Thermally-induced formation of Si wire array on an ultrathin (111) silicon-on-insulator substrate

Abstract

We have found that a Si wire array is formed by thermal agglomeration of an ultrathin (111) Si layer in a bonded silicon-on-insulator (SOI) structure, although previous studies for crystalline and amorphous Si layers on SiO2 only showed island formation. As starting material, (111) bonded SOI wafers with the top Si layers thinned to 5–9 nm were used. The samples were then subjected to a thermal treatment at 950 °C in an ultrahigh vacuum. Atomic force microscopy revealed that the (111) top Si layer is deformed into three sets of wire arrays in the three equivalent ⟨112¯⟩ directions. It is also shown that the patterning of a Si layer leads to the wire array selectively formed in one of these three directions.