Preparation of iron selenide films by selenization technique

Abstract

Iron selenide films have been grown by selenization of evaporated iron thin films. The substrates temperature during selenization was 573 or 723 K. It is shown that whatever the substrate temperature is, for a partial pressure of Se of 3.75×10 −2 Pa, there is selenide compound formation. It is shown that the films are mainly composed of tetragonal FeSe while some crystallites of orthorhombic FeSe 2 are also present. XPS shows that before etching there is some superficial selenium excess while some oxidation of Fe and Se is put in evidence at the surface of the films. However, after etching the superficial oxidation disappears. After annealing for 2 h at 773 K under vacuum the films become crystallized in the hexagonal structure of FeSe, while no FeSe 2 is detected. The Se/Fe ratio tends towards 1. When annealed in the same conditions, but in selenium atmosphere, the films obtained are FeSe 2 films.