The incommensurate nature of epitaxial titanium disilicide islands on Si(001)

Much of traditional metallurgy depends on manipulating thermodynamic and ki netic constraints to achieve the desired microstructure. It is becoming app arent that it may be possible to exploit similar principles to achieve desi gner self-assembled nanostructures on surfaces. A key question in determini ng equilibrium island sizes is whether epitaxial growth occurs with commens urate lattice parameters (with corresponding elastic strain), or whether th e islands are relaxed. In the case of TiSi2 islands on Si(001), be can show both by STM and by TEM that the C49 phase is incommensurate, and that the islands have the relaxed silicide lattice parameters. The STM images show t his both from the dimensions of surface reconstructions and from subtle cur rent imaging contrast that we attribute to the periodic nature of the islan d/substrate interface. The TEM evidence comes primarily from analysis of mo ire fringes, and the electron diffraction data confirm the presence of the C49 phase. (C) 2000 Elsevier Science B.V. All rights reserved.