Photoluminescence study of the electronic structure of HfO2 films

Abstract

A method was developed for investigating hafnium dioxide films; this procedure uses a hydrogen-deuterium lamp as a source of photoluminescence (PL) excitation. Photoluminescence in HfO2 films was investigated. An analysis of the PL spectra of the films showed that they coincided with the spectra described in the literature and recorded using more powerful sources (synchrotron radiation or ArF laser). A comparison of our results with the literature data confirmed that the PL spectra of the films weakly depended on the type of the substrate used for the synthesis. The PL band intensity depends on the synthetic conditions and the annealing temperature. We analyzed the PL and excitation spectra and revealed an emission band at an energy E ∼ 4 eV with a narrow excitation maximum at Emax ≅ 4.25 eV, which was assigned to the vibronic resonance transition A2Σ+ ↔ X2Πi in the OH•* excited radical. Water was detected in the PL spectra of the HfO2 films; it is trapped as an impurity after thermal decomposition of Hf(dpm)4 in the course of film growth. The detection of water in the PL spectra of these films provides new insight into the problem of the effect of this impurity on the leakage currents and the importance of control over its content in the films.