Nucleation and growth processes have long been studied using diffraction technique On semiconductor surfaces, localized defects strongly affect both the electron properties of the surfaces as well as their reactivity, therby affecting nucleat and growth. In order to identify the role of local electronic structure, and surface irregularities such as steps and defects, a real-space probe of electronic structure is needed. Scanning tunneling microscopy is capable of probing both the local surface geometry and local electronic structure, permitting adsorption and chemical reactivity to be studied on an atom-by-atom basis.
