Observation of the ion-mirror effect during microscopy of insulating materials

Utilizing the ion beam of a focused ion beam (FIB)/scanning electron microscope (SEM) microscope to investigate non-conductive samples, we observe a mirror image very much similar to the one that is commonly obtained with the electron beam and the same samples. To our knowledge this is the first observation of what can be called 'Ion-Mirror Effect'. This effect is produced by a positive charging of the sample obtained by rastering with high-energy ions (30 kV) and a subsequent imaging with low energy ones (5 kV). The proposed explanation is that first a positive charge is trapped within the sample and eventually the lower energy ions are deflected back by the latter, and hit the surface of the microscope chamber very similar to what happens in the 'Electron-Mirror Effect'. The mirror image is produced after detection of the electrons produced by the interaction between ions and the chamber materials.