Thin Film Synthesis and Characterization of New MAX Phase Alloys

Sammanfattning: The objective of this Thesis is synthesis and characterization of new MAX phase alloys (M = early transition metal, A = A-group element, and X = C or N) based on incorporation of M and X elements previously not used in any known MAX phases. This is motivated by a search for optimized and unique materials properties, such as different magnetic states.Two synthesis routes have been used to attain Ti2AlC1-xOx: deposition of Ti2AlCy under high vacuum conditions with residual gas acting as O source, and solid-state reactions following deposition of understoichiometric TiCy on Al2O3. Detailed local quantification by analytical transmission electron microscopy (TEM) including electron energy loss spectroscopy (EELS) shows up to 13 at.% O within high quality MAX phase structure. According to previous theoretical work, the range of experimentally obtained O content is enough to observe drastic changes in the materials anisotropic electronic properties. Calculations on effect of substitutional O on shear deformation have also been performed.In a recent theoretical study by Dahlqvist et al., (Cr,Mn)2AlC has been predicted as a new stable magnetic nanoscale laminate. Inspired by this work, thin films of (Cr,Mn)2AlC, as well as of a neighboring system (Cr,Mn)2GeC, have been synthesized by magnetron sputtering. Incorporation of 8 and 12.5 at.% of Mn, respectively, has been detected by analytical TEM including EELS and energy dispersive X-ray spectroscopy (EDX). The total saturation moment of 0.36μB per Mn atom at 50 K has been measured by vibrating sample magnetometry (VSM) for a (Cr,Mn)2GeC sample, providing the first experimental evidence of a magnetic MAX phase.The experimental results obtained in this Thesis provide a base for expanding the MAX phase definition and materials characteristics into new areas, towards further fundamental understanding and functionalization.