Investigation of the Ti/MgCl₂ interface on a Si(111) 7 × 7 substrate

Photoelectron spectroscopy with synchrotron radiation, low energy electron diffraction, and ion-scattering spectroscopy were used in order to study the Ti/MgCl₂ interface grown on an atomically clean Si(111) 7 × 7 substrate. A series of high resolution spectra after deposition of a thick MgCl₂ layer, step by step deposition of Ti and gradual annealing, indicated a very reactive interface even at room temperature. Strong interaction between the incoming Ti atoms and the MgCl₂ layer, leads to the formation of Ti²⁺ and Ti⁴⁺ oxidation states. The interfacial interaction continues even at multilayer Ti coverage mainly by the partial disruption of Mg–Cl bonds and the formation of Ti–Cl sites, rendering this interface a very promising UHV-compatible model of a pre-catalyst for olefin polymerization. After the final annealing, the MgCl₂ multilayers desorb while Ti remains on the surface forming a silicide layer on which Cl and Mg atoms are attached.