Energy dissipation of highly charged ions on Al oxide films

Abstract

Slow highly charged ions (HCIs) carry a large amount of potential energy that can bedissipated within femtoseconds upon interaction with a surface. HCI–insulator collisionsresult in high sputter yields and surface nanofeature creation due to strong couplingbetween the solid’s electronic system and lattice. For HCIs interacting with Al oxide,combined experiments and theory indicate that defect mediated desorption can explainreasonably well preferential O atom removal and an observed threshold for sputtering dueto potential energy. These studies have relied on measuring mass loss on the targetsubstrate or probing craters left after desorption. Our approach is to extracthighly charged ions onto the Al oxide barriers of metal–insulator–metal tunneljunctions and measure the increased conductance in a finished device after theirradiated interface is buried under the top metal layer. Such transport measurementsconstrain dynamic surface processes and provide large sets of statistics concerningthe way individual HCI projectiles dissipate their potential energy. Results forXeq + forq = 32, 40, 44 extracted onto Al oxide films are discussed in terms of postirradiationelectrical device characteristics. Future work will elucidate the relationship betweenpotential energy dissipation and tunneling phenomena through HCI modified oxides.