X-ray Spectroscopy of a Rare-Earth Molecular System Measured at the Single Atom Limit in Room Temperature

TL;DR

This study demonstrates the detection of X-ray signals at the single-atom level in a rare-earth molecular system at room temperature, using advanced microscopy and spectroscopy techniques.

Contribution

It introduces a method to measure X-ray absorption and tunneling currents at the single-atom level in a molecular system at room temperature.

Findings

X-ray-induced photocurrent correlates with La ion coverage.

Clear M4,5 absorption edges observed in X-ray absorption spectra.

X-ray excited tunneling current detected at the atomic scale.

Abstract

We investigate the limit of X-ray detection at room temperature on rare-earth molecular films using lanthanum and a pyridine-based dicarboxamide organic linker as a model system. Synchrotron X-ray scanning tunneling microscopy is used to probe the molecules with different coverages on a HOPG substrate. X-ray-induced photocurrent intensities are measured as a function of molecular coverage on the sample allowing a correlation of the amount of La ions with the photocurrent signal strength. X-ray absorption spectroscopy shows cogent M4,5 absorption edges of the lanthanum ion originated by the transitions from the 3d3/2 and 3d5/2 to 4f orbitals. X-ray absorption spectra measured in the tunneling regime further reveal an X-ray excited tunneling current produced at the M4,5 absorption edge of La ion down to the ultimate atomic limit at room temperature.