Nanostructures are produced on metal and semiconductor surfaces in a controllable manner via low energy ion bombardment. The resultant materials are probed with scanning probe microscopy, x-ray photoelectron spectroscopy and low energy ion scattering. A variety of nanostructures such as ripple, dot and hole are formed and controlled their shapes and sizes by tuning the ion beam parameters and ion target geometry. The self-organized nanoclusters produced by ion bombardment display quantum size effects. Neutralization of scattered alkali-metal ions is used to probe the electronic states of the nanoclusters.The work function change accompanying oxygen adsorption on metals is not always positive, as would be expected due to the surface dipole. I shall also discuss that the low energy alkali ions could be used to investigate the contribution of the dipole to the local potential near a Ta surface atom
