TOF-LEIS spectra of Ga/Si: Peak shape analysis

Low energy ion scattering (LEIS) is used to characterize Ga layers deposited onto Si(1 1 1)-(7 × 7) substrates at different deposition temperatures. The Ga/Si system exhibits a pronounced 3D island growth and thus is a suitable object to investigate the relation between LEIS-peak shapes and the morphology of thin films. It is shown that up to a certain critical depth (a few MLs) the single scattering component can be used as a measure of the number of surface Ga atoms per unit area. If a higher amount of Ga is deposited, the single scattering model is not valid anymore and multiple scattering becomes significant. The Ga peak starts to be asymmetric with a well developed multiple scattering component. Such a component can be utilized for the observation of the morphology of the layers. It was found that the more intensive the 3D growth of adsorbed Ga atoms on the Si(1 1 1) substrate, the more pronounced is the multiple scattering yield for a given amount of Ga.