| In this research, investigations of thin film MAX phase ternary carbides synthesized by magnetron sputtering and a combinatorial method in the temperature range of RT-1000°C are reported. The M2AC MAX phases that formed in the following systems, Ti-Nb-Al-C, V-Cr-Al-C, V-Cr-Ge-C, were examined. In all solutions, only mixing of the M elements was investigated. All textured films grew epitaxially (c-axis) on c-sapphire substrates or deposited binary carbide buffer layers. The lowest synthesis temperature resulting in textured growth was for V 2AlC at 600°C, however; formation of nanocrystalline Cr2AlC was observed at 550°C as indicated by Raman spectroscopy. High temperature X-ray diffraction of amorphous Cr-Al-C and Cr-Ge-C films showed textured growth of the MAX phase occurred around 650°C, and 725°C, respectively. All combinatorial studies were performed at 850°C with (Ti1- xNbx)2AlC films grown on TiC buffer layers while (V1-xCr x)2AlC and (V1-xCr x)2GeC grown directly on sapphire. Complete solubility across the entire range of x was observed for all systems. Additionally, new thin film phases of V3AlC2, V 4AlC3, Nb5Al3Cx, Cr 5Ge3Cx, (Ti1- xNbx)3AlC2, (Ti1-xNbx) 4AlC3, and (V1-xCr x)4AlC3 were discovered.;The M-element impacts many different properties of MAX phase films. The surface of most films were rough, some containing large hexagonal crystals. Yet, this work has demonstrated that the surface roughness can be tuned using elemental substitutions on the M-sites. While friction testing found all films to have relatively low coefficients of friction (<0.12), this too was found to be influenced by the M-element. Raman spectroscopy of (Ti1- xNbx)2AlC films indicates possible stiffening around x = 0.75 explicitly demonstrating the role of the M-element in this solid solution. All films were good electrical conductors with metal-like conduction down to 2K with magnitude and temperature dependence of the resistance tunable through composition. The Hall coefficient and magnetoresistance were also controlled by M-element substitution. While dramatic changes have not been observed, it is clear that the application of combinatorial methods has improved the understanding of the role of the M-element in determining the properties of MAX phases improving the ability to use the materials for thin film applications and beyond. |
