Towards a New Reference Material—Analytical Challenges in Examining High‐Entropy Alloy Thin Films

ABSTRACT A new high‐entropy alloy (HEA) consisting of titanium, chromium, manganese, iron, and nickel was deposited as a thin‐film on silicon substrates using magnetron sputtering from a novel segmented target composed of metal stripes. This material was explored with the goal to create a new reference material for surface analysis and evaluation of complex composite materials. The film's morphology was initially characterized by scanning electron microscopy (SEM), followed by crystallographic analysis using X‐ray diffraction (XRD) and selected area electron diffraction (SAED). The two‐dimensional compositional homogeneity was assessed using a combination of scanning and transmission electron microscopy (TEM) with energy‐dispersive spectroscopy (EDS), X‐ray fluorescence (XRF), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), and X‐ray photoelectron spectroscopy (XPS). The in‐depth chemical composition was further analysed using ToF‐SIMS and Auger electron spectroscopy (AES). Our findings demonstrate that it is possible to produce thin HEA films with a homogeneous in‐depth composition from a segmented target. Notably, despite the fixed composition of the target, we were able to vary the HEA's composition by exploiting inhomogeneities within the magnetrons sputter plasma. Additionally, we successfully created HEA films with significant compositional gradients.