Phase plate for a TEM

A phase plate suitable for an electron microscope, the microscope adapted to generate a beam of electrons, said beam of electrons in working passing through a sample, said beam of electrons in working, after passing through the sample, divided in an undiffracted beam and a diffracted beam, the sample in working imaged in an image plane where the undiffracted and the diffracted beams in working interfere to form an image, the phase plate placed in a plane where the undiffracted and the diffracted beam in working are focused, the phase plate comprising:

• a central area, said central area in working causing a first phase shift of electrons,
• a first thin film surrounding and bordering the central area, said first thin film in working causing a second phase shift of electrons differing from the first phase shift,
• a holder structure surrounding the first thin film suitable for holding the phase plate, the difference between first phase shift and second phase shift in working causing an improvement of the contrast in the image for a range of spatial frequencies, wherein
• between the first thin film and the holder structure at least one further thin film is present, said further thin film in working causing a further phase shift of electrons differing from the second phase shift, the difference between first phase shift and further phase shift for a further range of spatial frequencies in working causing an improvement of the contrast in the image compared to the situation where the further phase shift would equal the second phase shift
• the first thin film and the further thin film are formed as concentric annuli, the annulus forming the further thin film surrounding and bordering the annulus forming the first thin film, the centre of the annuli coinciding with the middle of the central area.