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

We have grown single-crystal thin films of Ti2GeC and T3GeC2 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 degrees 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 mu Omega cm. The lowest value is obtained for phase-pure T3GeC2(0001) films,