Strongly correlated metals for transparent conductors

Transparent conductor (투명 전도체), strongly correlated metal (강상관 전자계 금속), wide transparency range(투과 영역), epitaxial thin film (에피 박막)Ⅰ. Introduction 1 Ⅱ. Strongly correlated transparent conductors 2 Ⅲ. Endurance against oxygen vacancies 3 3.1 Overview 3 3.2 Experimental details 5 3.3 Correlation-driven thickness reduction 11 3.4 Comparison with previous studies 14 3.5 Effect of oxygen vacancies on transparent conducting performance 15 3.6 Understanding the intriguing transparent conducting performance 15 3.7 Summary 17 Ⅳ. Unified design principle 18 4.1 Establishment of design principle 18 4.2 Experimental details 22 4.3 Performance of the transparent conductors 25 4.3.1 Enhanced transparency range 25 4.3.2 Electrical conducting properties 25 4.4 Application of design principle 28 4.4.1 Effect of correlated strength 28 4.4.2 Effect of p–d transition 30 4.5 Summary 33 Ⅴ. Lattice-orbital-charge coupled transparent conductors 34 5.1 Research Background 34 5.2 Experimental details 34 5.3 Transparent conducting performance 38 5.3.1 Enhanced infrared transparency 38 5.3.2 Metallic behavior 43 5.4 Ba substitution to induce the symmetry breaking of VO6 45 5.5 Reconstruction of V-t2g orbital 50 5.6 Modification of the electronic band structure 53 5.7 Summary 57 Ⅵ. Vertically aligned nanocomposite transparent conductors 58 6.1 Research background 58 6.2 Experimental details 60 6.3 Spontaneous phase separation 60 6.4 Super-broadband transparent conductors 66 6.4.1 Super-broadband transparency 66 6.4.2 Electrical conducting properties 66 6.5 Embedded Ba3V2O8 nanocolumns in the conducting SrVO3 films 69 6.6 Enabling epitaxial growth of our VAN-TCs 73 6.7 Growth mechanism of VAN-TCs 76 6.8 Summary 78 Ⅶ. Conclusion remarks 79 References 80 Summary (in Korean) 87DoctordCollectio

Stable Correlated 4d(2) SrMoO3 Films Epitaxially Coated on Al2O3 for Electromagnetic Shielding and Transparent Conductors

Correlated perovskites have attracted significant attention worldwide for their potential application in transparent conductors. However, most studies in this area have focused on single-crystalline films grown on expensive perovskites. In this study, the transparent conducting properties of SrMoO3 epitaxial films grown on Al2O3, the most commonly used substrate for optoelectronics, are investigated. The 45−80-nm-thick SrMoO3 epitaxial films on (Formula presented.) -oriented Al2O3 exhibit low sheet resistance (< 50 Ω □−1) at room temperature and high ultraviolet-visible transmittances (> 60%), comparable with the values expected from single-crystalline films. The highly conductive properties induced by two electrons in the outermost 4d orbitals guarantee a high electromagnetic shielding effectiveness of approximately 28.5 dB at 10 GHz in the X-band. The SrMoO3 films are thermally stable below 450 °C in air and 700 °C in vacuum. Taken together, these results indicate that SrMoO3 epitaxial films grown on (Formula presented.) Al2O3 can be highly promising for optoelectronic applications in extreme environments. © 2022 Wiley-VCH GmbH.FALS

Strong conductivity enhancement of La-doped BaSnO3 transparent films on Al2O3 with the assistance of templated epitaxy for electromagnetic shielding in extreme environments

Transparent La-doped BaSnO3 (BLSO) epitaxial films grown on expensive perovskites show promising conductive properties. However, BLSO films on Al2O3 have a higher sheet resistance by two orders of magnitude. In this research, the sheet resistance of BLSO films is recovered to that of the single-crystalline level by growing (111)-oriented BLSO epitaxial films on (0001)Al2O3 with the assistance of (111)BaZrO3/MgO template bilayer. Their intriguing transparent conductive properties, including high electromagnetic shielding effectiveness (~ 13.2 dB at 10 GHz) and high stability at 700 °C, will promote stable optoelectronic applications in extreme environments with economic benefits. Graphical Abstract: [Figure not available: see fulltext.]. © 2023, The Author(s).TRU

Oxygen-vacancy-endurable conductors with enhanced transparency using correlated 4d2 SrMoO3 Thin Films

Degenerately doped wide-bandgap semiconductors, e.g., Sn-doped In2O3, are the most conventional transparent conductors (TCs), but degradation of the TC performance by a doping bottleneck or instability due to oxygen vacancies is encountered. Recently, nondoped correlated metals have attracted great attention as a new strategy for developing next-generation TCs. To date, most studies of this brand-new type of TC have been biased toward 3d1 vanadates. Here, compared with 3d1 SrVO3, it is found that the 4d2 SrMoO3 thin films show promising TC properties: higher ultraviolet–visible transmittance of 80% and extremely low resistivity of 100 µΩ cm at room temperature. This enhancement in the SrMoO3 is ascribed to a p-4d transition occurring at higher photon energy and a higher number of electrons in the outermost 4d orbitals, respectively. In addition, the TC properties of the correlated SrMoO3 are resistive to oxygen vacancies. Using spectroscopic ellipsometry, it is found that this robustness is attributed to the lack of formation of defect states near the Fermi level, which is different from the observation in conventional TCs. Taken together, the correlated 4d2 SrMoO3 is appealing for next-generation oxygen-vacancy-endurable conductors with enhanced transparency. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim1

Hydrogen control of double exchange interaction in La0.67Sr0.33MnO3 for ionic-electric-magnetic coupled applications

The dynamic tuning of ion concentrations has attracted significant attention for creating versatile functionalities of materials, which are impossible to reach using classical control knobs. Despite these merits, the following fundamental questions remain: how do ions affect the electronic bandstructure, and how do ions simultaneously change the electrical and magnetic properties? Here, by annealing platinum-dotted La0.67Sr0.33MnO3 films in hydrogen and argon at a lower temperature of 200 °C for several minutes, a reversible change in resistivity is achieved by three orders of magnitude with tailored ferromagnetic magnetization. The transition occurs through the tuning of the double exchange interaction, ascribed to an electron-doping-induced and/or a lattice-expansion-induced modulation, along with an increase in the hydrogen concentration. High reproducibility, long-term stability, and multilevel linearity are appealing for ionic–electric–magnetic coupled applications. © 2021 Wiley-VCH GmbH1

Design Principles for the Enhanced Transparency Range of Correlated Transparent Conductors

Correlated transparent conductors (TCs) have attracted great attention because they can overcome the limitations of conventional TCs owing to their high visible transmittance and low sheet resistance. However, the most widely studied TC 3d1 SrVO3 exhibits low ultraviolet transmittance, and the recently investigated TC 4d2 SrMoO3 has low infrared transmittance. Here, it is proposed that the wide transparency range of correlated TCs arises from both high correlation strength and high transition energy from the O-2p to the transition metal d orbitals. Applying this comprehensive design principle to single-crystalline correlated metals, it is confirmed that correlated 4d1 SrNbO3 exhibits enhanced ultraviolet–visible–infrared transmittance, with low sheet resistance at room temperature, compared to 3d1 SrVO3 and 4d2 SrMoO3. Spectroscopic ellipsometry, X-ray photoelectron spectroscopy, and density functional theory calculations reveal that the advantageous properties of 4d1 SrNbO3 can be attributed to high p–d transition energy and moderate correlation effect. The design principle can aid the discovery of additional high-performance TC materials and further development of correlated TCs. © 2021 Wiley-VCH GmbH1

Vertically aligned nanocomposite films by self-assembled epitaxial nucleation for super-broadband transparent conductors

Designing super-broadband transparent conductors is challenging because of the exclusive nature of conductivity and infrared transmittance. Here, using a one-step process, we created vertically aligned nanocomposite conducting films with high transparency across a super-broad wavelength range. Vertically aligned transparent Ba3V2O8 nanocolumns with lateral ~100-nm widths enable high transmittance (>50%, even at a 4-μm wavelength) for all incident light and outperform that of Sn-doped In2O3, while the conducting SrVO3 matrix retains low resistivity (<0.56 mΩ cm at room temperature). A combined study of scanning transmission electron microscopy, scattering scanning near-field infrared microscopy, and X-ray diffraction revealed that spontaneous phase separation of Ba3V2O8 nanocolumns in a SrVO3 matrix film occurs via self-assembled epitaxial nucleation. Our vertically aligned nanocomposite films provide a fertile platform for next-generation optoelectronics. © 2022 The Authors. InfoMat published by UESTC and John Wiley & Sons Australia, Ltd.TRU

La-doped BaSnO3 for electromagnetic shielding transparent conductors

AbstractIn this work, we find that La-doped BaSnO3 (BLSO) is shown to be a promising electromagnetic shielding transparent conductor. While films grown on industrially practical optoelectronic MgAl2O4 substrates have higher sheet resistance by three orders of magnitude than in previous reports, we show how to recover the sheet resistance close to the single-crystal level by use of an MgO template layer which enables high quality (001)-oriented BLSO epitaxial film growth on (001) MgAl2O4. There is a positive correlation between crystallinity and conductivity; high crystallinity minimizes scattering of free electrons. By applying this design principle to 5–20% doped films, we find that highly crystalline 5% La-doped BLSO films exhibit low sheet resistance of ~ 8.7 Ω ▯ −1, high visible transmittance of ~ 80%, and high X-band electromagnetic shielding effectiveness of ~ 25.9 dB, thus outperforming transparent conducting oxides films of Sn-doped In2O3 and SrMoO3. Graphical Abstract</jats:p

BaZrO 3 /MgO-templated epitaxy showing a conductivity increase of three orders of magnitude for the Ba 0.95 La 0.05 SnO 3 films on Al 2 O 3 substrates, with very high transparency and X-band electromagnetic shielding

Acknowledgements: This work was supported by national R&D programs of the National Research Foundation of Korea funded by the Ministry of Science and ICT (project nos. NRF-2021M3F3A2A03015439, NRF-2021R1C1C1005042, and NRF-2018R1A5A1025511). We also acknowledge partial support from national R&D programs of the National Research Foundation of Korea funded by the Ministry of Education (project no. NRF-2021R1A6A3A13043948) and the DGIST R&D program of the Ministry of Science and ICT of Korea (project nos. 22-HRHR+-05, 22-CoE-NT-02, and 22-SENS-1). S.L. and J.L.M.-D. would like to thank Trinity College at Cambridge for partial support. J.L.M.-D. would like to thank the EU-H2020-ERC-ADG # 882929 grant, EROS, and the Royal Academy of Engineering CIET1819_24 for partial support.Transparent conductors with electromagnetic shielding capabilities (TC-EMS) are rare, despite their significant potential for creating new functionalities in energy and military applications. Here, we investigate the potential of La-doped BaSnO3 (BLSO) for TC-EMS since its epitaxial film has been known to have low sheet resistance and high visible transmittance. However, films grown on industrially practical Al2O3 substrates exhibit a sheet resistance three orders of magnitude higher than that of reported films grown on perovskites. Here, this problem is addressed by templating a BaZrO3/MgO bilayer on (0001)-oriented Al2O3 substrates to yield single-crystalline BLSO epitaxial films. The absence of grain boundaries in the epitaxial films minimizes the electron scattering. Due to the affirmative correlation between the conductivity and crystallinity, 5% La doping is optimal among the 5−20% La concentrations studied; these 480-nm-thick films have the highest crystallinity and the lowest sheet resistances of ~28 Ω ▯−1; this value is similar to that of single-crystalline levels. Due to their very high transmittances (~82% in a range 400−1000 nm) and effective X-band electromagnetic shielding (~18.6 dB), the BLSO epitaxial films grown on Al2O3 have great potential to be used for inexpensive TC-EMS applications

BaZrO3/MgO-templated epitaxy showing a conductivity increase of three orders of magnitude for the Ba0.95La0.05SnO3 films on Al2O3 substrates, with very high transparency and X-band electromagnetic shielding

Acknowledgements: This work was supported by national R&D programs of the National Research Foundation of Korea funded by the Ministry of Science and ICT (project nos. NRF-2021M3F3A2A03015439, NRF-2021R1C1C1005042, and NRF-2018R1A5A1025511). We also acknowledge partial support from national R&D programs of the National Research Foundation of Korea funded by the Ministry of Education (project no. NRF-2021R1A6A3A13043948) and the DGIST R&D program of the Ministry of Science and ICT of Korea (project nos. 22-HRHR+-05, 22-CoE-NT-02, and 22-SENS-1). S.L. and J.L.M.-D. would like to thank Trinity College at Cambridge for partial support. J.L.M.-D. would like to thank the EU-H2020-ERC-ADG # 882929 grant, EROS, and the Royal Academy of Engineering CIET1819_24 for partial support.AbstractTransparent conductors with electromagnetic shielding capabilities (TC-EMS) are rare, despite their significant potential for creating new functionalities in energy and military applications. Here, we investigate the potential of La-doped BaSnO3 (BLSO) for TC-EMS since its epitaxial film has been known to have low sheet resistance and high visible transmittance. However, films grown on industrially practical Al2O3 substrates exhibit a sheet resistance three orders of magnitude higher than that of reported films grown on perovskites. Here, this problem is addressed by templating a BaZrO3/MgO bilayer on (0001)-oriented Al2O3 substrates to yield single-crystalline BLSO epitaxial films. The absence of grain boundaries in the epitaxial films minimizes the electron scattering. Due to the affirmative correlation between the conductivity and crystallinity, 5% La doping is optimal among the 5−20% La concentrations studied; these 480-nm-thick films have the highest crystallinity and the lowest sheet resistances of ~28 Ω ▯−1; this value is similar to that of single-crystalline levels. Due to their very high transmittances (~82% in a range 400−1000 nm) and effective X-band electromagnetic shielding (~18.6 dB), the BLSO epitaxial films grown on Al2O3 have great potential to be used for inexpensive TC-EMS applications.</jats:p