the techniques of selective silicon growth (ssg) have already found many applications in device fabrication in respect of both process simplification and the development of novel device structures: the techniques involve selective epitaxial growth (seg), epitaxial lateral overgrowth (elo), selective polycrystalline si growth (spd) and selective polycrystalline-epitaxial growth (speg or sspd). the basic technique involves substrate preparation to produce the necessary seed windows in an insulating layer together with the subsequent removal of surface damage (e.g. from a reactive ion etch), ex-situ and in-situ cleaning processes and the selective growth itself. ex-situ processing generally involves combinations of a wet chemical (e.g. rca) clean to remove organics and/or metallics, hf treatment to remove oxide and (hydrogen) passivate the si surface against reoxidation and/or uv-ozone (uvoc) exposure designed to remove carbon and to provide a thin passivating oxide. the in-situ clean can be a combination of an hf-vapour treatment providing a similar surface to the above, uvoc providing the same treatment as above (but with the production of a relatively thinner passivating oxide which is more easily desorbed at low temperatures), followed by some sort of plasma clean or a h/sub 2/ bake to remove the surface oxide prior to growth: however, depending upon the particular reactor system being used, an in-situ 'pre-bake' may not be necessary if operating under ultrahigh vacuum conditions. the ex-situ and in-situ cleaning procedures should provide substrate surfaces adequate for ss