Giant faceting of vicinal Si(001) induced by Au adsorption

4 degrees vicinal Si(001) shows perfectly ordered terraces with a width of 4 nm which are separated by double steps. Adsorption of Au at 800 degrees C : results in a dramatic change of the step morphology: the surface decompos es into areas which are perfectly flat with a (001) orientation and (119) f acets, which compensate for the macroscopic miscut. Extremely straight supe rterraces with a length limited only by the size of the sample (here 4 mm) and a width ranging from 400 nm to 4 mu m are formed by massive Si mass tra nsport. The extreme aspect ratio of 1:10000 of this submicron structure is attributed to a heterogeneous nucleation process. SPA-LEED reveals a new, Au-induced incommensurate 5 x 3.2 reconstruction ab ove a critical coverage as the driving force for the formation of large elo ngated (001) terraces. LEEM shows the strongly anisotropic nucleation proce ss in: vivo. Dark field imaging and microspot LEED techniques have been use d to determine the influence of the different 5 x 3.2 domain orientations o n the growth behavior of the (001) superterraces. The majority of domain te rraces grow with a speed of more than 10 mu m per second. The width and are a of the (001) terraces increase proportionally to the Au coverage. The ste ps of the vicinal surface are accumulated in irregular step bunches. With f urther increasing Au coverage the step bunches are transformed into well-de fined facets with a (119) orientation, as determined by SPA-LEED. The kinetics of the faceting process have been studied with SPA-LEED, REM, STM, and light diffraction using a HeNe laser, because the typical size of the superterraces is of the order of the wavelength of visible light: the r esulting structure is visible to the bare eye. The parallel arrangement of superterraces acts as an irregular optical phase grating: illumination with white light results in stripes of all possible diffraction colors.