Cr${}_2$GeC thin films were grown by magnetron sputtering from elemental targets. Phase-pure Cr${}_2$GeC was grown directly onto Al${}_2$O${}_3$(0001) at temperatures of 700–800 °C. These films have an epitaxial component with the well-known epitaxial relationship Cr${}_2$GeC(0001)//Al${}_2$O${}_3$(0001) and ${\mathrm{Cr}}_2\mathrm{GeC}\left(11\overline{2}0\right)//{\mathrm{Al}}_2{\mathrm{O}}_3\left(1\overline{1}00\right)$ or ${\mathrm{Cr}}_2\mathrm{GeC}\left(11\overline{2}0\right)//{\mathrm{Al}}_2{\mathrm{O}}_3\left(\overline{1}2\overline{1}0\right).$ There is also a large secondary grain population with $\left(10\overline{1}3\right)$ orientation. Deposition onto Al${}_2$O${}_3$(0001) with a TiN(111) seed layer and onto MgO(111) yielded growth of globally epitaxial Cr${}_2$GeC(0001) with a virtually negligible $\left(10\overline{1}3\right)$ contribution. In contrast to the films deposited at 700–800 °C, the ones grown at 500–600 °C are polycrystalline Cr${}_2$GeC with $\left(10\overline{1}0\right)$-dominated orientation; they also exhibit surface segregations of Ge as a consequence of fast Ge diffusion rates along the basal planes. The room-temperature resistivity of our samples is 53–66 μΩcm. Temperature-dependent resistivity measurements from 15–295 K show that electron-phonon coupling is important and likely anisotropic, which emphasizes that the electrical transport properties cannot be understood in terms of ground state electronic structure calculations only.

• Received 30 March 2011

DOI:https://doi.org/10.1103/PhysRevB.84.075424