Energy Effects on Morphological Development

Many deposition techniques involve delivering the deposition flux at thermal energies that are generally less than 0.1eV. It was first recognized by Mattox(1963) that extra energy added to the surface in the form of energetic atomic fluxes improved film properties. An energetic deposition flux can greatly influence the mode of film growth, film density, adhesion, stress, crystal structure, and orientation.
The effects of collisions of energetic atoms with materials including ballistic collisions, ion mixing, and thermally stimulated exchange mixing produce effects similar to raising T_h of the substrate.Energy-stimulated atomic motion on film properties, such as reduced film stress, and change in crystal structure and preferred orientation are a secondary result of the fundamental atomic movements.
Molecular-dynamics (M-D) studies of the initial stages of thin-film growth have been shown to be particularly useful in understanding the effects of higher energy fluxes. In 1992, Gilmore and Sprague examined the effect of depositing Ag on Ag at 300K at energies of 0.1, 1, 10, 20 and 40 eV. Three monolayers consisting of 500 atoms were deposited at 0.5 and 1.0 ps intervals. Results showed that while the film growth was epitaxial at all energies, the morphology changed from island growth at 0.1 and 1 eV to layer by layer growth at 10, 20 and 40 eV.
The first conclusion is that changing the energy of the atom flux has a similar effect to increasing the temperature--namely, producing a more dense, homogeneous structure.
Another result is that there was little or no mixing of the substrate with the film atoms at 0.1, 1, and 10 eV, but for the 20 and 40 eV energies, some substrate atoms were found in the film and some film atoms were found in the substrate, with more atoms mixed with increasing energy.

Average energy per deposited atom (eV):
TE & CVD: 0.1 eV~1 eV
PLD: 1 eV ~ 10 eV