Abstract
Electron diffraction work has been carried out on yttrium films prepared in a vacuum of 5*10-7 Torr during evaporation. The crystal structure of thin yttrium films (300 AA thick or less) is mainly face-centred-cubic with a0=5.25+or-0.05 AA which can be attributed to cubic yttrium dihydride. The amount of the FCC phase decreases with increasing film thickness and films about 600 AA thick are mainly HCP alpha yttrium. When air and hydrogen are admitted to the system, the films react to form oxide and hydride respectively. The time dependence of the electrical resistance of these films has been studied and it is found that in the case of hydrogen contamination there is a minimum in the resistance-time curve. Electron diffraction observations have also been made. All the films transform to Y2O3 when heated in an intense electron beam inside the electron microscope. The resistivity results are discussed in terms of the known electrical resistivities of compounds of yttrium.