STM study on two-dimensional electronic system localized on surfaces

There are some surface electronic states which can be regarded as two dimensional electronic system. Their properties have been studied using novel techniques of scanning tunneling microscopy (STM). Two examples of such surfaces; Si(111)7x7 structure and Au(111), are presented. It was found that behavior of electrons in such states are strongly affected by chemical (adsorbates) and morphological (steps or islands) properties of the surfaces.