Intensity of Diffraction of Electrons by ZnO

Electron diffraction patterns of ZnO powder have been obtained in the range from 10 to 80 kv by using two types of camera. The intensity distribution has been determined photographically and shows marked deviations from the intensity distribution of the corresponding x-ray pattern. It has been shown that these deviations are not due to impurities, difference in structure due to methods of preparation, coincidences with another form of ZnO, or due to preferred orientation. The scattering as a function of sin () is discussed on the basis of additional surface reflection, dynamic reflection and refraction of the electrons, and it is found that also these effects cannot account for the anomalous intensity distribution. Complete agreement between experimental and calculated curves for the scattering factor is obtained by assuming a distortion of the electron cloud (M shell of the zinc and L shell of oxygen) resulting in a different parameter for the distance Zn nucleus---oxygen nucleus, and Zn electrons-oxygen electrons. The resulting structure factor has the form S=Z (Zn) -F₍, ₋ (Zn) e^2{a₍, e^l}+Z (O) e^2-F₍, ₋ (O) e^2{ (q+{b₍, e) }^l}.