Preparation of semi-transparent V2AlC thin films using the thermionic vacuum arc technique: crystal and substrate effects on the electrochemical performance

Among the MAX phases, vanadium aluminum carbide (V2AlC) is one of the remarkable elements due to its superior properties. These intriguing properties stem from physical characteristics such as crystallinity, grain size, and so on, which further affect its electrochemical performance. One of the major and significant issues in this way is using an appropriate substrate to form the desired crystal orientation. According to the results, the crystal nature of the substrate and conductive layer illuminates the formation of polycrystalline V2AlC with various preferential orientations. This subject also directly changed the electrochemical performance, Li-ion diffusion, and resistivity of the V2AlC thin film. The XRD, high-resolution XPS, and Raman spectroscopy results revealed V2AlC formation on all substrates. In all cases, the surface characteristics were confirmed nano-dimensional growth, with a high level of compactness, homogeneity, and a crack-free landscape. Moreover, the optical measurements exhibited semi-transparency of the thin film with lower disorder but higher cutoff energy when coated upon the ITO/PET substrate. The electrochemical results highlighted that the V2AlC coated upon the ITO/PET platform outperforms due to non-Faradaic behavior, lower disorder, and small grain size, facilitating Li-ion diffusion and more capacity storage behavior inside the aqueous LiClO4-PC (0.1 M). Subsequently, the selected material paved the way for using it as a promising candidate in metal-ion storage.