Design Principles for the Enhanced Transparency Range of Correlated Transparent Conductors

Abstract

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.

Infrared Transparent and Electromagnetic Shielding Correlated Metals via Lattice-Orbital-Charge Coupling

“…The schematic represents a super-broad-band transparent conductor (TC) with an electromagnetic shielding capability. (d) Compared with reported TCs, e.g., ITO, BLSO, VO 2 (B), V 6 O 13 , SrMoO 3 , and SrNbO 3 , Sr 1– x Ba x VO 3 is a potential material for super-broad-band TCs. The figures shown in (e) and (f) show the carrier density and mobility, respectively, as a function of the Ba concentration x .…”

“…Due to their high conductivity, Sr 1−x Ba x VO 3 films have a high electromagnetic shielding effectiveness of 22−31 dB at 10 GHz in the X-band (Figure 1c), which is dominantly attributed to absorption rather than reflection (Figures S5 and S6). As shown in Figure 1d, Sr 1−x Ba x VO 3 shows superior conductivity at room temperature and transmittance at a wavelength of 4 μm compared to those of ITO, BLSO, VO 2 (B), 15 V 6 O 13 , 15 SrNbO 3 , 17 and SrMoO 3 , 17 indicating its potential for application as a super-broad-band TC. In addition, the absorption-driven high electromagnetic shielding capability makes Sr 1−x Ba x VO 3 promising for stealth technology.…”

“…By using DFT, we obtain an effective mass of 3.06m band * for SrVO 3 , which is close to the value of 2.78m band * obtained in experimental reports. 12,17 DFT gives an effective mass of 3.13m band * for Sr 0.5 Ba 0.5 VO 3 . The larger effective mass of Sr 0.5 Ba 0.5 VO 3 indicates that the correlation effects between electrons in SrVO 3 increase with Ba substitution.…”

“…First, the large effective mass m * of correlated electrons shifts the screened plasma frequency, below which free electrons reflect light, toward the near-infrared range (0.7–1.4 μm) and shortens the electron mean free path (∼5 nm for SrVO 3 , cf. ∼ 50 nm for gold), guaranteeing higher transmittance over a broad wavelength spectrum ranging from the ultraviolet to near-infrared regions and metallic behavior even in ultrathin films. − Second, among correlated TCs, we selected SrVO 3 since its stronger correlation effect, inferred from the larger effective mass of 2.78 m band * for correlated electrons (1.75 m band * for SrNbO 3 , 1.19 m band * for SrMoO 3 ; m band * = mass of noninteracting electrons), will lead to higher sensitivity to small lattice changes than for SrMoO 3 and SrNbO 3 . Third, the properties of correlated TCs are known to depend on the size of the A-site atom in ABO 3 .…”

“…The electronic band structure of SrVO 3 includes an unoccupied e g band of V- d orbitals ( d x 2 ‑ y 2 , d z 2 ) above the Fermi level, a partially occupied t 2g band of V- d orbitals ( d xy , d yz , d zx ) near the Fermi level, and occupied O-2 p orbitals below the Fermi level. As schematically shown in Figure a, the correlation-driven on-site Coulomb repulsion further modifies the t 2g band near the Fermi level, forming a quasiparticle peak at the Fermi level and a Hubbard band at the band edges, ,, which differ from the strong density of states near the Fermi level in conventional metals. With a stronger correlation effect, the densities of the quasiparticle peak and Hubbard band decrease and increase, respectively.…”