Nanoscale Surface Analysis of High Entropy Alloy

TL;DR

This study employs nano-IR spectroscopy to analyze the nanoscale surface properties of high entropy alloys, revealing spectral features and discussing potential for 3D surface characterization.

Contribution

It demonstrates nano-IR hyperspectral imaging of HEAs at 20 nm resolution and explores polarization analysis for advanced surface analysis.

Findings

Increased absorption at 900-1100 1/cm band in HEA CuPdAgPtAu.

Spectral features consistent with Drude-Lorenz permittivity modeling.

Potential for extending nano-IR to full 3D surface orientation analysis.

Abstract

Nanoscale surface analysis of 1 micrometer thick high entropy alloys (HEAs) was carried out using nano-IR for hyperspectral imaging and single point spectroscopy in the 700-1700 1/cm spectral range. Nano-IR is based on the detection of scattered light from an oscillating metal coated nano-tip in one of the arms of the Fourier transform infrared spectrometer and has a resolution defined by the tip radius of the probe, 20 nm, regardless of the excitation wavelength. HEA CuPdAgPtAu showed an absorption and reflection increase at 900-1100 1/cm band, which is consistent with Drude-Lorenz modeling of permittivity, however, could also signify oxide formation as tested by X-ray photoelectron spectroscopy of CuPdAgPtAu and CrFeCoNiCuMo. Realization of polarization analysis for nano-IR nano-spectroscopy in the plane perpendicular to the sample's surface is discussed and modeled. The currently available modality of surface analysis with the excitation-detection mode of the p-pol. antenna can be extended to full 3D analysis of the orientational dependencies of local absorbance and refractive index.