Abstract
The Pd- and Pt-based ABO2 delafossites are a unique class of layered, triangular oxides with two-dimensional electronic structure and a large conductivity that rivals the noble metals. Here, we report successful growth of the metallic delafossite PdCoO2 by molecular beam epitaxy (MBE). The key challenge is controlling the oxidation of Pd in the MBE environment where phase segregation is driven by the reduction of PdCoO2 to cobalt oxide and metallic palladium. This is overcome by combining low-temperature (300 °C) atomic layer-by-layer MBE growth in the presence of reactive atomic oxygen with a postgrowth high-temperature anneal. Thickness dependence (5-265 nm) reveals that in the thin regime (<75 nm), the resistivity scales inversely with thickness, likely dominated by surface scattering; for thicker films, the resistivity approaches the values reported for the best bulk crystals at room temperature, but the low-temperature resistivity is limited by structural twins. This work shows that the combination of MBE growth and a postgrowth anneal provides a route to creating high-quality films in this interesting family of layered, triangular oxides.
| Original language | English |
|---|---|
| Article number | 093401 |
| Journal | Physical Review Materials |
| Volume | 3 |
| Issue number | 9 |
| DOIs | |
| State | Published - Sep 3 2019 |
Funding
This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division (MBE synthesis, physical characterization), and BES Computational Materials Sciences Program (electronic structure characterization). J.M.O was supported by the Laboratory Directed Research and Development Program (x-ray diffraction) of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. DOE. The electron microscopy work was performed as a user project at the Center for Nanophase Materials Sciences, a U.S. Department of Energy Office of Science User Facility (D.M. and R.R.U.). G.R. and S.O. are supported by the Gordon and Betty Moore Foundations EPiQS Initiative (GBMF4418). M.B. would like to acknowledge the QuantumEmX award from ICAM and the Gordon and Betty Moore Foundation through Grant No. GBMF5305 for travel support. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division (MBE synthesis, physical characterization), and BES Computational Materials Sciences Program (electronic structure characterization). J.M.O was supported by the Laboratory Directed Research and Development Program (x-ray diffraction) of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. DOE. The electron microscopy work was performed as a user project at the Center for Nanophase Materials Sciences, a U.S. Department of Energy Office of Science User Facility (D.M. and R.R.U.). G.R. and S.O. are supported by the Gordon and Betty Moore Foundation’s EPiQS Initiative (GBMF4418). M.B. would like to acknowledge the QuantumEmX award from ICAM and the Gordon and Betty Moore Foundation through Grant No. GBMF5305 for travel support. We would like to thank Scott Chambers for assistance in interpreting XPS spectra. This paper has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.
| Funders | Funder number |
|---|---|
| Center for Nanophase Materials Sciences | |
| ICAM | |
| U.S. DOE | |
| U.S. Department of Energy Office of Science | |
| U.S. Department of Energy | |
| Gordon and Betty Moore Foundation | GBMF4418 |
| Office of Science | |
| Basic Energy Sciences | |
| Oak Ridge National Laboratory | |
| Laboratory Directed Research and Development |