Ion-assisted deposition has evolved from a collection of individual “recipes” to the use of ion energy per deposited atom as a measure of this dose, to the variation of this dose with material melting temperature. The energy range of interest for most applications has narrowed, focusing at present on the low energy range from about 25eV to about 100eV. Dense, low-defect films are believed to be generated in this range by lattice vibrations. Ion collision effects tend to be confined to the surface below -25eV, while damage is introduced by the excessive penetration of ions above -100eV.