% PEI), for all of other MO:x wt% PEI devices, V T first decreases (Figure 1d) from +12.5 ± 2.3 V (neat IZO), + 48.6 ± 7.9 V (neat IGO), and +11.3 ± 1.1 V (neat IGZO), to +5.8 ± 1.6 V (0.5 wt% PEIdoped IZO), + 18.7 ± 1.1 V (1.0 wt% PEI-doped IGO), and +8.5 ± 1.2 V (0.5 wt% PEI-doped IGZO), respectively, and then increases to much larger values of +44.0 ± 5.4 V (6.0 wt% PEI-doped IZO), + 28.2 ± 6.1 V (6.0 wt% PEI-doped IGO), and +24.0 ± 5.5 V (6.0 wt% PEI-doped IGZO), respectively.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Metal Composition and Polyethylenimine Doping Capacity Effects on Semiconducting Metal Oxide–Polymer Blend Charge Transport

et al. 2018

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Charge transport and film microstructure evolution are investigated in a series of polyethylenimine (PEI)-doped (0.0-6.0 wt%) amorphous metal oxide (MO) semiconductor thin film blends. Here, PEI doping generality is broadened from binary InO to ternary (e.g., In+Zn in IZO, In+Ga in IGO) and quaternary (e.g., In+Zn+Ga in IGZO) systems, demonstrating the universality of this approach for polymer electron doping of MO matrices. Systematic comparison of the effects of various metal ions on the electronic transport and film microstructure of these blends are investigated by combined thin-film transistor (TFT) response, AFM, XPS, XRD, X-ray reflectivity, and cross-sectional TEM. Morphological analysis reveals that layered MO film microstructures predominate in PEI-InO, but become less distinct in IGO and are not detectable in IZO and IGZO. TFT charge transport measurements indicate a general coincidence of a peak in carrier mobility (μ) and overall TFT performance at optimal PEI doping concentrations. Optimal PEI loadings that yield μ values depend not only on the MO elemental composition but also, equally important, on the metal atomic ratios. By investigating the relationship between the MO energy levels and PEI doping by UPS, it is concluded that the efficiency of PEI electron-donation is highly dependent on the metal oxide matrix work function in cases where film morphology is optimal, as in the IGO compositions. The results of this investigation demonstrate the broad generality and efficacy of PEI electron doping applied to electronically functional metal oxide systems and that the resulting film microstructure, morphology, and energy level modifications are all vital to understanding charge transport in these amorphous oxide blends.

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Section: ■ Experimental Sectionmentioning

confidence: 99%

Metal Composition and Polyethylenimine Doping Capacity Effects on Semiconducting Metal Oxide–Polymer Blend Charge Transport

et al. 2018

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“…For instance, the measurement of the electrical conductivity as a function of oxygen partial pressure (i.e., Brower analysis) is expected to follow the behavior of the majority charge carrier (electrons or holes), which can then be used to fit a proper defect chemistry model to obtain the equilibrium constants. [20,21] The major drawback of the Brower conductivity method is that the charge carrier mobility may also vary with the oxygen partial pressure, giving rise to a nontrivial interdependence difficult to untangle. Another common method for getting insights into the oxygen nonstoichiometry of thin films is measuring the lattice parameters by X-ray diffraction (XRD), since a unit-cell expansion is commonly observed in oxygen deficient oxides.…”

Section: Introductionmentioning

confidence: 99%

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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“…Becker implemented an in situ optical absorption relaxation approach similar to that to T. Beiger et al. 181 and surface exchange coefficients 5,48,50,64,66 over a wide range of temperatures and oxygen partial pressures. They also noted a discrepancy of the surface exchange coefficient, k chem ,…”

Section: Development Of In Situ Optical Absorbance Techniquementioning

confidence: 99%

In Situ Optical Absorption Studies of Point Defect Kinetics and Thermodynamics in Oxide Thin Films

Buckner

Perry

2019

Adv Materials Inter

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The authors review the use of in situ optical absorption to probe point defect equilibria and kinetics in oxides, with particular attention to thin films and high temperature measurements evaluating changes in oxygen content. The introduction notes the impact of point defects on oxide behavior, including differences in thin films vs. bulk materials, and describes methods to evaluate point defect equilibria and kinetics; advantages of optical absorption among these methods are highlighted. Section 2 provides an overview of how optical absorption and point defect concentrations are related, including various possible structural and electronic origins of defect-mediated absorption changes corresponding to oxygen content changes. Section 3 traces the development of historical understanding of optical absorption in nonstoichiometric oxides and emergence of thin film applications and measurement approaches that resulted. Section 4 details the procedure for determining surface exchange coefficients from optical transmission relaxation measurements and provides specific examples of how this approach uniquely has enabled new insights into thin film surface exchange behavior with and without current collectors. Section 5 provides examples of optically-derived diffusivity measurements and comparisons of bulk and thin This article is protected by copyright. All rights reserved. 2 film defect equilibria. Section 6 outlines potential opportunities and future developments in this area, and Section 7 concludes the manuscript.

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Confirmation of the Dominant Defect Mechanism in Amorphous In–Zn–O Through the Application of In Situ Brouwer Analysis

Cited by 8 publications

References 19 publications

Metal Composition and Polyethylenimine Doping Capacity Effects on Semiconducting Metal Oxide–Polymer Blend Charge Transport

Metal Composition and Polyethylenimine Doping Capacity Effects on Semiconducting Metal Oxide–Polymer Blend Charge Transport

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

In Situ Optical Absorption Studies of Point Defect Kinetics and Thermodynamics in Oxide Thin Films

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