Measurement of the surface-growth kinetics of reduced TiO2(110) during reoxidation using time-resolved scanning tunneling microscopy
Smith, R. D.
Bennett, R. A.
- Publisher: American Physical Society
We have employed variable-temperature scanning tunneling microscopy (STM) to follow the kinetics of reoxidation of a nonstoichiometric TiO2 (110) single-crystal surface. The surface is seen to grow during reoxidation between 573 and 1000 K and at pressures from 5Ã—10-8 to 2Ã—10-6 mbar O2. The reaction proceeds by combination of gas-phase O2 with mobile interstitial Ti3+ from the bulk. The surface is observed to grow new layers of TiO2 in a cyclic process, resulting in the formation of alternate layers of (1Ã—1) and cross-linked (1Ã—2). The growth rate was calculated by measuring the area of new material grown on consecutive STM images of the same area. The rate shows a linear dependence upon oxygen pressure, with an Arrhenius plot indicating an activation barrier of âˆ¼25Â±4 kJ mol-1 (0.25Â±0.04 eV/O2 molecule) for the surface reaction.