The basic features of surface dual modes are investigated on the plasma slab. The integral of kinetic wave dispersion relation is evaluated to derive the wave frequency as well as the relevant Landau damping decrement of the electrostatic surface modes by employing the functional perturbation (FP) method. The influence of the ion thermal motion and geometrical effects is examined on the damping rate of surface dual modes. It is shown that the damping rate is an increasing function with the ion temperature, as this effect becomes more important for middle values of the wavenumbers. It is also shown that the propagation of the surface waves in plasma slab is more difficult than that of the semi-infinite plasma due to their interaction with the additional boundary conditions. We found that the spectral analysis of the surface modes plays a vital role as a diagnostic tool to account for the geometrical effects on the surface waves.
