Determination of surface debye temperatures by leed

The method to determine the surface Debye temperature by LEED beam intensity versus temperature measurements is critically evaluated. Simulated in( I) versus T plots obtained with the help of the Gallon-model using a kinematic approach for the specular beam at Bragg diffraction conditions are presented. It is shown that the assumed linearity in these plots is fundamentally incorrect. With our newly developed model good agreement is obtained with experimentally determined effective Debye temperature versus electron energy plots for Pt(111), Pt(100), Rh(111) and Rh(100). However, it is shown that the method of electron energy variation is not reliable for straightforward determination of the surface Debye temperature, whereas variation of angle of incidence is better suitable. In addition, plots measured on a Pt-Rh(100) surface with a Pt surface content varying between 25 and 60 at% are compared with simulated plots for disordered and ordered alloys.