Electrodeposition for the Guided Synthesis and Screening of Binary Alloy Thin Films

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Alloy coatings can enhance the mechanical and electrochemical properties of engineering materials such as surface hardness, wear resistance, catalytic performance, and corrosion resistance. The development and testing of alloy films requires extensive time and experimentation due to the non-monotonic variation of many properties with alloy composition and the large experimental space of compositions, which increases rapidly with the number of components in the alloy. The development time of alloy thin films can be reduced by analyzing many compositions in a single experiment. However, many current thin film deposition-based gradient synthesis techniques are expensive, produce a limited experimental range of compositions, and may not vary the composition of each component independently. Electrodeposition is an attractive technique for thin film deposition due to its low cost, high scalability, and sensitivity to the geometry of the deposition environment, but conventional co-electrodeposition of multiple metals from a single electrolyte bath suffers from limited compositional control and experimental range. We report an electrodeposition-based method that produces a wide range of compositions on a single sample with good compositional control. To demonstrate, we coated samples of polished Cu with NiCo alloys with gradient local composition. The composition, phase, morphology, and performance of the NiCo thin films are investigated using a range of high-resolution techniques including x-ray fluorescence spectroscopy, synchrotron X-ray diffraction, SEM, and nanoindentation.