Growth of Ti3SiC2 thin films by elemental target magnetron sputtering

Epitaxial Ti3SiC2(0001) thin films have been deposited by dc magnetron sputtering from three elemental targets of Ti, C, and Si onto MgO(111) and Al2O3(0001) substrates at temperatures of 800-900 degreesC. This process allows composition control to synthesize M(n+1)AX(n) (MAX) phases (M: early transition metal; A: A-group element; X: C and/or N; n=1-3) including Ti4SiC3. Depositions on MgO(100) substrates yielding the Ti-Si-C MAX phases with (10 (1) over bar5), 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 Ti3SiC2 nucleation due to kinetic limitations at substrate temperatures below 700 degreesC. Instead, there is a competitive TiCx growth with Si segregation to form twin boundaries or Si substitutional incorporation in TiCx. Physical properties of the as-deposited single-crystal Ti3SiC2 films were determined. A low resistivity of 25 muOmega cm was measured. The Young's modulus, ascertained by nanoindentation, yielded a value of 343-370 GPa. For the mechanical deformation response of the material, probing with cube corner and Berkovich indenters showed an initial high hardness of almost 30 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. (C) 2004 American Institute of Physics.