X-ray absorption spectroscopy study on oxygen-deficient hafnium oxide film

We investigated the influence of oxygen vacancy on the electronic and atomic distributions in hafnium oxide, using hard and soft x-ray absorption spectroscopies. Analyses on the Hf L₃-edge extended x-ray absorption fine structures revealed that the average Hf-O bond length reduces more than -0.1 Å in the presence of oxygen vacancy, consequently on the lattice relaxation. Furthermore, the O K-edge absorption spectrum shows additional band tail state beneath the genuine Hf 5d conduction band, which manifests a small occupation in Hf d shell in the oxygen-deficient oxide. However, the nonzero d occupation is found not to involve a ferromagnetic spin correlation by the absence of features in the Hf N₃-edge magnetic circular dichroism.