Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5368944 | Applied Surface Science | 2009 | 6 Pages |
The change in work function during the phase transition of a Sc-O/W(1Â 0Â 0) system at high temperatures of 1500-1700Â K was investigated in order to elucidate the mechanism of the decrease in the work function of a (1Â ÃÂ 1)-Sc-O/W(1Â 0Â 0) surface. For the measurement of the work function using a secondary electron method at high temperatures, a sample holder was uniquely designed in order to suppress contributions of a large number of thermionic electrons emitted from a low-work-function surface. The obtained work function revealed that the change in work function strongly correlates with the coverage of Sc-O complexes, the stoichiometry of which is Sc1O1. The higher the coverage of ScO is, the lower the work function is, suggesting that the work function of the (1Â ÃÂ 1)-Sc-O/W(1Â 0Â 0) surface is reduced by the formation of ScO electric dipoles. Furthermore, the decrease in work function was modeled in combination with a previously reported kinetic model describing surface phenomena, i.e., the oxidation, oxygen desorption, diffusion and surface segregation of Sc-O complexes, during the phase transition of the Sc-O/W(1Â 0Â 0) surface at high temperatures. It was confirmed that the proposed model can explain the experimentally obtained change in work function very well. The value of the dipole moment of a ScO electric dipole was determined to be 2.7Â ÃÂ 10â30Â CÂ m.