ELECTRON-DIFFRACTION FROM GRATINGS FABRICATED BY ELECTRON-BEAM NANOLITHOGRAPHY

The ability to produce nanometre-scale features in certain inorganic f ilms offers the possibility of phase manipulation of electron waves. G ratings consisting of a square array of 100 x 100 holes with a spacing as low as 10 nm were drilled in thin films of AlF3 using the 0.5 nm e lectron probe of a VG HB501 scanning transmission electron microscope (STEM). The sample thickness was chosen so that its inner potential wo uld change the phase of a 200 keV transmitted electron wave by approxi mately 2 pi with respect to a reference wave through a complete hole. Both constant phase and graded phase gratings have been produced. Elec tron diffraction patterns from these nanostructures have been observed in a JEOL 2000EX TEM at 200 keV. Simple computer simulations were use d to aid the interpretation of the diffraction patterns. The graded ph ase gratings demonstrate conclusively that the phase of the diffracted electron wave can be manipulated by exploiting the effect of the inne r potential.