HICS: Highly charged ion collisions with surfaces
Abstract The layout of a new instrument designed to study the interaction of highly charged ions with surfaces, which consists of an ion source, a beamline including charge separation and a target chamber, is presented here. By varying the charge state and impact velocity of the projectiles separately, the dissipation of potential and kinetic energy at or below the surface can be studied independently. The target chamber offers the use of tunable metal–insulator–metal devices as detectors for internal electronic excitation, a time-of-flight system to study the impact induced particle emission and the possibility to transfer samples in situ to an ultra high vacuum (UHV) scanning probe microscope. Samples and detectors can be prepared in situ as well. As a first example data on graphene layers on SrTiO3 which have been irradiated with Xe36+ are presented.
Fabrication of nanopores in 1 nm thick carbon nanomembranes with slow highly charged ions
We describe the use of slow highly charged ions as a simple tool for the fabrication of nanopores with well-defined diameters typically between 10 and 20 nm in freestanding, 1 nm thick carbon nanomembranes (CNMs). When CNMs are exposed to a flux of highly charged ions, for example Xe40+, each individual ion creates a circular nanopore, the size of which depends on the kinetic and potential energy of the impinging ion. The controlled fabrication of nanopores with a uniform size opens a path for the application of CNM based filters in nanobiotechnology.
Charge exchange at molecular-orbital pseudocrossings as an important mechanism for nonkinetic-electron emission in slow-multicharged-ion (v
Kinetic energy distributions of electrons emitted in the interaction of slow (10q-keV) multicharged ions (N,O,Ne,Ar) with metal surfaces (Cu,Au) are presented. We observe secondary-electron emission, quasielastic-scattering processes, and, superimposed upon this, one-center Auger decay of both projectile and target vacancies. Two classes of target Auger-decay features are observed. Long-lived target vacancies decay, leading to discrete Auger line features, similar to those arising from electron-impact excitation. Short-lived target vacancies appear to decay in the field of the projectile, leading to broadened Auger line features. Observation of the decay of target vacancies, and their correlation with the presence of particular projectile vacancies, shows that a measurable fraction of projectile vacancies survive until small-impact-parameter collisions with surface or subsurface atoms. The data imply that projectile neutralization proceeds via two channels, viz., capture of valence-band electrons to projectile excited states, followed by one-center Auger decay, and at pseudocrossings of molecular orbitals correlating with discrete inner-shell levels of the target and projectile.