A new approach to nuclear microscopy: the ion–electron emission microscope

Abstract

A new multidimensional high lateral resolution ion beam analysis technique, Ion-Electron Emission Microscopy or IEEM is described. Using MeV energy ions, IEEM is shown to be capable of Ion Beam Induced Charge Collection (IBICC) measurements in semiconductors. IEEM should also be capable of microscopically and multidimensionally mapping the surface and bulk composition of solids. As such, IIEM has nearly identical capabilities as traditional nuclear microprobe analysis, with the advantage that the ion beam doeszot have to be focused. The technique is based on determining the position where an individual ion enters the surface of the sample by projection secondary electron emission microscopy. The x-y origination point of a secondary electron, and hence the impact coordinates of the corresponding incident ion, is recorded with a position sensitive detector connected to a standard photoemission electron microscope (PEEM). These signals are then used to establish coincidence with IBICC, atomic, or nuclear reaction induced ion beam analysis signals simultaneously caused by the incident ion.

Nuclear emission microscopies

“…This unity detected event probability guarantees that this type of analysis minimizes the amount of radiation darnage to the sample. This is not necessarily the case with the Nuclear Emission Microscopy method, as has been discussed previously [1].…”

“…2b and reference [1], with IEEM a beam of MeV ions, provided by an accelerator, impinges on a semiconductor sample (currently at an angle of 75°with the surface normal) which is usually coated with a thin metal layer to enhance production of particles, which in this case are secondary electrons. The secondary electrons which are generated by each ion (and shown to originate at X,Y in Fig.…”

“…1 . In [1] we measured the total system detection efficiency to be 0.05 using protons on Aucoated PIN diodes using the largest aperture in the PEEM (300 urn). This indicates that for a PSD efficiency of S=0.5, that E=O.1, and these values are also listed in the table.…”

“…A radicall y new form of nuclear microscopy, Nuclear Emission Microscopy (NEM), was invented by Sandia two years ago to address the problem of performing single-ion Nuclear Microprobe Analysis (NMA) using ions that are difficult, or even impossible, to focus with conventional nuclear microprobe [1]. The basic premise of NEM is that it is sometimes easier to determine where an unfocused ion hits a sample rather than focus and scan an ion to a prespecified location.…”

“…The first NEM was called Ion Electron Emission Microscopy or IEEM [1]. With IEEM, the ion beam is not focused, but instead, the secondary electrons made by each ion on the target are project imaged through a set of electrostatic lenses onto a single electron position sensitive detector (PSD).…”