Photoluminescence of sol–gel-prepared hafnia

We employed a sol–gel route followed by a thermal treatment (up to 1000 °C) to prepare crystalline (monoclinic) hafnium dioxide. Thorough steady-state and time-resolved photoluminescence characterization of the material within the temperature range of 10–300 K was conducted by using various excitation sources. The most prominent spectroscopic feature of the material was an intense broad emission band centered at 2.3–2.5 eV with an associated excitation band centered at 4.2–4.4 eV (well below the bandgap of monoclinic hafnia). The emission was characterized by an essentially non-exponential, thermally stimulated decay and exposed a marked blue shift with the increase of temperature from 10 to 300 K. Relation of the emission to the intrinsic defects of hafnia is discussed.