Abstract
Phase formation in the interfacial reactions of ultrahigh vacuum deposited Ti thin films on (111)Si has been studied by in situ reflected high energy electron diffraction (RHEED) and transmission electron microscopy (TEM). In situ RHEED and high resolution TEM data showed unambiguously that there is considerable intermixing of Ti and Si atoms during Ti deposition. Ti 5 Si 3 was found to be the first nucleated phase followed by Ti 5 Si 4 and TiSi. Ti 5 Si 3 , Ti 5 Si 4 , TiSi, and C49-TiSi 2 along with a-interlayer were found to form in samples annealed at 475°C for 30 and 60 min. Ti 5 Si 4 was the first silicide phase to disappear followed by Ti 5 Si 3 then TiSi. In samples annealed at 700°C for 10 min, C54-TiSi 2 started to appear. To understand the thermodynamic origin of the phase formation, metastable free energy diagrams at 450-600°C have been constructed. Ti 5 Si 3 and C49-TiSi 2 were found to have the highest and lowest driving force, respectively. On the other hand, Ti 5 Si 4 has the lowest interface energy. The sequence of formation and disappearance of silicide phases is discussed accordingly.