Pseudo-C11b Phase Formation of Titanium Disilicide During the C49 to C54 Transition

Abstract

The formation of TiSi2 thin films using the SALICIDE process on doped and undoped silicon substrates was studied. XRD TEM, AES, RBS and four probe Rs were used to characterize the material. Unit cell parameters and energetics were determined. Results confirm electrical and chemical signatures consistent with the known C49 conversion to C54. However, XRD indicated a structurally different intermediate phase occurs during the C49 to C54 transformation. Modeling was performed based on C11b structure (14/mmm) type, with the Ti and Si atoms arranged similarly to those in MoSi2. The unit cell was determined to be a = 4.428 Å, b = 4.779 Å, c = 9.078 Å with a Fmmm space group and total pseudo-potential plane wave calculations based on crystallographic simulations of −103.96 ev/Atom.

Novel Rhenium Carbides at 200 GPa

“…69), a=4.428 Å, b=4.779 Å, c=9.078 Å, V=192.1 Å 3 ). [25] The shortest Si-Si distance in oF-TiSi2 at ambient conditions is ~2.57 Å (compare to ~2.35 Å in diamond-structured Si), [26] which is close to ~2.54 Å in C54-type structured oF-TiSi2 and to ~2.53 Å in a Zintl phase CaSi.…”

“…Those defects might help to stabilize the structure. In fact, the titanium disilicide oF ‐TiSi 2 , which is isostructural to oF ‐ReC 2 (discussed above), is calculated to have the energy of about 0.3 eV/atom higher, than other titanium disilicide polymorphs . However, further studies are required to elaborate this hypothesis.…”

“…Some crystal‐chemical analogy can be considered also, but it does not allow to make any definite conclusion regarding the chemical bonding in this particular case. Indeed, oF ‐ReC 2 is isostructural to one of the polymorphs of titanium disilicide (TiSi 2 ) (space group Fmmm , #69), ( a = 4.428 Å, b = 4.779 Å, c = 9.078 Å, V = 192.1 Å 3 ) . The shortest Si–Si distance in oF ‐TiSi 2 at ambient conditions is ≈ 2.57 Å that is ca.…”