Segregation of K at the TiO2(100) surface

We have studied the segregation of potassium to the surface of TiO2(100) us ing Auger electron spectroscopy (AES), low energy electron diffraction (LEE D), direct recoil spectroscopy (DRS), and mass-spectroscopy of recoiled ion s (MSRI). It is found that the concentration of potassium at the surface is strongly influenced by the sample temperature. MSRI results indicate the p resence of potassium starting at annealing temperatures of 675 K and the su bsequent disappearance above 875 K. Conversely, AES only indicates the pres ence of potassium after annealing the sample to 975 K. Together these resul ts indicate that below 875 K, potassium exists in the very topmost surface layer, while above 875 K, potassium is located below this layer. (C) 1999 E lsevier Science B.V. All rights reserved.