Electron Beam Induced Crystallisation in Iron (III) Fluoride

Metal fluorides are excellent candidates as high resolution inorganic resists in electron beam nanolithography. Hence it is important to study their damage characteristics under the electron beam to understand their behaviour as inorganic resists. In this paper the electron beam induced damage process in amorphous FeF3 films deposited by different techniques is investigated using selected area diffraction patterns and time resolved parallel electron energy loss spectroscopy. It is found that fluorine is lost from amorphous FeF3 during irradiation and that the material crystallises mainly to FeF2 with some crystalline FeF3. Time resolved energy loss spectroscopy studies show that the coordination polyhedra in amorphous FeF3 are randomly arranged FeF6 octahedra which arrange themselves to give a long range order in the electron beam during crystallisation to FeF2 and FeF3.