X-ray photoemission and resistivity studies of the Pd-covered Ce thin films

TL;DR

This study investigates Ce/Pd bilayer thin films grown on SiO2 substrates, using X-ray photoelectron spectroscopy and resistivity measurements to analyze their oxidation resistance, electronic states, and transport properties.

Contribution

It provides new insights into the oxidation prevention and electronic behavior of Ce thin films with Pd overlayers, combining surface and electrical characterization techniques.

Findings

Pd layer effectively prevents Ce oxidation

Ce f states are near the border between fluctuating valence and localization

Transport properties show Kondo, semiconducting, and metallic behaviors

Abstract

We have fabricated Ce/Pd bilayers grown on the SiO$_2$ substrate by magnetron sputtering under ultrahigh vacuum. Usage of palladium layer on top of the Ce film appears to prevent effectively the sample oxidation. The thickness of the cerium films is between 10 - 200 nm and 10 nm-thick palladium overlayers are always used. We have performed $in - situ$ X-ray photoelectron spectroscopy on the as-deposited films and $ex - situ$ electrical resistivity measurements and XRD characterization. XPS confirms a very good quality of the samples. The analysis of the Ce $3d$ spectrum suggests that the $f$ states of Ce are on the border between the fluctuating valence and localization. The resistivity measurements reveal a competition of the Kondo scattering, semiconducting and metallic behaviors as well as the influence of the dimensional effect.