The effects of Si layer thickness on thermal agglomeration of a (111) bonded silicon-on-insulator (SOI) structure were studied. As starting material, (111) bonded SOI wafers with their top Si layer thinned to 2-9 nm were used. The samples were subjected to thermal treatment at 950 degrees C in ultrahigh vacuum. Atomic force microscopy revealed that, in the 4-9 nm thickness range, the top Si layer is deformed into wire arrays in the < 112 > directions. However, at thicknesses below 4 nm, randomly formed Si islands were observed. This structural transition from wires to islands is presumably due to the atomic-scale thickness fluctuation in the initial Si layer. (c) 2005 Elsevier B.V. All tights reserved.