Photoelectron spectroscopy of transition metal oxide interfaces

Abstract

Abstract. In the present paper we review applications of the photoelectron spectroscopy (PES) technique to the investigation of transition metal oxide (TMO) interfaces. We summarize very briefly some of the principle, specific characteristics of TMOs. Because of the buried nature of the interfaces, the photoelectrons must penetrate certain thicknesses of material, which is easier with higher kinetic energies in the keV range. Thus, we also briefly summarize some of the hallmarks of hard X-ray photoelectron spectroscopy (HAXPES), before presenting four explicit samples of the analysis of TMO interfaces: The LaAlO 3/SrTiO3(0 0 1) interface, which had attracted attention because of the discovery of a sheet of high mobility electrons below the thin layer of LaAlO3; superlattices of the two insulators CaCuO2 and SrTiO3, which can be prepared to become superconducting at about 40 K; epitaxial films of the 90 K superconductor GdBa2Cu3O 7−δ on NdGaO3; and finally the analysis of the nucleation of the 90 K superconductor YBa2Cu3O 7−δ on SrTiO3(0 0 1). The latter two cases of the investigation of the superconducting films are examples of photoelectron spectroscopy by X-ray standing wave (XSW) excitation. Because of this, the bare essential features of the XSW technique are also briefly reviewed.

Layer-Resolved Cation Diffusion and Stoichiometry at the LaAlO3/SrTiO3 Heterointerface Probed by X-ray Photoemission Experiments and Site Occupancy Modeling

“…Possible developments of the present angle-resolved method include the use of HAXPES , to be more bulk sensitive and gain further information on stoichiometry at the interface by contrasting and comparing the soft X-ray with hard X-ray results.…”

Epitaxial ferroelectric interfacial devices

“…x-ray diffraction and scattering; [127][128][129] of the electronic state and band alignment via x-ray photoemission spectroscopy (XPS); [130][131][132][133][134] and of the electronic band structure using x-ray absorption spectroscopy (XAS). [135][136][137][138][139][140][141] With the advent of free electron laser sources, 142 capable of producing extremely intense, highly transverse coherent, and ultra-short (few fs long) pulsed x-ray beams, it is now possible to investigate ultrafast dynamical processes in ferroelectric systems, including phonon dynamics and ultrafast switching induced by strong THz light beams.…”

Thermodynamic stability and control of oxygen reactivity at functional oxide interfaces: EuO on ITO

“…We employ hard X-ray photoelectron spectroscopy (HAXPES) as a powerful nondestructive and element-sensitive probing technique. 19,20 HAXPES enables the chemical depth profiling of the functional oxide layer and the buried heterointerfaces, as schematically depicted in Fig. 1.…”