Intrinsic and defect related luminescence in double oxide films of Al–Hf–O system under soft X-ray and VUV excitation

Abstract

Cite this article as: V.A. Pustovarov, Т.P. Smirnova, M.S. Lebedev, V.A. Gritsenko and M. Kirm, Intrinsic and defect related luminescence in double oxide films of Al-Hf-O system under soft X-ray and VUV excitation, Journal of Luminescence, http://dx.doi.org/10. 1016/j.jlumin.2015.10.053 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Hafnia films and films mixed with alumina were grown in a flow-type chemical vapor deposition reactor with argon as a carrier gas. In addition, pure alumina films were prepared by the atomic layer deposition method. A strong emission band with the peak position at 4.4 eV and with the decay time in the μs-range was revealed for pure hafnia films. The emission peak at 7.74 eV with short nanosecond decay kinetics was observed in the luminescence spectra for pure alumina films. These emission bands were ascribed to the radiative decay of self-trapped excitons (an intrinsic luminescence) in pure HfO 2 and Al 2 O 3 films, respectively.Along with intrinsic host emission, defect related luminescence bands with a larger Stokes shift were observed. In the emission spectra of the solid solution films (x= 4; 17; 20 at.%) the intrinsic emission bands are quenched and only the luminescence of defects (an anion vacancies) was observed. Based on transformation of the luminescence spectra and nsluminescence decay kinetics, as well as changes in the time-resolved luminescence and 2 luminescence excitation spectra, the relaxation processes in the films of solid solution are discussed.

The Bright X‐Ray Stimulated Luminescence of HfO2 Nanocrystals Activated by Ti Ions

“…Spectroscopic investigations and computational calculations by DFT have evidenced that oxygen vacancies play a major role as defect centers responsible for the optical emissions in hafnia. In fact, different variants of oxygen vacancies have been related to additional electronic levels within the bandgap of HfO 2 . Nevertheless, in nominally pure HfO 2 NPs, the intrinsic defect‐related band centered at around 2.50 eV overlaps with the blue emission due to accidental Ti impurities in the matrix.…”

Oxygen Vacancy in Hafnia as a Blue Luminescence Center and a Trap of Charge Carriers

“…29 The band at 4.4 eV was observed in both single crystals and films of HfO 2 and is interpreted as autolocalized excitons luminescence. 30,31 The PL and PLE spectra for HfO x⩽2 and HfO 1.83 are shown in Figures 3a, b. Under the HfO x⩽2 excitation with quantum energy 5.25 eV, there are two PL bands observed with peak energies of about 2.7 and 3.7 eV.…”

Luminescence of Hf-=SUB=-x-=/SUB=-Zr-=SUB=-1-x-=/SUB=-O-=SUB=-2-=/SUB=- thin films upon excitation with vacuum ultraviolet synchrotron radiation

“…Indeed, as was shown even earlier, under such an SRexcitation in the PL spectra of the most perfect films based on HfO 2 , ZrO 2 obtained by the plasma atomic layer deposition (ALD), a band in the region 4.2−4.4 eV, corresponding to the emission of selftrapped excitons (STE) [7,8], is clearly manifested. It is noted that as the defect concentration increases, the STE PL yield decreases, but the emission band increases in the region 2.7−3.1 eV, which is associated with defects in the crystal structure [9].…”