The surface binding energy in slow collisional sputtering

Abstract

Slow collisional sputtering, in which surface atoms are expelled from a bombarded target due to the cascade intersecting the surface, scales as 1/U, where U is the surface binding energy. With metals, U is normally identified with the heat of atomization, °Ha, but (provided the surface is undisturbed) it is more correct to equate it either to the sum Efs+°Ha, where Efs is the surface-vacancy formation energy, or to a somewhat larger quantity. With oxides and halides, U is normally identified either with the average heat of atomization, <°Ha>, or with related quantities. A more careful definition, again restricted to undisturbed surfaces, considers the formation of isolated surface vacancies together with electronic defects, the various energies being known for a limited number of systems on the basis of contemporary point-defect theory. A typical result is that for Al2O3: UAl∼UAl+∼30 eV, U0=12 eV, UAIO∼18 eV. Such numbers account for various experimental trends, including with total yields, with partial metal-atom yields, with partial MO diatomic yields, and with preferential loss of O. © 1986 Elsevier Science Publishers B. V. (North-Holland Physics Publishing Division).