Synthesis and characterization of Zr2Al3C4 thin films

• Nearly phase pure epitaxial Zr2Al3C4 thin films were grown on 4 H–SiC(001) substrates.
• Intergrowth of ZrC phase can be observed when Al is deficient during growth.
• Suppression of competing phases can be achieved by increasing temperature on Al2O3(001).
• Substrate selectivity of Zr2Al3C4 phase is explained by lattice mismatch and substrate quality.
• Very similar growth behavior to the known MAX phases were observed for Zr2Al3C4.

Zr2Al3C4 is an inherently nanolaminated carbide where layers of ZrC alternate with layers of Al3C2. Characterization of bulk samples has shown it has improved damage tolerance and oxidation resistance compared to its binary counterpart ZrC. Though a potential candidate for coatings applied for use in harsh environments, thin films of Zr2Al3C4 have not been reported. We have synthesized epitaxial Zr2Al3C4 thin films by pulsed cathodic arc deposition from three elemental cathodes, and have studied the effect of incident atomic flux ratio, deposition temperature, and choice of substrate on material quality. X-ray diffraction analysis showed that Zr2Al3C4 of the highest structural quality was obtained for growth on 4 H–SiC(001) substrate at 800 °C. Also, suppression of competing phases could be achieved on α-Al2O3(001) at elevated substrate temperatures. Very similar growth behavior to that of the well-known Mn + 1AXn phases – Al supersaturation, binary carbide intergrowth and high sensitivity to choice of substrate – indicates a strong connection between the two families of materials, despite their differences in structure and in chemistry.