Digital Control of Terrace Width of One-dimensional Semiconductor Surfaces by Modification of Lattice Strain

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The clean Si (110) surface shows a "16x2" reconstruction, where one-dimensional up-and-down terraces arrange alternatively. The terrace width is about 2.5 nm and the height difference between the adjacent terraces is one atomic layer, 0.2 nm. This surface is a promising substrate for future low-dimensional electronic devices as well as nano-biomaterials. In this study, we have tried to control the terrace width by a unique method using metal adsorption. This is based on the idea that the surface stress plays a role to determine the surface step density. The metal we used is a tin, which belongs the same periodic table as silicon, because homovalent doping does not so much affect electronic structures on the surface. At 0.2 ML adsorption of Sn on the surface, the 16x2 changed into 28x2, which was confirmed by low-energy electron diffraction as well as scanning tunneling microscopy. STM observation shows that Sn atoms forms trimers which are inserted accordingly into the silicon pentagonal clusters. As a result, surface stress was reduced to make the terrace width being enlarged to about 50%. In addition of structural point of view, we attempted to modify electronic nature of the up-and-down terraces by hydrogen termination technique. The result shows that, at the initial stage of reaction, atomic hydrogen reacts with specific atoms in pentagonal cluster to reduce surface stress, and that the up-and-down structure is kept at a saturation coverage of hydrogen, demonstrating the potential of this surface even in air. Ag and Ba deposition on Si(110) are now in progress