Solution‐Processable Epitaxial Metallic Delafossite Oxide Films

Abstract

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.

Disorder-enhanced effective masses and deviations from Matthiessen's rule in PdCoO$_2$ thin films

“…Before the development of thin films, the high conductivity of single crystals restricted optical studies of PdCoO 2 using a reflection geometry [14]; however, this made studying the low-energy response extremely difficult as the reflectivity is nearly indistinguishable from a perfect mirror. The first development of thin films of PdCoO 2 via PLD by Harada et al has lead to subsequent work on thin film deposition [11,[16][17][18][19] which presents new opportunities to study intrinsic material properties with new experimental techniques [20]. With the development of high quality epitaxial thin films, optical measurements in the transmission geometry are now possible.…”

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

“…Such a c-axis orientation characteristic can be attributed to the low surface energy of the (00l) plane, as also observed in our previous studies on metallic Ag-, Pd-, and Pt-based delafossite thin films synthesized by the similar deposition method. [5,32] The full width of half-maximum was determined to be ≈0.80° for the rocking curve of (006) peak (Figure S2, Supporting Information). It is pity that the obtained CuRhO 2 thin film shows non-epitaxial characteristic on the sapphire, which can be ascribed to large lattice mismatch of +11.19% for the CuRhO 2 on Al 2 O 3 .…”

“…[62] Precursor Solution Preparation and Thin Film Fabrication: Stoichiometric copper nitrate trihydrate (Cu(NO 3 ) 2 •3H 2 O, 99.9%), rhodium nitrate solution (Rh(NO 3 ) 3 , 5%Rh in solution), and magnesium nitrate hexahydrate (Mg(NO 3 ) 2 •6H 2 O, 99.9%) were dissolved in the mixture solvent of nitric acid (65-68%) and 2-methoxyethanol (99.5%), similar to that of the previous report on metallic delafossite thin films. [5] The precursor solutions were stirred for more than 10 h at room-temperature to get bottle-green solutions. Single-crystal sapphire (Al 2 O 3 ) substrates were used to fabricate the CuRhO 2 related thin films.…”

“…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".…”

Determination of the phase coherence length of PdCoO2 nanostructures by conductance fluctuation analysis

“…As explored in semiconductor heterostructures in the last decades [2], the quantum interference effects have been intensively studied with mesoscopic devices fabricated by a well-regulated growth technique and high-resolution lithography techniques. As for PdCoO2, c-axis oriented thin films have been achieved by pulsed-laser deposition (PLD) [16,17], molecular beam epitaxy [18,19], and solid-phase reactions of precursors [20,21]. Establishing a route to pattern PdCoO2 thin films to submicron scales is essential for realizing quantum devices utilizing PdCoO2 thin films and heterostructures.…”