The assessment of microscopic charging effects induced by focused electron and ion beam irradiation of dielectrics.
Energetic beams of electrons and ions are widely used to probe the microscopic properties of materials. Irradiation with charged beams in scanning electron microscopes (SEM) and focused ion beam (FIB) systems may result in the trapping of charge at irradiation induced or pre-existing defects within the implanted microvolume of the dielectric material. The significant perturbing influence on dielectric materials of both electron and (Ga(+)) ion beam irradiation is assessed using scanning probe microscopy (SPM) techniques. Kelvin Probe Microscopy (KPM) is an advanced SPM technique in which long-range Coulomb forces between a conductive atomic force probe and the silicon dioxide specimen enable the potential at the specimen surface to be characterized with high spatial resolution. KPM reveals characteristic significant localized potentials in both electron and ion implanted dielectrics. The potentials are observed despite charge mitigation strategies including prior coating of the dielectric specimen with a layer of thin grounded conductive material. Both electron- and ion-induced charging effects are influenced by a delicate balance of a number of different dynamic processes including charge-trapping and secondary electron emission. In the case of ion beam induced charging, the additional influence of ion implantation and nonstoichiometric sputtering from compounds is also important. The presence of a localized potential will result in the electromigration of mobile charged defect species within the irradiated volume of the dielectric specimen. This electromigration may result in local modification of the chemical composition of the irradiated dielectric. The implications of charging induced effects must be considered during the microanalysis and processing of dielectric materials using electron and ion beam techniques.
Stevens-Kalceff
Marion A
MA
Electron Microscope Unit, University of New South Wales, Sydney, New South Wales, Australia. marion.stevens-kalceff@unsw.edu.au
Levick
Katie J
KJ
D004577:Electron Probe Microanalysis / Q000379:methods; D018625:Microscopy, Atomic Force / Q000379:methods; D008855:Microscopy, Electron, Scanning / Q000379:methods; D020527:Microscopy, Scanning Probe / Q000379:methods*; D036103:Nanotechnology / Q000379:methods*