Unconventional aspects of electronic transport in delafossite oxides

Daou, Ramzy; Frésard, Raymond; Eyert, V.; Hébert, S.; Maignan, A.

doi:10.1080/14686996.2017.1393633

Cited by 59 publications

(39 citation statements)

References 112 publications

(232 reference statements)

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“…1(c), form a triangular lattice with an inter-oxygen distance of 2.83 Å that equals to the inplane lattice constants. This inter-oxygen distance in PdCoO 2 is close to that in Al 2 (0001) substrates (SHINKOSHA CO., LTD) were ultrasonically cleaned with acetone and ethanol, followed by annealing in air at 900 • C for 12 h to obtain an atomically flat surface with step-and-terrace structures. The annealed substrate was loaded into a vacuum chamber and preheated at T = 700 • C for 10 min under an oxygen partial pressure of PO 2 = 100 mTorr.…”

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confidence: 86%

“…As shown in Fig. 2(d), the HRTEM image of a PdCoO 2 thin film shows periodic bright lines stacked along the PdCoO 2 [0001] direction, corresponding to the layered crystal structure of the PdCoO 2 thin film. The period of the bright lines is about 0.59 nm, which agrees well with the 1/3 unit cell height, i.e., a single stack of the Pd layer and CoO 2 octahedron.…”

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confidence: 99%

“…We note that the Al 2 O 3 substrate showed normally forbidden (0003) and (0003) spots, which might be due to the strained crystal structure with off-stoichiometric oxygen composition 19 caused by annealing in the growth process. The periodic HRTEM image evidences that the atomic layers in PdCoO 2 are regularly ordered along the PdCoO 2 [0001] direction.…”

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Highly conductive PdCoO2 ultrathin films for transparent electrodes

2018

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We report on the successful synthesis of highly conductive PdCoO2 ultrathin films on Al2O3 (0001) by pulsed laser deposition. The thin films grow along the c-axis of the layered delafossite structure of PdCoO2, corresponding to the alternating stacking of conductive Pd layers and CoO2 octahedra. The thicknessdependent transport measurement reveals that each Pd layer has a homogeneous sheet conductance as high as 5.5 mS in the samples thicker than the critical thickness of 2.1 nm. Even at the critical thickness, high conductivity exceeding 10 4 Scm -1 is achieved. Optical transmittance spectra exhibit high optical transparency of PdCoO2 thin films particularly in the near-infrared region. The concomitant high values of electrical conductivity and optical transmittance make PdCoO2 ultrathin films as promising transparent electrodes for triangular-lattice-based materials.

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Highly conductive PdCoO2 ultrathin films for transparent electrodes

2018

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“…conductivity metals featuring broad conduction bands whose character is dominantly that of the A site cation Pd or Pt (4)(5)(6)(7)(8)(9), with the B-site Co 3+ cation in the band insulating and non-magnetic 3d 6 configuration.…”

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Probing spin correlations using angle-resolved photoemission in a coupled metallic/Mott insulator system

et al. 2020

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T.O.), Andy.Mackenzie@cpfs.mpg.de (A.P.M.), philip.king@st-andrews.ac.uk (P.D.C.K.) † These authors contributed equally to this work.Abstract: A nearly free electron metal and a Mott insulating state can be thought of as opposite ends of possibilities for the motion of electrons in a solid. In the magnetic oxide metal PdCrO 2 , these two coexist as alternating layers. Using angle resolved photoemission, we surprisingly find sharp band-like features in the one-electron removal spectral function of the correlated subsystem. We show that these arise because a hole created in the Mott layer moves to and propagates in the metallic layer while retaining memory of the Mott layer's magnetism. This picture is quantitatively supported by a strong coupling analysis capturing the physics of PdCrO 2 in terms of a Kondo lattice Hamiltonian. Our findings open new routes to use the non-magnetic probe of photoemission to gain insights into the spin-susceptibility of correlated electron systems.One Sentence Summary: An intrinsically non-magnetic spectroscopy is shown to have strong magnetic sensitivity in Kondo-coupled PdCrO 2 .Main Text: PdCrO 2 is a member of the broad class of layered triangular lattice materials whose layer stacking sequence (see Fig. 1A) is that of the delafossite structural family ABO 2 (1). In a simple ionic picture of the delafossites, triangular co-ordinated layers of A + ions are stacked between BO 2 octahedra in which the B ions also have triangular co-ordination (2, 3). Most delafossites are insulating or semiconducting. PdCoO 2 and PtCoO 2 , however, are extremely high

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“…PdO, PdO 2 , PtO, PtO 2 , PtO 3 , and not Pt 1+ as occours in Pt-containing delafossites.Oxide materials based on the ABO 2 delafossite structure are of particular interest due to the novel properties that accompany their cation variation at A and B sites. These properties are of interest to fundamental science [5,6,7,8,9] as well as applications [10]. Usually, the semiconductor delafossites consist of Ag or Cu at the A-site and several trivalent cations like Al, Fe or Ga at the B-site.…”

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Growth of CuFeO2 single crystals by the optical floating-zone technique

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et al. 2020

Journal of Crystal Growth

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CuFeO 2 single crystals up to 50 mm in length and up to 10 mm in diameter were grown by the optical floating-zone method. Stoichiometric polycrystalline rods with a diameter of 6-12 mm were used as feed materials to produce crystals of sufficient size to be used as substrates for the growth of thin films of delafossites.For stable growth along the c-axis, low growth rates of 0.4 mm/h are necessary.Due to the incongruent melting behavior of CuFeO 2 , a stable melt zone requires adjustment of the lamp power during growth. The melting of CuFeO 2 is not simply incongruent because the thermodynamic equilibrium includes more than two solid phases and the melt; the gas phase is also involved. The crystals were characterized by X-ray diffraction and X-ray fluorescence measurements. from Catherinebourgh, Sibiria" -which instead he reported in the year 1873 to be composed from equimolar quantities of Cu + 2 O with the combination of Fe 3+ 2 O 3 , about 3.5% Al 2 O 3 [1]. This chemical composition can be written as Cu(Fe,Al)O 2 . The new mineral was given the name delafossite. In the years since Friedel's discovery a large number of other A + B 3+ O 2 compounds have become known that show basically the same structural features: BO 6 octahedra form layers that are stacked parallel to (001), and these edge-sharing octahedral sheets are connected along the [001] direction by linear O -A + -O bonds. Depending on details of the stacking sequence, the structures are usually either hexagonal or trigonal [2]. As an exception, Cu + Mn 3+ O 2 is monoclinic with space group C2/m [3]. Shannon et al. [4] revealed that not only copper and silver can acts as the A + element, but also other quite noble metals like palladium or even platinum. This is surprising because oxides of the platinum group metals are not only scarce and often unstable, but also the known platinum group binary oxides show oxidation states of 2+ or higher, e.g. PdO, PdO 2 , PtO, PtO 2 , PtO 3 , and not Pt 1+ as occours in Pt-containing delafossites.Oxide materials based on the ABO 2 delafossite structure are of particular interest due to the novel properties that accompany their cation variation at A and B sites. These properties are of interest to fundamental science [5,6,7,8,9] as well as applications [10]. Usually, the semiconductor delafossites consist of Ag or Cu at the A-site and several trivalent cations like Al, Fe or Ga at the B-site. Important among the semiconducting delafossites is CuAlO 2 with its relatively high mobility for a p-type transparent conducting oxide [11]. Pd-and Pt-based compounds (for A + ) are metallic delafossite oxides where B-site cations are transition metals like Co, Cr or Rh [4,12,13]. Among these, the growth of single crystalline PdCoO 2 has become of interest due to its ultra-high conductivity at room temperature. Recently an in-plane resistivity ρ ab = 2.6 µΩ·cm at 295 K was measured for sub-mm-sized PdCoO 2 crystals, which makes this material the most conductive oxide known, comparable to the best metallic conductors Ag, Cu, Au a...

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Unconventional aspects of electronic transport in delafossite oxides

Cited by 59 publications

References 112 publications

Highly conductive PdCoO2 ultrathin films for transparent electrodes

Highly conductive PdCoO2 ultrathin films for transparent electrodes

Probing spin correlations using angle-resolved photoemission in a coupled metallic/Mott insulator system

Growth of CuFeO2 single crystals by the optical floating-zone technique

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