{101} 〈101̄〉 Twins in Mo-doped TiSi₂ thin films with the C54 structure

The defect structures in orthorhombic C54 crystallites in thin films of Mo-doped TiSi₂ produced by co-sputtering have been investigated by transmission electron microscopy. Almost all C54 crystallites contain a twin boundary parallel to (101), dividing a crystallite into two regions, each of which also contains many thin twins with the habit plane parallel to (001), which is inclined by about 45° from (101). Both of the two regions divided by the twin boundary parallel to (101) tend to have facets on (001) as well as thin twins with the habit plane parallel to (001). As a result, C54 crystallites exhibit a characteristic shape just like an oak leaf. While twins with the (001) habit plane have been observed in C54 crystallites in both binary and Mo-doped TiSi₂ thin films, those with the (101) habit plane are present only in Mo-doped TiSi₂ thin films. The twinning elements for (101) twins are determined to be K₁ = (101), η ₁ = [1̄01], K₂ = (001) and η₂ = [100]. The origin of (101) twins in Mo-doped TiSi₂ is discussed in terms of the change in the c/a axial ratio upon alloying TiSi₂ with Mo.