Corrosion and Structural Properties of Erbium–Zinc Thin Films at Low-to-Medium Erbium Concentrations

摘要

A combinatorial erbium–zinc thin film material library is deposited by thermal co-evaporation. The library is screened for its structural and compositional properties by energy-dispersive X-ray (EDX), X-ray diffraction (XRD), and scanning electron microscopy (SEM), and shows a compositional range from 3.1 to 31.2 at% Er. XRD proofs an amorphous region around 20 at% Er. This is rarely encountered in binary systems, and supports an improved corrosion resistance for this composition. SEM shows the formation of a compact film at the same compositional range. The alloys' electrochemical characteristics are assessed with open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS), cyclic voltammetry, and potentiodynamic polarization measurements in a scanning droplet cell microscopy (SDCM) setup coupled with an inductively coupled plasma optical emission spectrometer (ICP–OES). This allows capturing the relation between current, potential, and metal ion dissolution in the system. The experiments are performed in aqueous 0.01 M Na_2SO_4 solution under constant flow (0.0136 mL s~(-1)). Increased corrosion resistance is found for alloys containing 19–22 at% in all four used methods, showing the superior properties at this compositional range.