Contribution of low-energy ion bombardment to the growth of atomically flat Ag(111) and Au(111) films by glow discharge sputtering

Atomically flat Ag(111) and Au(111) films grow relatively easily by simple DC glow-discharge sputtering. A series of sputter deposition experiments on deliberately DC-biased samples illuminated the important contribution of low-energy ion bombardment leading to the superior surface flatness of the sputtered films. Smoothest films grew at around the floating potential, where the Ar+ ions impinge upon the growing film surface with maximum allowed kinetic energies of several electron volts and with an ion flux comparable to that of incoming metal atoms. It is proposed that such a low-energy ion bombardment leads to a substantial enhancement of the interlayer mass transport across the step edges on atomically terraced surfaces.