An evaporation source for ion beam assisted deposition in ultrahigh vacuum

We describe the design, construction, and operation of an ion beam assisted deposition source for molecular beam epitaxy in ultrahigh vacuum. At a typical deposition rate of a monolayer per minute, the source may be operated in each of five modes: using self-ions from the vapor, self-ion plus noble gas ions from an additional gas inlet, both pulsed or continuous, or with complete suppression of ions. The source is based on electron bombardment heating of a metal rod or a crucible while the ions generated from the vapor are focused electrostatically onto the sample. Additional ions may be extracted from a noble gas stream injected into the ionization region. Examples for each of the different modes are given for Co deposition onto Cu(111), a system known to resist layer-by-layer growth. (C) 2002 American Institute of Physics.