The production and use of ultralow energy ion beams

An ion accelerator, purpose built to produce beams at energies down to 10 e V with current densities in the 10-100 mu A cm(-2) range, is described. Fit ted with dual ion source assemblies, the machine enables ultralow energy io n implantation and the growth of films and multilayers to be carried out un der highly controlled conditions. The accelerator delivers ion beams into a n ultrahigh vacuum chamber, containing a temperature controlled target stag e (range -120 to +1350 degrees C), where they are used to study the fundame ntal physics relating to the interaction of ultralow energy ions with surfa ces. This knowledge underlies a wide range of ion-beam and plasma-based tec hnologies and, to illustrate its importance, results are presented from inv estigations designed to determine the optimum conditions for the growth of diamond-like and aluminum films by ion-beam deposition and the formation of ultrashallow junctions in semiconductors by 2.5 keV As+ implantation. The later investigation shows how transient arsenic diffusion, which occurs dur ing post-implant thermal processing, can be controlled by manipulating the substrate temperature during implantation. (C) 2000 American Institute of P hysics. [S0034-6748(00)55502-6].