Abstract: A method and device for preparing a specimen of material for examination by a particle-optical microscope apparatus such as a high-resolution electron microscope (HREM). The known ion milling technique enables specimens to be made sufficiently thin so as to be electron-transparent, that being a condition for HREM materials examination. However, that results in amorphous material on the surface of the specimen which may cause blurring of the image of the surface and also lead to incorrect materials analysis. In accordance with the invention, the surface of the specimen is subjected, possibly following ion milling, to ion bombardment from a plasma of ionized gas which is formed adjoining such surface. This achieves ion etching of the surface, and consequent reduction of the thickness of the specimen, without formation of disturbing amorphous regions on the surface.