Titanium silicide island formation on an Si(001)-(2 × 1) surface was studied by means of scanning tunneling microscopy (STM) in situ at high temperature. Just after the start of annealing at 873 K, homogeneous nucleation occurs on the terrace, while preferential growth at the step edges was observed upon prolonged annealing. As the titanium silicide islands grow, multiple steps are formed nearby. The island size distribution was analyzed at several temperatures. Two types of TiSi2 structures, namely C49 and C54, were identified from the scanning tunneling spectroscopy (STS) spectra, in accordance with first-principles calculations. There was a critical island size for the transformation of C49–C54.

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Using scanning tunneling microscopy, we observed the formation process of ruthenium silicide on a monolayer Ru-deposited Si(001) surfaces at high temperature. Ruthenium silicide islands of nanometer scale are formed after heating to 1400 K. They tend to be aligned in the [110] and ½1 10 directions. Locally observed spectroscopic results were compared with other spectral data. Large islands showed compositional inhomogeneity, with a widened band gap near the interface with the Si substrate, suggesting that growth of the islands occurs due to incorporation of Si atoms from the edges of nearby steps.

The formation and growth of Ru-Si islands were observed on a ruthenium-deposited Si(111) surface during successive cycles of heating for 30 s at 1423 K and cooling. Lateral and vertical growth is analysed. The large lattice mismatch of small Ru2Si3 islands with the Si substrate modulates a Volmer-Weber type growth mode. When the islands are large, Ru2Si3 crystals are situated on a metastable buffer layer.

The thermal formation of silicide was observed on Ru -deposited Si(001) surfaces at monolayer scale. Rectangular Ru–Si islands, composed of metastable Ru -rich granular phase, were formed at the early stage of growth. The shape and size of the islands were strongly influenced by the orientation of Si(001) , and did not change until the density of the nearby steps became sufficiently high. In the late stage of growth, incorporation of Si into the islands starts, and at the same time the frequent attack of Si detached from the terrace results in formation of step bunches on the terrace.