From Doping to Dilution: Local Chemistry and Collective Interactions of La in HfO2

Abstract

Lanthanum (La) doping is considered as a promising route to overcome reliability issues of switchable ferroelectric HfO2-based devices. This study links the local chemistry at the La lattice sites with local and collective electronic properties of the La:HfO2 matrix using hard X-ray photoelectron spectroscopy. The satellite structure of the La 3d core level, the plasmonic excitation energies, and core-level rigid binding energy shifts are investigated for La:HfO2 samples with a wide range of La doping, ranging from 3.5% to 33%, i.e., from the doping to dilution level. The emerging chemical phases and electronic properties are discussed as a function of La content. From the evolution of the plasmon excitation energies and rigid binding energy shifts, it is concluded that electronic charge compensation by oxygen vacancies occurs for increasing La content.