Studies Of Si(5 5 12) And Facets Observed On It By Scanning Tunneling Microscopy

Technology which reduces the size of nanodevice component by traditional top-down method has reached its technical limits. Therefore, the so-called bottom-up method becomes the main research areas of surface physics to produce controllably atomic, molecular, nano-scale quantum functional identical structure through over the whole surface. Up to now, in order to take advantages of Si(5 5 12) which is composed of well defined one-dimensional structure to fabricate nanodevices, some studies of the surface atomic structure, adsorption properties are reported. However, report of systemcal studies about the facets observed on the Si(5 5 12) surface is rarely seen. These phenomena will be illastrated in this study.Clean Si(5 5 12) terrace is observed by ultra-high vacuum scanning tunneling microscopy (STM). Alternating Si(7 7 17) facet and Si(5 5 12) facet show the average surface orientation from [7 7 17] to [5 5 12] exists within the angle between the two surfaces. A wide Si(7 7 17) facet combined with Si(1 1 3) facet is also observed. Si(3 3 7) facet, Si(1 1 2) facet, Si(1 1 1) facet are observed on Si(5 5 12) terrace, their heights which is related to Si(5 5 12) terrace are studied. It reveals that if the height between Si(5 5 12) terrace is higher than the height between Si(1 1 1) facet and Si(5 5 12) terrace, Si(1 1 1) facet appears; If the height between Si(5 5 12) terrace is lower than the height between Si(1 1 1) facet and Si(5 5 12) terrace, higher than the height between Si(1 1 2) facet and Si(5 5 12) terrace, Si(1 1 2) facet appears; If the height between Si(5 5 12) terrace is lower than the height between Si(1 1 2) facet and Si(5 5 12) terrace, higher than the height between Si(3 3 7) facet and Si(5 5 12) terrace, Si(3 37) facet appears. The observed phenomena reveals that:in the process of surface reconstruction, the whole surface will tend to equilibrium state which is balanced between surface tension and intrinsic surface stress, terrace and step are uniformly distributed. But due to some factors, such as direct current heating, adsorption of impurities, defects etc., there will be somewhat different from the equilibrium shape. So there is a terrace width fluctuation (i.e.step height fluctuation) on the surface. In other words, the distribution structure of step and terrace will change. That is the reason why many kinds of facets can be observed on the Si(5 5 12) surface. When Si(7 7 17) facet combined with Si(5 5 12) facet, crystal surface from the Si(7 7 17) to the Si (5 5 12) is weakly anisotropic in y-plot, the cusped minimum of y-plot becomes sharpness, equilibrium crystal shape is connected by rounded parts. Due to some local surface tension, a wide Si(7 7 17) facet can be observed. Due to the surface free energy of Si(1 1 1) facet is the lowest, followed by Si(1 1 2) facet, again is Si(3 3 7) facet, they will appear in the difference position with the confined height (width).