Localized Charging Effects Resulting From Focused Ion Beam Processing Of Non- Conductive Materials
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Localized Charging Effects Resulting From Focused Ion Beam Processing Of NonConductive Materials Marion.A. Stevens-Kalceff,1 S. Rubanov1 and P. R. Munroe2 1
School of Physics, University of New South Wales, Sydney, 2052, NSW, Australia. School of Materials Science and Engineering, University of New South Wales, Sydney, 2052, NSW, Australia. 2
ABSTRACT Focused Ion Beam (FIB) systems employ a finely focussed beam of positively charged ions to process materials. Ion induced charging effects in non-conductive materials have been confirmed using Scanning Surface Potential Microscopy (SSPM). Significant localized residual charging is observed within the ion implanted micro-volumes of non-conductive materials both prior to and following the onset of sputtering. Characteristic observed surface potentials associated with the resultant charging have been modelled, giving insight into the charging processes during implantation and sputtering. The results of this work have implications for the processing and microanalysis of non-conductive materials in FIB systems. INTRODUCTION Charged beam irradiation of poorly conducting materials may result in the trapping of charge within the irradiated specimen. Irradiation induced charging in an electron microscope with a focused electron beam is known to result in (micro-) modification of poorly conducting specimens [1-3]. The possibility of focused ion beam induced localized specimen charging must also be considered. Ion induced charging effects in electrically insulating materials have been investigated using Scanning Surface Potential Microscopy (SSPM) which is also known as Kelvin Probe Microscopy (KPM). Scanning Probe Microscopy (SPM) techniques enable nondestructive three dimensional high spatial resolution real space images of surfaces via detection of local interactions between the specimen surface and a sharp probe [4]. Surface Potential Microscopy is a specialized Atomic Force Microscopy technique in which long-range Coulomb forces between a conductive atomic force probe and a specimen enable the electrical potential at the specimen surface to be imaged with high spatial resolution. Surface Potential Microscopy has been used to characterize non-conductive materials exposed to gallium ion (Ga+) irradiation in a Focused Ion Beam system. Ion beam irradiation of poorly conducting materials may result in the trapping of charge at either pre-existing or ion irradiation induced defects, thereby inducing a localized electric field within the irradiated/ implanted specimen. Significant localized residual charging is observed within the gallium implanted micro-volumes of non-conductive materials both prior to and following the onset of sputtering. The reproducible characteristic observed surface potentials associated with the trapped charge are compared with calculated potential profiles. This gives insight into charging processes during implantation and milling and the resultant spatial distributions of the residual trapped charge.
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EXPERIMENTAL DETAILS FIB system
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