Band alignment at memristive metal-oxide interfaces investigated by hard x-ray photoemission spectroscopy

Abstract

The electronic structure and band alignment at metal/oxide interfaces for nonvolatile memory applications are investigated by hard x-ray photoelectron spectroscopy (HAXPES) and DC transport measurements, using acceptor doped SrTiO 3 as a model memristive oxide. Metal-insulator-metal (MIM) structures with a noble metal (Pt) top electrode form a Schottky barrier and exhibit rectifying properties, while a reactive metal (Ti) as top electrode shows symmetric I(V) characteristics and a flat band situation at the interface. The transition from rectifying to ohmic I(V) relations with increasing Ti thickness is discussed with respect to the electrochemical reaction at the interface, the band alignment at the electrode/oxide interface, and the slope of the energy bands across the MIM structure.

Hard X-ray PhotoElectron Spectroscopy of transition metal oxides: Bulk compounds and device-ready metal-oxide interfaces

“…HAXPES is able to provide depth sensitivity into the bulk even beyond 50 nm [61,20], thus large enough to perform non-destructive studies of deep regions and buried interfaces [62], e.g., for metal-oxide-semiconductor structures [63], oxide-oxide heterojunctions [64,65], metal-oxide interfaces for nonvolatile memory applications [66,67] or metal-organic interfaces of hybrid spintronic devices [68]. Core level spectra representative for the upper Ti electrode and the underlying PCMO were collected, namely Ti 2p and Mn 2p, for systems set in four different states.…”

Hard x-ray photoelectron spectroscopy of tunable oxide interfaces

“…9 Furthermore, performing HAXPES experiments in operando, i.e., under applied bias voltage, both the band alignment and the chemical of a M/I device can be determined under realistic operation conditions-and captured in a concurrent measurement. 37,38 In this chapter, we discuss an Au/NiFe 2 O 4 /SrTiO 3 heterostrocture as a prototype example for an in operando HAXPES experiment, as schematically sketched in Fig. 8.…”

Reactive metal–oxide interfaces: A microscopic view

“…At the same time, the Cr atoms become ionized and strongly dope the near-interface region, forcing E F above the conduction band minimum. 001) heterojunctions, where the metallic electrode was either the noble metal Pt or the highly reactive metal Ti [123]. In the former case, the junction was found to exhibit rectifying properties, whereas in the latter the interface exhibits flat-band electronic structure and symmetric I(V) characteristics.…”