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

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-UHVmanipulator 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 O2 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.

Evolution of surface and sub-surface morphology and chemical state of exsolved Ni nanoparticles

“…This was done using a recently developed system enabling simultaneous in situ APXPS and APGIXS measurements on the same sample region. 16 The X-ray scattering geometry is shown in Fig. 4a, along with an illustration of its orientation with respect to the APXPS aperture of the hemispherical analyzer.…”

“…More details on this setup can be found in ref. 16. A stainless steel beamstop was applied to block the reflected specular X-ray beam from saturating or even damaging the CCD camera.…”

“…In this work, we monitor the chemistry and morphology of Ni nanoparticles as they migrate from SrTi 0.9 Nb 0.05 Ni 0.05 O 3− δ (STNNi) hosts during reducing treatments in H 2 using a recently developed combination of ambient pressure X-ray photoelectron spectroscopy (AP-XPS), and ambient pressure grazing incidence X-ray scattering (AP-GIXS). 16 Ni reduces as it migrates to the surface, forming metallic nanoparticles partially embedded within the perovskite host lattice. Meanwhile, the oxidation state of the Sr and Ti in the host is mostly unchanged during the exsolution process.…”

Spiers Memorial Lecture: prospects for photoelectron spectroscopy

“…In general, there is a strong push to combine NAP-XPS with structural techniques and/or lateral resolution. In addition to grazing incidence X-ray scattering, 101 examples include its combination with SWAPPS 53,55–57 (Section 2.7), where there are now prospects to extend the technique to studies at elevated temperature, 57 and near-edge X-ray absorption fine structure (NEXAFS). 102 Combination with scanning photoelectron microscopy (SPEM) adds lateral imaging capability to the picture, and is implemented with NAP-XPS, for example, at the ESCA Microscopy beamline at Elettra (Trieste), offering sub-μm resolution.…”

Multimodal X-ray probe station at 9C beamline of Pohang Light Source-II

“…The near-and far-field scattering profiles and images can be recorded simultaneously using this probe. In addition, this has application in the investigation of the chemical information and electronic structure of materials by measuring X-ray absorption/emission spectra with the tunable energy of synchrotron X-rays and photoelectron spectroscopy simultaneously (Sanchez-Cano et al, 2021; Timoshenko & Cuenya, 2021; Kersell et al, 2021).…”