Simultaneous ambient pressure X-ray photoelectron spectroscopy and grazing incidence X-ray scattering in gas environments

TL;DR

This paper introduces a novel experimental system that combines X-ray photoelectron spectroscopy and grazing incidence X-ray scattering to analyze surface structure, composition, and chemical activity of samples in gas environments simultaneously.

Contribution

The study presents a new integrated setup enabling concurrent XPS and GIXS measurements in gas pressures up to multi-Torr, with a versatile pivoting-UHV-manipulator for detector positioning.

Findings

Successful measurement of chemical state, composition, and structure of Ag-behenate in different atmospheres.

Demonstrated capability to analyze samples in ambient conditions with simultaneous structural and chemical probes.

System can be retrofitted into existing synchrotron instruments for advanced gas-phase surface studies.

Abstract

We have developed an experimental system to simultaneously observe surface structure, morphology, composition, chemical state, and chemical activity for samples in gas phase environments. This is accomplished by simultaneously measuring X-ray photoelectron spectroscopy (XPS) and grazing incidence X-ray scattering (GIXS) in gas pressures as high as the multi-Torr regime, while also recording mass spectrometry. Scattering patterns reflect near-surface sample structures from the nano- to the meso-scale. The grazing incidence geometry provides tunable depth sensitivity while scattered X-rays are detected across a broad range of angles using a newly designed pivoting-UHV-manipulator for detector positioning. At the same time, XPS and mass spectrometry can be measured, all from the same sample spot and in ambient conditions. To demonstrate the capabilities of this system, we measured the chemical state, composition, and structure of Ag-behenate on a Si(001) wafer in vacuum and in O$_2$ atmosphere at various temperatures. These simultaneous structural, chemical, and gas phase product probes enable detailed insights into the interplay between structure and chemical state for samples in gas phase environments. The compact size of our pivoting-UHV-manipulator makes it possible to retrofit this technique into existing spectroscopic instruments installed at synchrotron beamlines. Because many synchrotron facilities are planning or undergoing upgrades to diffraction limited storage rings with transversely coherent beams, a newly emerging set of coherent X-ray scattering experiments can greatly benefit from the concepts we present here.