Unraveling Charge Transfer at Oxide Heterointerfaces
The Science
When different materials meet to form an interface, they can exhibit unique behaviors not seen in each material alone. These behaviors result from the complex interactions found at the interface. One important phenomenon is the directional movement of charges across those boundaries. To reveal whether charge transfer can persist at interfaces composed of relatively stable systems governed by ionic bonding, researchers synthesized heterostructures of lanthanum nickel oxide/lanthanum iron oxide (LNO/LFO). Their findings revealed clear evidence of charge transfer from iron (Fe) to nickel (Ni). They also observed that the thickness of the LFO layer significantly affects charge distribution at the interface, which can be used to fine-tune material behavior.
The Impact
Understanding and controlling charge transfer at material interfaces is crucial for maximizing the potential of advanced electronic and energy technologies. This work underscores the importance of precise interface engineering and highlights the need to establish control over transport properties and electronic states by managing the direction and magnitude of the interfacial charge transfer. It also emphasizes the importance of considering alternatives to the traditional ionic bonding paradigm, especially in systems with strong 3d–2p orbital hybridization, offering new insights for designing materials with enhanced functionality.
Summary
Over the past decade, LNO-based superlattices have drawn significant interest given their potential for high-temperature superconductivity through heterostructure formation. However, consensus has yet to be reached on the direction and magnitude of charge transfer in LNO/LFO superlattices and heterostructures. It has been suggested that charge transfer may not occur in LNO/LFO heterostructures due to the high stability of the Fe3+ species.
A team of researchers recently provided clear evidence of charge transfer from Fe to Ni at the LNO/LFO heterointerfaces. They confirmed this through a combination of theoretical calculations and various experimental techniques. Their theoretical modeling revealed that the electron transfer from LFO to LNO and subsequent rearrangement of the Fe 3d band create an unexpected metallic ground state within the LFO layer. They synthesized a set of LNO/LFO superlattices via molecular beam epitaxy and measured changes in the oxidation states of Ni and Fe. It was revealed that the oxidation state on Ni drops from Ni3+ to Ni3-δ and the oxidation state on Fe increases from Fe3+ to Fe3+δ. Quantitative analysis indicates electron transfer up to 0.5 e-/interface from Fe to Ni in the LNO/LFO superlattices. They established a direct link between the magnitude of interfacial charge transfer and the measured sheet resistance of the LNO/LFO superlattices. Notably, the thickness of the LFO layer significantly impacts how charge is redistributed at the interface, which in turn affects the in-plane transport properties of the superlattices. This research highlights the critical role of precise interface engineering in creating materials with desired electronic functionalities.
Contact
Yingge Du, Pacific Northwest National Laboratory, yingge.du@pnnl.gov
Funding
This work was supported by the Department of Energy (DOE), Office of Science (SC), Basic Energy Sciences, Division of Materials Sciences and Engineering, Synthesis and Processing Science Program, under FWP 10122. This research used resources of the National Energy Research Scientific Computing Center, a DOE SC user facility supported under Contract No. DE-AC02-05CH11231 using NERSC award BES-ERCAP0028636. Work at the University of Minnesota – Twin Cities (UMN) was supported primarily by the Air Force Office of Scientific Research through Grant Nos. FA9550-21-1-0025, and FA9550-23-1-0247 with partial support from the UMN MRSEC program under Award No. DMR-2011401. Parts of this work were carried out at the Characterization Facility, UMN, which receives partial support from the National Science Foundation (NSF) through the MRSEC program under award DMR-2011401. Device fabrication was carried out at the Minnesota Nano Center, which is supported by the NSF through the National Nano Coordinated Infrastructure under award ECCS-2025124.
Legal Disclaimer:
EIN Presswire provides this news content "as is" without warranty of any kind. We do not accept any responsibility or liability for the accuracy, content, images, videos, licenses, completeness, legality, or reliability of the information contained in this article. If you have any complaints or copyright issues related to this article, kindly contact the author above.
