Oxygen migration at Pt/HfO2/Pt interface under bias operation

Abstract

The interfacial electronic states of a Pt/HfO2/Pt diode were investigated by using hard x-ray photoelectron spectroscopy under bias operation. The application of a forward bias to the Pt/HfO2/Pt diode increased the Pt–O bonding peak, providing evidence of Pt electrode oxidization and oxygen vacancy formation around the Pt/HfO2 interface. Under a reverse bias, hafnium was drawn to the Pt electrode, where it took part in Hf–Pt bonding. We achieved the direct observation of oxygen migration at a Pt/HfO2 interface under device operation, which is the key to controlling the electrical properties of metals on oxides.

Electronic and electrical properties of functional interfaces studied by hard X-ray photoemission

“…where the quantities (E Pt4f7/2 -E F ), (E Ti2p3/2 -VBM) BTO and (E Pt4f7/2 -E Ti2p3/2 ) are measured by HAXPES on clean bulk Pt, BaTiO 3 and Pt/BaTiO 3 bi-layers, respectively. Similar measurements can be performed for the Fe/BaTiO 3 bi-layers.…”

“…In particular, a range of phenomena referred to as "resistive switching" effects in metal oxide based metal-insulator-metal (MIM) multilayers has been identified and is currently being investigated targeting the development of the novel non-volatile memory applications. Hard X-ray photoelectron spectroscopy (HAXPES) combining brilliant X-ray undulator radiation from 3rd generation sources with commercially available optimized high-energy electron spectrometers has recently emerged as an excellent tool providing information on the chemical and electronic structure of prototype functional oxide based multilayered stacks thereby enabling new insight into the physical mechanisms behind the resistance switching effects in ultrathin metal oxide films [2][3][4]. The use of hard X-rays in an energy range of about 2.5-12 keV is particularly beneficial since it produces photoelectrons with variable high kinetic energies yielding large electron inelastic mean free paths which results in electron escape depths up to about 20 nm.…”

Bias application hard x-ray photoelectron spectroscopy study of forming process of Cu/HfO2/Pt resistive random access memory structure

“…3 We demonstrated the resistance switching behavior of the Cu/HfO 2 /Pt system. 13 Although the formation of a filament on an anode has been reported by several groups, 11,12,14 there has been no direct observation of metal ionization and diffusion at a metal/oxide interface under bias operation.…”

“…8 We observed the Pt electrode oxidization and oxygen vacancy formation at the interface of the Pt/HfO 2 /Pt system directly using hard x-ray photoelectron spectroscopy (HX-PES) under bias operation. 13 The other mechanism is the filament model, which describes the generation and rupture of a metal filament where a metal such as Ag or Cu acts as a fast mobile ion in oxides, which is also called nanoionics-based resistive switching. 1,11,12 Sakamoto et al reported the creation of a Cu metal filament in Ta 2 O 5 via an electrochemical reaction.…”

In situ x-ray photoelectron spectroscopy for electrochemical reactions in ordinary solvents

“…A bias voltage application was performed as previously reported. 17 The potential of the Si membrane with respect to the Cu tape was controlled by a potentiostat (HSV-110, Hokuto Denko). Figure 2(A) shows a current-potential (I-V) relation of the Si membrane in contact with water (blue).…”