Correlation of morphology and electrical properties of nanoscale TiSi2 epitaxial islands on Si (001)

The morphology and electrical properties of nanoscale epitaxial islands of TiSi2 are explored. The TiSi2 islands are prepared by ultra-high vacuum (UHV) deposition of ultra-thin Ti (0.3-2 nm) on both smooth and roughened Si (001) substrates. The roughened substrates are prepared by etching with atomic H produced in a plasma. The island formation is initiated by annealing to 800-1000 degrees C. The morphologies of the substrate before and after island formation are examined by atomic force microscopy (AFM). In particular, the influence of surface-roughness on both the formation of islands and the size distribution of islands is investigated. Islands with a lateral dimension of similar to 35 nm and a vertical dimension of similar to 2.5 nm on a roughened substrate (RMS = 12 nm) were observed, with a uniform distribution of 120 nm spacing between the islands. It was found that for similar processing conditions the size distribution of islands formed on a rough surface was smaller than islands formed on smooth surfaces. The results are discussed in terms of surface energy, diffusion and the strain field around the islands. The island structures can affect the electrical characteristics of the interface and the Schottky barrier was obtained from diodes formed with a Pt layer deposited over the islanded interface. The Schottky barrier was lowest for interfaces with the smaller TiSi2 islands. (C) 1997 Elsevier Science S.A.