AVS 46th International Symposium
    Surface Science Division Monday Sessions
       Session SS1+EM-MoA

Paper SS1+EM-MoA1
Nucleation and Growth of Copper Islands on TiO@sub2@(110): Evidence for Self-limited Island Sizes

Monday, October 25, 1999, 2:00 pm, Room 606

Session: Metals on Oxides
Presenter: D.A. Chen, University of South Carolina
Authors: D.A. Chen, University of South Carolina
M.C. Bartelt, Sandia National Laboratories
R.Q. Hwang, Sandia National Laboratories
K.F. McCarty, Sandia National Laboratories
Correspondent: Click to Email
Metal-oxide interfaces play an important role in a variety of technological applications, including those involving the design of electronic devices, sensors and heterogeneous catalysts. In order to develop a fundamental understanding of these metal-oxide interfaces, we have studied the formation of Cu islands on TiO@sub2@(110)-(1x1) in ultrahigh vacuum using scanning tunneling microscopy for Cu coverages up to 1.25 ML. The formation of 3D islands at all the coverages reflects the relatively high mobility of Cu atoms on TiO@sub2@ at room temperature and the weak interactions between Cu and TiO@sub2@. Surprisingly, the island diameter remains almost constant for all coverages. Furthermore, the Cu islands exhibit self-limiting growth at low coverages (<0.5 ML) since the average island size remains essentially constant with increasing coverage while the island density increases. At the higher coverages (>0.5 ML), the average island size scales with coverage, but this increase in island size is primarily due to an increase in height not diameter. Although larger islands can be formed by annealing, the average size of the islands is independent of coverage for any given annealing temperature. We propose two general schemes that could lead to the observed self-limiting growth. The first is that the attachment rate of adatoms drops as the island size increases. The second is that the rate at which adatoms reach existing islands drops as the islands grow. We will discuss physical scenarios under which each of these effects may be dominant. This work was performed under the U.S. Department of Energy contract DE-AC04-94AL85000 and supported in part by the USDOE-OBES-Division of Materials Sciences.