Titanium disilicide nanostructures: two phases and their surfaces

Titanium disilicide spontaneously forms small islands at low coverages on S i(001). We have used scanning tunneling microscopy to image islands formed by evaporation with deposition and annealing temperatures in the range 650- 950 degrees C. At all temperatures some of the islands have surfaces that a re flat and parallel to the substrate surface. Atomic resolution images rev eal two different phases, depending on the annealing temperature. Up to 850 degrees we find two related (4 x 4) reconstructions, which can be interpre ted in terms of the (010) surface of the C49 TiSi2 phase. Following anneals at 850 degrees C and above we see features consistent with rows of atoms i n an unreconstructed (110) surface of C54 TiSi2. In neither temperature ran ge do the islands exhibit strained pseudomorphic epitaxy. (C) 1999 Publishe d by Elsevier Science B.V. All rights reserved.