Stable Correlated 4d² SrMoO₃ Films Epitaxially Coated on Al₂O₃ for Electromagnetic Shielding and Transparent Conductors

Abstract

A newly proposed design principle states that high transmittance of correlated TCs in the infrared and ultraviolet spectra can arise from correlationmediated intraband absorption between partially occupied transition metal d orbitals and the high transition energy from the O-2p to the d orbitals, respectively. Using this principle, we recently suggested 3d 1 SrVO 3 , 4d 1 SrNbO 3 , and 4d 2 SrMoO 3 perovskites as promising correlated TCs. [16] The electrical properties of correlated TC films can be particularly sensitive to crystallinity. Considering that the spatially directional d orbitals define the conduction band, [17−19] poor crystallinity often leads to dramatically reduced carrier mobility. Therefore, perovskite substrates including (LaAlO 3 ) 0.3 (Sr 2 TaAlO 6 ) 0.7 (LSAT) (lattice parameter: 3.88 Å), SrTiO 3 (3.905 Å), and GdScO 3 (3.97 Å in pseudo-cubic notation) have been used to grow single-crystalline SrVO 3 (3.84 Å), SrMoO 3 (3.97 Å), and SrNbO 3 (4.02 Å) films. The similarity in lattice parameters and atomic arrangements of the perovskite substrates have enabled epitaxial growth of correlated perovskite TCs. [3−13,16−19] However, only a few studies have attempted to characterize the transparent conducting properties of correlated perovskite films grown on Al 2 O 3 (a = b = 4.76 Å, c = 12.99 Å, γ = 120°). Importantly, Al 2 O 3 is the most commonly used substrate for optoelectronics. Its large bandgap (≈8.8 eV for corundum Al 2 O 3 ) [20] guarantees higher transmittance (greater than approximately 85% at 200−6000 nm) in a wider spectrum range than the range of SrTiO 3 (approximately 3.2 eV or 75% at 390−5000 nm). Notably, the transparency range of Al 2 O 3 is even wider than 200−2000 nm of silica glass. [21] Al 2 O 3 also has a low price and availability as a large-scale single crystal wafer, which makes it a superior alternative to perovskite substrates. The excellent thermal, chemical, and mechanical stability of Al 2 O 3 is suitable for applications in extreme environments. [22] Therefore, it is highly desirable to characterize the TC performance of correlated perovskite TC films coated on Al 2 O 3 .In this study, we investigated the transparent, conducting, and electromagnetic shielding properties of SrMoO 3 epitaxial films grown on (1102)-oriented Al 2 O 3 . By comparing the properties of SrMoO 3 with the properties of single-crystalline (sc) correlated TC films epitaxially grown on perovskite substrates, we observed that the correlated SrMoO 3 film on a Al 2 O 3 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 SrMoO 3 epitaxial films grown on Al 2 O 3 , the most commonly used substrate for optoelectronics, are investigated. The 45−80-nm-thick SrMoO 3 epitaxial films on ( ( ) ) 1 102 -oriented Al 2 O 3 exhibit low sheet resistance (< 50 Ω □ −1 ) at roo...

La-doped BaSnO3 for electromagnetic shielding transparent conductors

“…d The thus shows superior conductivity, transmittance, and SE than the potential TC-EMS materials Sn-doped In 2 O 3 (ITO) [ 10 ] and SrMoO 3 . [ 12 ] …”

“…The conductivity, carrier mobility, and density of were comparable to reports in single crystals, , and (Additional file 1 : Figure S2, Table S1 for comparison of conductivity, carrier mobility, and density among the reports of BLSO), indicating that BLSO films could showcase excellent conducting properties even on the industrially practical MgAl 2 O 4 substrate with assistance of MgO template layer. It should be noted that the sheet resistance of was smaller than 18–97 Ω ▯ –1 on 40–360-nm-thick Sn-doped In 2 O 3 films [ 10 ] and 10–38 Ω ▯ –1 on 45–80-nm-thick SrMoO 3 films [ 12 ]. The availability of highly conducting motivated us to measure the transmittance, and X-band SE thereof to evaluate the possibility of use for TC-EMS.…”

“…The oscillating transmittance in the visible region was likely attributable to interference between light reflected from the film and the substrate for 440-nm-thick BLSO films [ 33 ]. The visible transmittance of BLSO was higher than ~ 80% of 40–360-nm-thick Sn-doped In 2 O 3 films [ 10 ] and ~ 60% of 45–80-nm-thick SrMoO 3 films [ 12 ]. In these contexts, was superior to , whose transmittance was ~ 70% in the visible and abruptly decreased below ~ 400 nm.…”

“…Interest in TC-EMS has skyrocketed for new applications working in extreme environments, including invisible circuits, smart windows, transparent solar cells, and protective window coatings. Such demands impose stringent requirements on new stable transparent materials with high electromagnetic shielding efficiency [ 10 – 12 ]. To achieve the ideal TC-EMS material, a low sheet resistance (< 200 Ω ▯ − 1 ), high electromagnetic shielding capability (> 20 dB at 10 GHz in the X-band), and high-level visible transmittance (> 50% at a wavelength of 550 nm) are required.…”

“…BLSO exhibits high electron mobility in single crystals (~ 250 cm 2 V –1 s –1 ) [ 13 , 15 ] and films (~ 100 cm 2 V –1 s − 1 ) [ 15 , 22 ] at room temperature; the straight O–Sn–O connectivity and large Sn 5 s orbital in the cubic perovskite structure creates a dispersive conduction band with a small effective mass. BLSO has been shown to be thermally stable in air above 530 °C [ 14 ], while SrMoO 3 films lose metallicity above 450 °C because of over-oxidization [ 12 ]. The films can be coated over wide areas using a simple one-step process.…”