LOW-ENERGY ION-SCATTERING INVESTIGATION OF THE ORDER-DISORDER TRANSITION IN THE FIRST ATOMIC LAYER OF THE CU3AU(100) SURFACE

The first investigation of order parameter by low energy ion scatterin g (LEIS) is reported here. The temperature dependence of the short-ran ge order parameter for the first atomic layer of Cu3Au(100) was studie d by LEIS using K+ scattered from Au-Au pairs. In contrast to the bulk , the order-disorder transition in the first layer appears to be a con tinuous function of the temperature. It was found that the transition in the first atomic layer starts at about 500 K. Moreover, this work s hows, for the first time, that the local order at alloy surface can be studied by low energy ion scattering with sensitivity to one monolaye r.