Atomic assembly of metal surfaces and interfaces

Low-energy ion-assisted control of interfacial structures in metallic multilayers

“…The predicted misfit dislocation structures are also similar to those observed by high-resolution transmission electron microscopy [31,32]. Recent simulations of ion interactions with a model Co-on-Cu bilayer system indicate that low (5-10 eV) energy impacts can be highly effective at flattening small (10 atoms) cobalt clusters on (1 1 1) copper surfaces without inducing interfacial alloying [24,33,34]. They also reveal that appropriate combinations of ion species (mass), ion energy, ion fluence, and ion incident angle can be used to selectively activate either atom recoil, atomic exchange, or direct jumping mechanisms to flatten surface asperities [24,33].…”

“…Nonetheless, the simulated conditions were carefully chosen to ensure that the time interval between ion or adatom arrival was at least 0.15 ps or above. This time interval allows the impact-induced surface reconstructions to be realistically captured and should allow the effects of assisting ions to be accurately predicted [24,33]. The study was restricted to argon ion effects since it is the most commonly used inert gas in ion-assisted vapor deposition experiments.…”

“…Recent simulations of ion interactions with a model Co-on-Cu bilayer system indicate that low (5-10 eV) energy impacts can be highly effective at flattening small (10 atoms) cobalt clusters on (1 1 1) copper surfaces without inducing interfacial alloying [24,33,34]. They also reveal that appropriate combinations of ion species (mass), ion energy, ion fluence, and ion incident angle can be used to selectively activate either atom recoil, atomic exchange, or direct jumping mechanisms to flatten surface asperities [24,33]. These studies further indicate that nearly perfect multilayer structures can be vapor deposited using ion assistance if the ion energy is maintained between the critical energies for flattening and intermixing.…”

“…These energies and the energy gap depend on the ion incident angle and ion mass. The widest critical energy gap is achieved for an ion incident angle around 501 from surface normal (which avoids easy atom penetration in crystal channeling directions) using an ion mass comparable to that of the metals [33].…”

Structural and Material Exploration of Magnetic Tunnel Junctions

“…Low energy IBD would improve the uniformity of the film thickness and reduce interlayer mixing but requires a large target to avoid overspill sputtering. Previous simulation studies [40][41][42] Instead of using a conventional grid ion beam source, the BTIBD applies two novel low energy ion sources that combine an end-Hall ion source [44] and a hollow cathode electron source [45]. The advantage of this combined source over conventional IBD source is that it can provide a very high density of inert gas ions with very low energy (several eV) [39].…”