Adsorbate induced mesoscopic surface reconstruction of the system Te/Pd(1 0 2)

Low energy electron diffraction (LEED) measurements have been carried out on the clean and Te covered Pd(1 0 2) surface. This is the surface into which the Pd(1 0 0) surface is reconstructed by a concentration of more than 0.5 ML of Te. The Pd(1 0 2) surface was produced with a terrace width of more than 1000 Å. Up to 0.5 ML the adsorption of Te takes place on the flat (1 0 2) surface, on which islands with (2×1) structure are formed coupled with a reduction of the terrace widths to about half the initial value. Above 0.5 ML, and up to 1 ML, the adsorbed Te atoms produce a structural change of the surface, i.e. a terrace structure is formed with a clear average terrace length that depends on Te concentration and with step edges in [2̄ 0 1] direction. As concluded from the characteristic splitting of LEED spots as a function of energy, these terraces occupy only two height levels in an alternating sequence and are separated by steps of single atomic height. The terrace width of the alternating terraces increases with increasing Te-concentration. Again a flat surface is formed at 1 ML of Te. A geometrical model is established and discussed.