DOES PHONON-SCATTERING GIVE HIGH-RESOLUTION IMAGES

Electron interaction with atoms in a solid, creating or destroying phonons, gives rise to more scattering at higher angles than does purely elastic scattering. It would seem that atoms would appear smaller in real space, and images generated from phonon-scattered electrons would show sharper contrast. The theory for the distribution of phonon scattering in diffraction patterns has been extended to describe high-resolution imaging. It is shown that if it were possible to form an image involving only one phonon of a given wave vector, then a sharper contrast image could be formed. As the phonon scattering distribution is peaked away from the origin of reciprocal space strong ''half-period'' fringes would be observed. Summing over all possible phonon scattering accepted by the objective aperture severely attenuates any sharper contrast features. Calculations show that the degree of attenuation is strongly dependent on the phonon dispersion relation and is particularly significant for a constant frequency, Einstein, phonon dispersion.