Characterisation of thin films of bismuth oxide by X-ray photoelectron spectroscopy

The XPS (or ESCA) technique has been used for the characterisation of vacuum-deposited thin films of bismuth oxide. The spectra of Bi metal and Bi₂O₃ powder are used for comparison. The characterisation is carried out by consideration of the positions of the Bi 4f_{$\text{7}\text{2}$} and 4f_{$\text{5}\text{2}$} peaks and by using peak-fitting routines. A lower suboxide of bismuth, and metallic bismuth are observed in bismuth oxide films as evaporated. Oxidation of these films by heating in air results in bismuth(III) oxide. A linear relation is found between the binding energies and oxidation state. The corresponding O 1s spectra for the two types of film are also discussed.