Self-trapped exciton and core-valence luminescence in BaF2 nanoparticles

Abstract

The influence of the BaF 2 nanoparticle size on the intensity of the self-trapped exciton luminescence and the radiative core-valence transitions is studied by the luminescence spectroscopy methods using synchrotron radiation. The decrease of the self-trapped exciton emission intensity at energies of exciting photons in the range of optical exciton creation (h E g ) is less sensitive to the reduction of the nanoparticle sizes than in the case of band-to-band excitation, where excitons are formed by the recombination way. The intensity of the core-valence luminescence shows considerably weaker dependence on the nanoparticle sizes in comparison with the intensity of self-trapped exciton luminescence. The revealed regularities are explained by considering the relationship between nanoparticle size and photoelectron or photohole thermalization length as well as the size of electronic excitations. V C 2013 AIP Publishing LLC. [http://dx.

Particle size effects on structural and optical properties of BaF2 nanoparticles

“…Luminescence studies in nanoparticles of uoride materials have shown that luminescence properties like excitation and emission quantum efficiency depend on the particle size. 14,36 Based on density functional theory calculations (DFT), Schmalzl showed that in BaF 2 , the band gap energy may shi due to structural changes in the crystal lattice parameters. 2 From these affirmations, we investigated, using measurements in the VUV region, the luminescence and excitation luminescence spectra of BaF 2 nanoparticles with different particle sizes produced using different hydrothermal treatment times.…”

“…This behavior was also predicted for BaF 2 (ref. 14) and CaF 2 (ref. 36) nanoparticles, respectively.…”

“…13 Recent studies have shown that the luminescence intensity emission and STE creation on BaF 2 NPs exhibit a dependence on particle size. 14 This paper is dedicated to studying the effect of particle size on the lattice parameter, microstrain (3), optical band gap energy (E g ) and self-trapped exciton energy (STE) of BaF 2 nanoparticles. The results are compared to literature data, showing good agreement for the optical band gap measurements.…”

Luminescence of SrF2-Ce nanoparticles under optical and X-ray excitation

“…Якщо розмiр наночастинок а менший за довжину термалiзацiї електронiв l e,th (а < l e,th ), то вiльнi електрони можуть безвипромiнювально рекомбiнувати на поверхневих дефектах або вилiтати за межi наночастинки i не брати участi в люмiнесцентних процесах усерединi наночастинки. За таких умов рекомбiнацiйна люмiнесценцiя буде iстотно гаситися [1,2,6,21], що i спостерiгається у випадку SrF 2 -Ce (а = 20 нм).…”

“…Виявилось, що розмiрний фактор є ключовим для пояснення залежностi параметрiв рекомбiнацiйної люмiнесценцiї вiд розмiрiв наночастинок. Для локалiзованих екситонiв у фторидних наночастинках продемонстровано, що суттєвим є спiввiдношення довжини термалiзацiї електрона та розмiрiв наночастинок [1][2][3][4]. Зокрема, дослiдження екситонної люмiнесценцiї SrF 2 показало, що її iнтенсивнiсть суттєво залежить вiд мiґрацiї екситонiв до поверхнi наночастинок, а також вiд спiввiдношення мiж довжиною термалiзацiї l th електронних збуджень та розмiрами а наночастинок.…”