Phase formation in the interfacial reactions of ultrahigh vacuum deposited titanium thin films on (111)Si

摘要

Phase formation in the interfacial reactions of ultrahigh vacuum deposited Ti thin films on (111)Si has been studied byinsitureflected high energy electron diffraction (RHEED) and transmission electron microscopy (TEM).InsituRHEED and high resolution TEM data showed unambiguously that there is considerable intermixing of Ti and Si atoms during Ti deposition. Ti5Si3was found to be the first nucleated phase followed by Ti5Si4and TiSi. Ti5Si3, Ti5Si4, TiSi, and C49hyphen;TiSi2along withahyphen;interlayer were found to form in samples annealed at 475thinsp;deg;C for 30 and 60 min. Ti5Si4was the first silicide phase to disappear followed by Ti5Si3then TiSi. In samples annealed at 700thinsp;deg;C for 10 min, C54hyphen;TiSi2started to appear. To understand the thermodynamic origin of the phase formation, metastable free energy diagrams at 450ndash;600thinsp;deg;C have been constructed. Ti5Si3and C49hyphen;TiSi2were found to have the highest and lowest driving force, respectively. On the other hand, Ti5Si4has the lowest interface energy. The sequence of formation and disappearance of silicide phases is discussed accordingly.