Phase Transformation of Thin Caesium Chloride Layers

Abstract

IN connexion with investigations on the structural properties of thin ionic crystal layers, the phase transformation of caesium chloride was examined by means of electron diffraction. The specimens (Merck p.a.) were prepared in a Balzers 350-G vacuum device at 2 × 10⁻⁵ torr by evaporation from a molybdenum boat, and then investigated in a hot-stage electron diffraction specimen holder of a Hitachi HU-10A electron microscope operated at 75 kV. In order to prevent sublimation during heating the caesium chloride crystal layers were coated, in the vacuum evaporator, with a thin carbon film. The contrast of the diffraction patterns was only slightly affected by this procedure. The layer thicknesses expected¹ were 20 Å and 300 Å, respectively. The Lλ values (L is the tube length and λ is the electron wave-length) were determined with a thallium chloride standard².