Thin films of $M_{n+1}A{X}_n$ layered compounds in the $\mathrm{Ti}\text{−}\mathrm{Si}\text{−}\mathrm{C}$ system were deposited on $\mathrm{MgO}\left(111\right)$ and ${\mathrm{Al}}_2{\mathrm{O}}_3\left(0001\right)$ substrates held at $900°\mathrm{C}$ using dc magnetron sputtering from elemental targets of $\mathrm{Ti}$, $\mathrm{Si}$, and $\mathrm{C}$. We report on single-crystal and epitaxial deposition of ${\mathrm{Ti}}_3{\mathrm{SiC}}_2$ (the previously reported $MAX$ phase in the $\mathrm{Ti}\text{−}\mathrm{Si}\text{−}\mathrm{C}$ system), a previously unknown $MAX$ phase ${\mathrm{Ti}}_4{\mathrm{SiC}}_3$ and another type of structure having the stoichiometry of ${\mathrm{Ti}}_5{\mathrm{Si}}_2{\mathrm{C}}_3$ and ${\mathrm{Ti}}_7{\mathrm{Si}}_2{\mathrm{C}}_5$. The latter two structures can be viewed as an intergrowth of 2 and 3 or 3 and 4 $M$ layers between each $A$ layer. In addition, epitaxial films of ${\mathrm{Ti}}_5{\mathrm{Si}}_3{\mathrm{C}}_{\mathrm{x}}$ were deposited and ${\mathrm{Ti}}_5{\mathrm{Si}}_4$ is also observed. First-principles calculations, based on density functional theory (DFT) of ${\mathrm{Ti}}_{n+1}{\mathrm{SiC}}_n$ for $n=1$,2,3,4 and the observed intergrown ${\mathrm{Ti}}_5{\mathrm{Si}}_2{\mathrm{C}}_3$ and ${\mathrm{Ti}}_7{\mathrm{Si}}_2{\mathrm{C}}_5$ structures show that the calculated difference in cohesive energy between the $MAX$ phases reported here and competing phases ($\mathrm{TiC}$, ${\mathrm{Ti}}_3{\mathrm{SiC}}_2$, ${\mathrm{TiSi}}_2$, and ${\mathrm{Ti}}_5{\mathrm{Si}}_3$) are very small. This suggests that the observed ${\mathrm{Ti}}_5{\mathrm{Si}}_2{\mathrm{C}}_3$ and ${\mathrm{Ti}}_7{\mathrm{Si}}_2{\mathrm{C}}_5$ structures at least should be considered as metastable phases. The calculations show that the energy required for insertion of a $\mathrm{Si}$ layer in the $\mathrm{TiC}$ matrix is independent of how close the $\mathrm{Si}$ layers are stacked. Hardness and electrical properties can be related to the number of $\mathrm{Si}$ layers per $\mathrm{Ti}$ layer. This opens up for designed thin film structures the possibility to tune properties.

Epitaxial ${\mathrm{Ti}}_3{\mathrm{SiC}}_2\left(0001\right)$ thin films have been deposited by dc magnetron sputtering from three elemental targets of $\mathrm{Ti}$ , $\mathrm{C}$ , and $\mathrm{Si}$ onto $\mathrm{MgO}\left(111\right)$ and ${\mathrm{Al}}_2{\mathrm{O}}_3\left(0001\right)$ substrates at temperatures of $800–900°\mathrm{C}$ . This process allows composition control to synthesize ${\mathrm{M}}_{n+1}{\mathrm{AX}}_n$ (MAX) phases ($\mathrm{M}$ : early transition metal; $\mathrm{A}$ : $\mathrm{A}$ -group element; $\mathrm{X}$ : $\mathrm{C}$ and∕or $\mathrm{N}$ ; $n=1–3$ ) including ${\mathrm{Ti}}_4{\mathrm{SiC}}_3$ . Depositions on $\mathrm{MgO}\left(100\right)$ substrates yielding the $\mathrm{Ti}–\mathrm{Si}–\mathrm{C}$ MAX phases with $\left(10\overline{1}5\right)$ , as the preferred orientation. Samples grown at different substrate temperatures, studied by means of transmission electron microscopy and x-ray diffraction investigations, revealed the constraints of ${\mathrm{Ti}}_3{\mathrm{SiC}}_2$ nucleation due to kinetic limitations at substrate temperatures below $700°\mathrm{C}$ . Instead, there is a competitive ${\mathrm{TiC}}_x$ growth with $\mathrm{Si}$ segregation to form twin boundaries or $\mathrm{Si}$ substitutional incorporation in ${\mathrm{TiC}}_x$ . Physical properties of the as-deposited single-crystal ${\mathrm{Ti}}_3{\mathrm{SiC}}_2$ films were determined. A low resistivity of $25\mu \Omega \mathrm{cm}$ was measured. The Young’s modulus, ascertained by nanoindentation, yielded a value of $343–370\mathrm{GPa}$ . For the mechanical deformation response of the material, probing with cube corner and Berkovich indenters showed an initial high hardness of almost $30\mathrm{GPa}$ . With increased maximum indentation loads, the hardness was observed to decrease toward bulk values as the characteristic kink formation sets in with dislocation ordering and delamination at basal planes.