Large thermopower anisotropy in 
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 thin films

Yordanov, Petar; Sigle, Wilfried; Kaya, Pinar; Gruner, Markus E.; Keimer, B.; Habermeier, H.–U.

doi:10.1103/physrevmaterials.3.085403

Cited by 37 publications

(42 citation statements)

References 21 publications

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“…Recently, PdCoO 2 thin films have been successfully synthesized by molecular beam epitaxy (MBE) and pulsed laser deposition (PLD). [ 2,15–17 ] Specifically, Brahlek et al systematically investigated the growth of high‐quality epitaxial PdCoO 2 thin films (10 × 10 cm 2 ) by MBE, where the room temperature conductivity has reached as high as 2.6 × 10 5 S cm −1 for a 125 nm‐thick thin film annealed in oxygen. [ 17 ] It is suggested that metallic ABO 2 thin films can be potential utilized for various electronic devices ranging from low‐resistivity bottom electrodes for 2D materials to correlated transparent conductors.…”

Section: Introductionmentioning

confidence: 99%

“…[ 17 ] It is suggested that metallic ABO 2 thin films can be potential utilized for various electronic devices ranging from low‐resistivity bottom electrodes for 2D materials to correlated transparent conductors. [ 2,15–17 ] Moreover, as the isostructural compounds, PtCoO 2 has the lowest room temperature resistivity amongst the oxide system known, [ 1 ] and PdCrO 2 shows strong coupling between the antiferromagnetism and the conduction electrons. [ 18,19 ] Growing PtCoO 2 and PdCrO 2 thin films will expand the fundamental investigations and further potential applications of metallic delafossite oxides.…”

Section: Introductionmentioning

confidence: 99%

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Solution‐Processable Epitaxial Metallic Delafossite Oxide Films

Wei

Gong

Zhao

et al. 2020

Adv Funct Materials

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Metallic delafossites ABO2, as the new benchmark of ultra‐high conductive oxides, have recently attracted great interest. The harsh processing conditions and dimensional sizes obviously limit the fundamental sciences and technological applications. Here, a low‐cost and facile solution approach is realized to synthesize epitaxial metallic ABO2 thin films including PtCoO2, PdCoO2, and PdCrO2 with a dimension up to two‐inches in diameter, showing ultra‐high room temperature conductivity. The electrical properties, growth mechanisms, and potential technical applications including transparent conducting films and hydrogen evolution reaction activity are unveiled. The achievements of epitaxial metallic delafossites ABO2 thin films through solution methods will pave the route to producing wafer‐scaled ultra‐high conductive metallic delafossites.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Solution‐Processable Epitaxial Metallic Delafossite Oxide Films

Wei

Gong

Zhao

et al. 2020

Adv Funct Materials

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“…The intermixing-induced alloying of the Al and Cr atoms was found to play a crucial role in stabilizing the nucleation of CuCrO 2 delafossite phase and in reducing the most stable impurity phase Cr 2 O 3 often found in other delafossites. We believe a similar consideration can be also applied to Co-based delafossites as the formation of the Co 3 O 4 spinel structure has been also a challenge for, e.g., PdCoO 2 7 , 8 , 10 , 11 . Our results suggest that the key to achieving the layer-by-layer growth of CuCrO 2 delafossite films is the nucleation of the structurally similar CuCr 1−x Al x O 2 buffer layer at the interface when grown on structurally dissimilar substrates, e.g., conventional Al 2 O 3 substrates.…”

Section: Introductionmentioning

confidence: 99%

Interfacial stabilization for epitaxial CuCrO2 delafossites

Yoon

Lupini

et al. 2020

Sci Rep

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ABo 2 delafossites are fascinating materials that exhibit a wide range of physical properties, including giant Rashba spin splitting and anomalous Hall effects, because of their characteristic layered structures composed of noble metal A and strongly correlated Bo 2 sublayers. However, thin film synthesis is known to be extremely challenging owing to their low symmetry rhombohedral structures, which limit the selection of substrates for thin film epitaxy. Hexagonal lattices, such as those provided by Al 2 o 3 (0001) and (111) oriented cubic perovskites, are promising candidates for epitaxy of delafossites. However, the formation of twin domains and impurity phases is hard to suppress, and the nucleation and growth mechanisms thereon have not been studied for the growth of epitaxial delafossites. In this study, we report the epitaxial stabilization of a new interfacial phase formed during pulsed-laser epitaxy of (0001)-oriented CuCrO 2 epitaxial thin films on Al 2 o 3 substrates. Through a combined study using scanning transmission electron microscopy/electronenergy loss spectroscopy and density functional theory calculations, we report that the nucleation of a thermodynamically stable, atomically thick CuCr 1−x Al x o 2 interfacial layer is the critical element for the epitaxy of CuCrO 2 delafossites on Al 2 o 3 substrates. This finding provides key insights into the thermodynamic mechanism for the nucleation of intermixing-induced buffer layers that can be used for the growth of other noble-metal-based delafossites, which are known to be challenging due to the difficulty in initial nucleation. ABO 2 delafossite oxides have attracted considerable interest because of their fascinating properties that depend on the choice of A and B site elements 1-3. Metallic delafossites, especially PdCoO 2 and PdCrO 2 , exhibit very high conductivity on the order of 10-8 Ω cm with an extremely long mean free path of l m ~ 20 μm at low temperatures 4,5. While the high conductivity and the large spin-orbit coupling associated with huge Rashba splitting 6 make such metallic delafossites promising candidates for future spintronic devices, their synthesis in thin film forms has not been established. There have been several attempts to grow metallic delafossite thin films, and Pd-based delafossites were recently grown by pulsed laser epitaxy (PLE) 7-9 and molecular beam epitaxy (MBE) 10,11. The quality and performance of thin films, however, are not as good as those of single crystals, thus further improvements are needed. The major problem that needs to be overcome is the poor structural quality due to the formation of twin domains and impurity phases 7-11 , which mainly originate from the initial nucleation and structural dissimilarity between the film and substrate. To achieve high quality thin films, therefore, not only is an isostructural substrate or buffer layer with similar lattice parameters needed, but also a deeper understanding on the nucleation and growth mechanisms. Among various delafossite compounds, Cu-based delafossi...

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“…Delafossite-type oxide AMO 2 , in which A and M are mono valent and trivalent cation respectively, have been explored intensively as transparent conductors, photocatalysts, hole collection electrodes, and thermoelectrics due to their fascinating physical properties. [1][2][3][4][5][6][7][8] Hosono group in 1997 started the design of p-type transparent conducting (TC) oxides through "chemical discovered delafossite CuMO 2 thin films show low p-type conductivity arising from the deep level of acceptor defects. [21] Rh-based oxide with 4d 6 configuration in an octahedral crystal environment shows the potential to achieve a high p-type conductivity, because the electronic ground state is a low-spin (LS) state with filled d t 2g level which behaves similarly to a "quasi-closed shell configuration".…”

Section: Introductionmentioning

confidence: 99%

p‐Type Near‐Infrared Transparent Delafossite Thin Films with Ultrahigh Conductivity

Gong

Zheng

et al. 2022

Advanced Optical Materials

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modulation of the valence band" (CMVB), and the delafossite CuAlO 2 was got the nod as p-type TC thin films. [1] Subsequently, the Cu-based delafossite oxides (CuMO 2 , M = Cr, B, Ga, Sc, Y, etc.) are extensively studied in the field of p-type TC thin films. [9][10][11][12][13][14] In particular, the high optical transparency of CuMO 2 thin films in the near-infrared (NIR, 750 to 2400 nm) spectrum is potentially utilized in emerging NIR TC applications, such as solar cells, infrared imaging and emission devices, and fiber-optic communications operating at 1550 nm. [11,15,16] High conductivity p-type oxides are unavailable since the upper edge of valence band (VB) is composed of strongly localized oxygen 2p orbitals. [17][18][19] The design for mitigating the localization behavior is to extend the VB structure by introducing covalency in the metal-oxygen bonding, namely CMVB. [1] For delafossite CuMO 2 oxides, the cationic Cu + has a closed shell 3d 10 electron configuration, in which the energy level is almost close to the oxygen 2p levels. The tetrahedral coordination of oxide ions will prompt the outermost eight electrons coordinate with the cations. Therefore, more covalent bonds and hybridization levels between Cu 3d 10 and O 2p 6 are introduced, resulting in a large dispersion and reduction of the localization behavior for the VB. [20] However, previously Design and implementation of efficient p-type transparent conducting (TC) oxides with excellent performance are the global material challenge. The strategy of "chemical modulation of the valence band" triggers the enthusiasm for p-type TC delafossite CuMO 2 . However, the low conductivity of previous CuMO 2 films obstructs the development of delafossite-based electronics. Herein, a new p-type 4d transition metal Rh-based CuRhO 2 film with large-size is first designed and fabricated by a facile solution method. Roomtemperature conductivity as high as 735 S cm −1 is achieved by substituting 10%Mg in Rh sites. Additionally, the acceptor-doped CuRhO 2 films exhibit high near-infrared transmittance of 85-60% with low room-temperature sheet resistance of 4.28-0.18 kΩ sq −1 . Furthermore, the electronic structure, electrical transport mechanism, and intra-band excitation feature for the CuRhO 2 film are unveiled. The theoretical and experimental results make a great advance in p-type TC films and will pave a promising blueprint for future multifunctional opto-electronic devices.

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Large thermopower anisotropy in PdCoO2 thin films

Cited by 37 publications

References 21 publications

Solution‐Processable Epitaxial Metallic Delafossite Oxide Films

Solution‐Processable Epitaxial Metallic Delafossite Oxide Films

Interfacial stabilization for epitaxial CuCrO2 delafossites

p‐Type Near‐Infrared Transparent Delafossite Thin Films with Ultrahigh Conductivity

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