The interfacial properties of MgCl_2 thin films grown on Ti(0001)

摘要

Photoelectron spectroscopy with synchrotron radiation (SRPES), temperature programmed desorption (TPD), low energy electron diffraction (LEED), and ion-scattering spectroscopy (ISS) were used in order to study the MgCl _2 /Ti (0001) interface. A clear hexagonal LEED pattern confirmed the presence of a quite large grain of Ti(0001) on the substrate while no new superstructure was formed after deposition of MgCl_2 either at room or at elevated temperatures. A series of high resolution spectra after step by step MgCl_2 deposition and gradual annealing indicated strong interaction between MgCl_2 and the substrate while ISS measurements showed that there is no migration of Ti atoms into the deposit layers. Additional quantities of deposited MgCl_2 grew stoichimetrically on top of the chemically active interface. Annealing at ～350 °C caused clustering of the MgCl_2 multilayer and TPD results showed that they desorbed stoichimetrically at temperatures between 360 and 380 °C. The interfacial TiClx_(Mgy) species dissociated by the disruption of the Cl-Mg bonds at temperatures higher than 400 °C and metallic Mg evaporated. The Cl atoms remained attached on the Ti surface but they did not form any ordered structure even after annealing at 730 °C. The present results indicate the occurrence of charge transfer at the Ti/ MgCl_2 interface through the Cl ligands and provide valuable information for catalyst design.