Epitaxial Ti₂GeC, Ti₃GeC₂, and Ti₄GeC₃ MAX-phase thin films grown by magnetron sputtering

We have grown single-crystal thin films of Ti₂GeC and Ti₃GeC₂ and a new phase Ti₄GeC₃, as well as two new intergrown MAX-structures, Ti₅Ge₂C₃ and Ti₇Ge₂C₅. Epitaxial films were grown on Al₂O₃(0001) substrates at 1000 °C using direct current magnetron sputtering. X-ray diffraction shows that Ti–Ge–C MAX-phases require higher deposition temperatures in a narrower window than their Ti–Si–C correspondences do, while there are similarities in phase distribution. Nanoindentation reveals a Young’s modulus of 300 GPa, lower than that of Ti₃SiC₂. Four-point probe measurements yield resistivity values of 50–200 μΩcm. The lowest value is obtained for phase-pure Ti₃GeC₂(0001) films.