| AVS 60th International Symposium and Exhibition | |
| Magnetic Interfaces and Nanostructures | Monday Sessions |
| Session MI+EM+MG-MoA |
| Session: | Frontiers of Complex Oxides |
| Presenter: | F. Mao, Uppsala University, Sweden |
| Authors: | F. Mao, Uppsala University, Sweden T. Nyberg, Uppsala University, Sweden T. Thersleff, Uppsala University, Sweden U. Jansson, Uppsala University, Sweden |
| Correspondent: | Click to Email |
Delafossites AMO2 (A= Cu,Ag, Pd, Pt; M=Fe, Co, Ni, Cr, Al, Mn, etc) have received considerable attention due to their potential applications as transparent conducting oxides, photocatalysts, luminescent materials, batteries and thermoelectric materials. Recently, high temperature superconductivity was also suggested for doped members of this type of oxide compounds. Many of the interesting properties of delafossites are related to the crystal structure where linear O-A-O bonds connect layers of slightly distorted edge-sharing MO6 octahedra. Consequently, the delafossites can be described as natural nanolaminates of MO2 layers separated by A atoms.
Copper-based delafossite materials have been studied intensely through synthesis of solid-state reaction, hydrothermal synthesis method, sol-gel methods and, in a few cases, reactive sputtering with high temperature post-annealing (≥700oC). To our knowledge, however, no studies have previously been published on silver-based delafossite films deposited directly by sputtering. The main challenge is that the silver based delafossites tend to decompose at high temperature (>400oC). Furthermore, the synthesis of Ag-based delafossites by reactive sputtering is usually restricted to small window of stoichiometric composition and also the sputtering condition.
The combinatorial materials science enables rapid discovery and optimization of new or known materials for creating ’’library’’ of composition-structure-property relationship. Compared with the ‘’one-at-a-time’’ sputtering, the combinatorial sputtering with large composition gradient is powerful tool for time-saving and economical development of silver-based delafossite films.
In this work, we demonstrate the combinatorial deposition of delafossite AgFeO2 thin films using co-sputtering of silver and iron targets in a reactive Ar-O2 mixture atmosphere. Rapid screenings of XRD, XPS, XRF were employed to determine the chemical composition and phase structure. The most interesting parts of the materials were studied by TEM. Optical and electrical properties have also been investigated. Our results show that the AgFeO2 films have been successfully deposited by the combinatorial reactive sputtering without post-annealing but the process window is very narrow and strongly dependent on deposition temperature, sputtering power ratio, pulse frequency, O2 flow rate, working pressure, etc. The XRD and TEM showed that the AgFeO2 films grew epitaxially with the direction of (00l) in the optimal sputtering condition.