The growth of NaCl on flat and stepped silver surfaces

The growth of thin NaCl layers at room temperature on a Ag(100) and a Ag(1, 1, 19) substrate has been investigated by LEED spot profile analysis, supplemented by EELS in order to clarify the electronic structure of the film. Our LEED analysis of NaCl/Ag(100) shows that the average orientation of the NaCl unit mesh is the same as that of the Ag substrate, but rotational mosaics are formed in the (100) plane. The angular distribution of rotational angles has a width of ± 9 degrees around the average direction. From this result we conclude that the direction of the substrate step edges determines the orientation of the NaCl islands. The steps of the vicinal silver surface are overgrown by elastic NaCl carpets. With increasing coverage, the modulation of the NaCl films by the step structure gets more and more washed out until, at around 10ML, the whole film is only tilted by the nominal miscut of the sample. Closed films are only found at a thickness larger than 4ML, as concluded from EELS