Atomistic simulation of the vapor deposition of Ni/Cu/Ni multilayers: Incident adatom angle effects

Abstract

Molecular dynamics simulations have been used to explore the effects of incident adatom angle upon the atomic scale structure of Ni/Cu/Ni multilayers grown by vapor deposition under controlled incident atom energy conditions. For incident atom energies of 1 eV or less, increasing the incident angle increased interfacial roughness, resulted in void formation in the nickel layer, and intermixing at the interfaces between metal layers. The interfacial roughness that formed during low impact energy oblique angle deposition was significantly reduced by substrate rotation during growth. However, rotation had no beneficial effects upon interfacial mixing. The use of a higher incident atom energy (⩾5 eV/atom) resulted in flatter interfaces and eliminated voids under oblique incidence conditions, but it also caused more severe interfacial mixing by an atomic exchange mechanism. When low (thermal) impact energies were used to deposit the first few monolayers of each new metal layer, intermixing by the exchange mechanism during subsequent hyperthermal energy deposition could be significantly reduced. Using this modulated incident energy growth strategy, films with little interfacial roughness and intermixing could be grown over a wide range of incident angles with or without substrate rotation.