Violet–blue luminescence from hafnium oxide layers doped with CeCl₃ prepared by the spray pyrolysis process

Abstract

HfO2:CeCl3 coatings were deposited by the spray pyrolysis method employing hafnium dichloride oxide and CeCl3 dissolved in deionized water (18 MΩ/cm). The room temperature photoluminescence characteristics of the HfO2:CeCl3 films were studied as a function of the deposition parameters such as doping concentrations and substrate temperature. The presence of two different Ce3+ centres in HfO2 is detected from photoluminescence measurements. A reduction of the luminescence intensity is observed with an increase of both the CeCl3 concentration and the deposition temperature. X‐ray diffraction measurements of these films showed that the crystalline structure depends on the substrate temperature. For substrate temperatures less than 350 °C the deposited films are almost amorphous, while substrate temperatures higher than 400 °C produce diffraction peaks corresponding to the monoclinic phase of HfO2. The chemical composition of the films as determined by energy dispersive spectroscopy is also reported. Furthermore, the surface morphology characteristics of the coatings, as a function of the deposition temperature, are also presented. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Blue-yellow photoluminescence from Ce3+→Dy3+ energy transfer in HfO2:Ce3+:Dy3+ films deposited by ultrasonic spray pyrolysis

“…The excitation spectrum monitored at 575 nm (inside the 4 F 9/2 → 6 H 13/2 emission transition of Dy 3+ ) exhibits, in addition to the ( 6 H 15/2 → 4 K 17/2 , 4 M 19/2,21/2 , 4 I 13/2 , 4 F 7/2 , 6 H 15/2 → 4 G 11/2 , 6 H 15/2 → 4 I 15/2 and 6 H 15/2 → 4 F 9/2 ) Dy 3+ absorption (excitation) transitions, a broad band in the 260-380 nm region, which is similar to the 4f → 5d Ce 3+ absorption (excitation) band observed in the excitation spectrum of a HfO 2 film doped with 1.9 at.% of Ce 3+ [22]. This excitation spectrum is shown in Fig.…”

“…4(a) shows emission spectra of the HOC, HOCD0.5, HOCD1.1, HOCD1.5 and HOCD1.9 films excited with 280 nm wavelength, within the Ce 3+ 4f → 5d absorption transition. All these spectra, which have been recorded in the same experimental conditions for comparison, exhibit the blue broad band associated with the 5d 1 → 4f 1 transition of Ce 3+ ions [22]. The emission spectra of the cerium and dysprosium codoped films exhibit, in addition to the Ce 3+ emission band, the 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 emissions of Dy 3+ .…”

“…An incorporation of chlorine ions might to be induced by the Ce 3+ and/or Dy 3+ ion substitution into Hf 4+ cations in order to preserve the electrical neutrality in the trivalent ion doped HfO 2 film [22].…”

“…HfO 2 can also be used for protective coatings due its thermal stability and hardness near to diamond in its tetragonal phase [20]. The large energy gap and low phonon frequencies of the HfO 2 [21] makes it appropriate as host material to incorporate rare earth ions, such as Ce 3+ [22], Er 3+ [23], Tb 3+ [24] and Eu 3+ [25], as well as Mn 2+ [26] and Sm 3+ [27] ions, which emit within their own energy levels.…”

Characterization of gas sensing HfO2 coatings synthesized by spray pyrolysis technique

“…Hafnium oxide (HfO 2 ) films are deposited by a variety of techniques; these include atomic layer epitaxy [1], chemical vapor deposition [2], conventional electron beam evaporation [3], ion-assisted electron beam evaporation [4], sputtering [5], and ultrasonic spray pyrolysis [6]. Ultrasonic spray pyrolysis (USP) is a processing technique used in research to prepare thin and thick films and powders.…”