Characterization of buried interfaces using Ga Kα hard X-ray photoelectron spectroscopy (HAXPES)

Abstract

HAXPES enables the detection of buried interfaces with an increased photo electron sampling depth.

Elucidating the Mechanism of Self-Healing in Hydrogel-Lead Halide Perovskite Composites for Use in Photovoltaic Devices

“…It should be noted that at larger emission angles, surface roughness is often a limiting factor due to shadowing effects; thus, quantification obtained by conventional XPS (sampling depth of I 3d 5/2 = 6 nm) is believed to be more representative of the surface stoichiometry. 75,76 The N/Pb 2+ ratios at an estimated sampling depth of 42 nm were found to be 1.5 ± 0.3 for both the 0 and 5 wt % films, close to the nominal value of 1.0. This ratio reduces with sampling depth in the 0 wt % film to 0.5 ± 0.3 at 14 nm, likely to be due to degradation of the organic cation at the surface of the film caused by atmospheric exposure.…”

“…The I/Pb 2+ ratios at this depth were found to be 3.3 ± 0.4 and 2.9 ± 0.4 for the 0 and 5 wt % films, respectively, close to the nominal value for MAPI. It should be noted that at larger emission angles, surface roughness is often a limiting factor due to shadowing effects; thus, quantification obtained by conventional XPS (sampling depth of I 3d 5/2 = 6 nm) is believed to be more representative of the surface stoichiometry. , …”

HAXPES: Inelastic background for characterization of nanostructured materials

“…Since then, several papers have reported on HAXPES inelastic background analysis to successfully determine nanostructures buried at 50-200 nm depth. 12,[16][17][18][19][20][21][22][23][24][25] These studies proved the capability of HAXPES, combined with analysis of inelastically scattered photoelectrons, to determine the location, composition, widths, and possible diffusion and intermixing of deeply buried layers. The high energy photons needed were produced at synchrotrons.…”

“…Typically, the probing depth with HAXPES is larger than 10λ, and structures at depths $50 nm and in some cases larger than 100 nm and even up to $200 nm have been studied. 12,[16][17][18][19][20][21][22][23][24][25] This enables detection of structures buried below capping layers (which are often >20 nm thick) and thus allows, for example, for detection of the active layers below electrodes in electronic devices. Capping layers are also used in the form of organic or metal deposition on top of a material to enable preservation of the chemical state upon exposure to the atmosphere or safer handling of hazardous material like actinides, and this analysis allows to nondestructively study the layers below the capping layer.…”

“…Thus, in 2017, Cui et al 16 found that information on structures up to depth was obtained in a case where the background signal could be followed up to 1,000 eV below the peak energy. Typically, the probing depth with HAXPES is larger than , and structures at depths ~50 nm and in some cases larger than 100 nm and even up to ~200 nm have been studied 12,16–25 . This enables detection of structures buried below capping layers (which are often >20 nm thick) and thus allows, for example, for detection of the active layers below electrodes in electronic devices.…”