AVS 49th International Symposium
    Surface Science Wednesday Sessions
       Session SS-WeP

Paper SS-WeP18
Pd adatom-Adatom Interactions on the W (211) Surfaces

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Surface Science Poster Session
Presenter: T.-Y. Fu, National Taiwan Normal University, ROC
Authors: T.-Y. Fu, National Taiwan Normal University, ROC
Y.-J. Hwang, National Taiwan Normal University, ROC
T.T. Tsong, Academia Sinica, Taiwan
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Adatom-adatom interactions play an important role in controlling the formation of surface layers, thin film growth and catalysis. Direct observations in the field ion microscope make it possible to determine the probability P(R) of finding two atoms at a separation R at equilibrium on a surface at temperature T. The free energy of interaction F(R) can be obtained from the relation: P(R) is proportional to exp[-F(R)/kT]. On W (211) planes, the interactions of two Pd atoms are studied in following cases: two Pd atoms in the same channel, in two nearest neighboring channels, in two next nearest neighboring channels, and so on. When two Pd atoms are in the same channel, they combine easily to form a dimer of bond length 2.74 Å and the dimer can diffuse along the channel. In the other cases, the oscillatory behaviors of interactions along the channel direction are observed. The more is the number of the separate channels, the smaller is the interaction energy maximum. The energy maximum in the same channel, two nearest neighboring channels, and two next nearest neighboring channels are 37.5 meV, 23.0 meV, and 9.0 meV, respectively.