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In Situ Monitoring of Pulsed Laser Annealing of Eu-Doped Oxide Thin Films

Institute of Physics of the Czech Academy of Sciences, 182 21 Prague, Czech Republic
Department of Physics and Measurements, University of Chemistry and Technology, 166 28 Prague, Czech Republic
National Institute for Laser, Plasma and Radiation Physics (INFLPR), 077125 Măgurele, Romania
Faculty of Science, Charles University, 128 40 Prague, Czech Republic
Author to whom correspondence should be addressed.
Materials 2021, 14(24), 7576;
Submission received: 4 November 2021 / Revised: 30 November 2021 / Accepted: 7 December 2021 / Published: 9 December 2021
(This article belongs to the Special Issue Structural and Optical Studies of Eu3+ Doped Materials)


Eu3+-doped oxide thin films possess a great potential for several emerging applications in optics, optoelectronics, and sensors. The applications demand maximizing Eu3+ photoluminescence response. Eu-doped ZnO, TiO2, and Lu2O3 thin films were deposited by Pulsed Laser Deposition (PLD). Pulsed UV Laser Annealing (PLA) was utilized to modify the properties of the films. In situ monitoring of the evolution of optical properties (photoluminescence and transmittance) at PLA was realized to optimize efficiently PLA conditions. The changes in optical properties were related to structural, microstructural, and surface properties characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The substantial increase of Eu3+ emission was observed for all annealed materials. PLA induces crystallization of TiO2 and Lu2O3 amorphous matrix, while in the case of already nanocrystalline ZnO, rather surface smoothening0related grains’ coalescence was observed.

1. Introduction

Eu3+-doped oxide thin films possess great potential for several emerging applications in optics, optoelectronics, and sensors, i.e., waveguides, display luminophores, imaging detectors, solar cells, and scintillators [1,2,3,4,5,6,7,8,9,10,11]. Eu3+ was the dopant of choice in relation to the previously mentioned applications due to its strong emission in the visible part of spectra centered at around 612 nm [12]. As an example of well-known Eu3 dopant host matrices we can mention semiconducting ZnO, TiO2, and dielectric Lu2O3 oxides. The Eu3+-doped thin films are fabricated by a variety of methods [1,2], e.g., ion implantation [13], plasma-enhanced chemical vapor deposition [3,4,14], electrochemical deposition [5], hydrothermal deposition [15,16], chemical bath deposition [6], spraying [17,18], sputtering [4,7,8,19,20,21], evaporation [22,23], pulsed laser deposition (PLD) [24,25,26,27], matrix-assisted pulsed laser evaporation technique (MAPLE) [28], and sol-gel [9,10,29,30,31,32,33].
Post-deposition thermal treatment is usually required to activate the Eu ions and optimize the photoluminescence (PL) response [4,8,9,13,14,16,17,19,20,21,26,28,29,30,32,33]. However, the methods used for conventional thermal annealing require heating the samples to high temperature (>700 °C) for sufficiently long times in order for thermal diffusion of the defects to occur. The high-temperature processing limits the flexibility and practical applicability of these methods toward development of various optical and electro-optical devices. To address just the main disadvantages, only heat-resistant substrates can be used, undesirable crystallization of amorphous host might also occur, and, finally, the treatment of the entire sample may be undesirable in the device production.
The utilization of Pulsed Laser Annealing (PLA) to obtain and tune optically active Eu3+-doped films may profit from numerous advantages [34,35], i.e., (if necessary) horizontally structured local-rapid laser rating, ability to achieve ultra-high temperature in local scale, better controlled vertical thermal profile, controlled thermal profile, rapid processing, possibility of remote sample processing, and easy process automation. PLA plays, therefore, an important and challenging role in the development of high-tech electronic, optoelectronic, photonics, and sensing devices.
PLA technique offers a great flexibility in the number of control parameters available, i.e., laser wavelength, fluence (FL), repetition rate (frep), number of shots, and ambient atmospheres [36,37,38]. Finding the optimal PLA conditions strongly depends on sample properties, i.e., film thickness, optical properties, and microstructure. Therefore, in order to find the optimal PLA conditions for maximizing Eu3+ PL response, a number of testing samples will be necessary. In situ monitoring of PLA can be an effective way to reach the optimal conditions accurately and fast.
In this paper, we report on in situ monitoring optical properties of Eu-doped ZnO, TiO2, and Lu2O3 thin films prepared by PLD within their processing by PLA using ArF excimer laser. Photoluminescence and optical transmittance measurement techniques were implemented. The effect of PLA on morphology, microstructure, and composition was evaluated.

2. Materials and Methods

ZnO:Eu, Lu2O3:Eu, and TiO2:Eu thin films were fabricated by PLD using Nd:YAG laser (λ = 266 nm, τ = 6 ns) and KrF laser (λ = 248 nm, τ = 20 ns). The targets were Eu2O3:ZnO (1% at. Eu), Eu2O3:Lu2O3 (3% at. Eu), and Eu2O3:TiO2 (1% at. Eu). Depositions were performed in an oxygen ambient. The vacuum chamber was pumped down to an ultimate pressure of 5.10−4 Pa. The films were grown on fused silica substrates maintained at room temperature. The distance between substrate and target was 50 mm. The deposition conditions are listed in Table 1.
PLA was performed using an ArF laser (λ = 193 nm, τ = 20 ns) Compex PRO 205 F (Coherent, Inc., Santa Clara, CA, USA). To perform PLA the laser beam was focused using converging lens on the sample at the angle of 70°. The optical properties were analyzed sequentially after each PLA pulse or burst of pulses that were fired at frep = 1 Hz. The signal for in situ PL was taken from the sample edge using an optical fiber connected to a spectrometer Horiba JY Triax iHR550 (Kyoto, Japan) equipped with LN cooled CCD Symphony. The same ArF laser was used for spectra excitation at lowered FL = 10 mJ⋅cm−2 with frep = 5 Hz. Optical transmittance was in situ probed perpendicularly using light generated by a DH 2000 source (Ocean Insight, Orlando, FL, USA) and analyzed by a spectrometer. The PLA conditions are listed in Table 1 and the experimental setup is shown in Figure 1.
The structure of the films was characterized by X-ray diffraction (XRD) using an X-Ray diffractometer (EMPYREAN, Malvern Panalytical, Malvern, UK) with Cu anode (λ = 1.5406 Å) by grazing incidence (omega = 0.85°) and Bragg–Brentano measurements at room temperature. Morphology was examined by atomic force microscopy (AFM) (Dimension Icon, Bruker, Billerica, MA, USA). Chemical composition was determined by Scanning electron microscopy-Energy-dispersive X-ray spectroscopy (SEM-EDX) (Fera 3, TESCAN, Brno, Czech Republic) and the Orbis® PC Micro-XRF spectrometer (EDAX, Ametek, Berwyn, PA, USA), Rh X-ray tube, 40 kV, polycapillary optics, a diameter of 30 µm of incident beam, and a silicon-drift detector with resolution FWHM~130 eV/Mn. The thickness measurement took place on an Alphastep IQ device (KLA-Tencor Corporation, Milpitas, CA, USA) with a scan length of 5 mm, stylus force of 5.5 mg, and scan speed of 50 µm·s−1. Each line was measured two times. The stylus diamond tip had a radius of 5 µm and an angle of 60°.

3. Results and Discussion

The deposited films of all investigated materials exhibited characteristic Eu3+ PL 5D07Fj (j = 0, 1, 2, 3, and 4) emission related to f-f transition. The observation of the PL emission confirmed that the energy transfer processes in Eu3+ excitation must take place considering excitation wavelength λ = 193 nm (6.42 eV). It can be mainly related to host absorption and marginally in case of Lu2O3:Eu also to the O2−–Eu3+ charge transfer band (CTB) [39,40]. Following hyper-sensitive electric dipole transition 5D07F2, its Stark splitting and 5D07F2/5D07F1 (magnetic dipole transition) emission ratio (asymmetry ratio), we could correlate the effect of PLA on the structural properties’ modification. It provided information related to the surrounding defects and disorder around the Eu3+ ions. The 5D07F1 transition was not considerably influenced by the surrounding of Eu3+ in the particular host. The transition 5D07F2 dominated all emission spectra from Eu3+,, suggesting the local symmetry around Eu3+ was low and deviated from an inversion center. The 5D07F0 transition was only allowed, taking into account the electric dipole selection rule, in the following 10 site symmetries: Cs, C1, Cn, and Cnv (n = 2, 3, 4, 6) [12].
The values of Eg listed in Table 2 were derived using Tauc plot—plotting (αhν)1/m against photon energy (hν), where m is a parameter related to the type of transition, m = ½, and 2 corresponds to direct allowed transition and indirect allowed transition, respectively. TiO2 in anatase phase is considered as an indirect semiconductor, where m = 2 [41] while ZnO is a direct semiconductor (m = ½) [42] and Lu2O3 is considered as a direct ultrawide band gap semiconductor (m = ½) [43]. The Eg values were obtained with error of ±0.02 eV.
As for the chemical composition of the films, Eu dopant concentrations obtained by EDX and XRF analyses corresponded to those of the targets and any substantial variation after PLA was not detected.
In the following, let us discuss the properties’ modifications of each material, Eu-doped ZnO, TiO2, and Lu2O3 by PLA, in more details.

3.1. ZnO:Eu

The evolution of optical properties (PL emission and transmittance spectra) of ZnO:Eu films with increasing number of PLA shots is shown in Figure 2 and Figure 3, respectively. Characteristic Eu3+ red emission was detected at 587.3 nm and 593.8 nm (5D07F1), 609.9 nm and 618.8 nm (5D07F2), 654.8 nm (5D07F3), and 691.5 nm, 692.8 nm and 704.4 nm (5D07F4). The spectra in Figure 2 revealed that different emitting centers related to Eu may coexist in ZnO:Eu films, which is commonplace for wide band gap materials of wurtzite structure [44]. Eu3+ ions in ZnO:Eu films generally occupy the substitutional sites of Zn2+ ions. This fact turns 5D07F1 and 5D07F2 transitions to be allowed. The observation of 5D07F2 transition splitting suggests that Eu3+ can be at a substitutional Zn site (C3v symmetry). We could not observe clear evidence of 5D07F0 transition whose appearance in PL spectra of ZnO:Eu was related with Eu3+ presence in other sites (e.g., the interstitial sites or surface/grain boundary of ZnO nanocrystals) [33,45,46]. A potential drawback of our interpretation can be the relatively low intensity of the PL signal. However, if we expect only a small fraction of Eu3+ in the sample located at ZnO nanocrystals’ surface, Eu3+ emission lines’ intensities and asymmetric ratio would increase with the increasing number of PLA shots, while the asymmetric ratio saturated at N# = 400, as it is depicted in Figure 2. The enhancement of Eu3+ PL intensity at 609.9 nm by a factor of 4.1× was obtained. The PL signal intensity and asymmetric ratio variations might be related to microstructure modification, as displayed in Figure 4, where grains coalescing took place. It was reported that the energy relaxation process of excited Eu3+ ions should play a more important role toward PL efficiency enhancement than the energy transfer process from ZnO matrix to Eu3+ ions [47].
The transmittance spectra shown in Figure 3 confirm good quality of the film because transmittance of ~80% was reached in the visible light spectrum (VIS) band. There was not noticeable any variation in transmittance spectra, which confirmed that defects like oxygen vacancies were not introduced during the PLA processing. Band gap value decreased after PLA from Eg~3.28 eV to 3.25 eV. Recently, we observed similar Eg values and trends at ZnO:Eu film PLD deposited at a substrate temperature of 300 °C [24].
AFM images of the film surface presented in Figure 4 revealed that PLA caused interconnecting of the grains accompanied by substantial lowering of surface roughness, as depicted in Table 2. We could attribute this effect to reaching the melting threshold of ZnO:Eu thin film. Similar results of UV PLA on the surface morphology of ZnO thin film of comparable thickness deposited by PLD on quartz substrate were reported at higher FL ≥ 140 mJ/cm2, where coalesced nanoclusters kept the wurtzite crystalline structure [36]. The PLA-induced coalescence of nanoparticles was also reported at ZnO [48] and ZnO:Eu [37] films of lower thickness < 60 nm on metal and Si substrates, respectively.
XRD patterns of as-deposited and PLA-treated ZnO:Eu film, shown in Figure 5, did not reveal any substantial changes in structural properties. This fact is in good correlation with our previous results dedicated to PLA of ZnO:Eu film by KrF laser [37]. The film exhibited a hexagonal wurtzite structure of fibrous texture along the c-axes with random lateral orientations of crystallites. The FWHM of the strongest (002) peak was used to estimate the average crystallite size by using the Scherrer’s formula and were ≈19 nm. This correlated with the AFM measurement data. The presence of additional phases, such as Eu2O3, was not detected. Considering the larger ionic radius of Eu2+ (1.13 Å) than Eu3+ (0.95 Å) in comparison with Zn2+ (0.74 Å), substitution of Eu3+ ions at Zn2+ sites seemed to be more favorable than that of Eu2+ ions but charge compensation must take place [24].

3.2. TiO2:Eu

The dependence of optical properties of TiO2:Eu films, i.e., PL emission and transmittance spectra, on the number of PLA shots is presented in Figure 6 and Figure 7, respectively. The transmittance spectra underline the high quality of the film because any evident absorption in VIS that can be related to defects such as oxygen vacancies and a presence of Ti suboxides did not appear [28]. We could observe a weak broadened emission line of Eu3+ for the as-grown, which is characteristic for the amorphous phase [49]. The increase of Eu3+ PL intensity accompanied by sharpening lines of split 5D07F2 transition, as depicted in Figure 6, as well as a slight increase of transmittance (1.3%) are corelated to surface modification and gradual crystallization of TiO2 matrix. The significant increase of Eu3+ PL intensity (~5×) was detected at N# = 50, where transmittance decreased and further remained constant. TiO2 nanocrystallites formed by PLA may act as sensitizers absorbing the excitation energy more efficiently [31,49]. We can recognize splitting 5D07F2 transition to peaks located at 611.1 nm, 614 nm, 616.9 nm, 624 nm, and 626.1 nm. The splitting may indicate Eu3+ located in D2 and S4 symmetry sites of TiO2 [49]. The slight decrease of Eu3+ PL intensity of 5D07F2 transitions at 616.9 nm and 624 nm after N# = 200 can be attributed to the creation of well-crystalized anatase TiO2 matrix [28,50]. Because the intensity of 5D07F1 transition was weak, it made it impossible to conclude on its splitting. The 5D07F0 transition could not be followed at all, which may exclude Eu3+ occupying C2v symmetry sites. Concerning transmittance, we must notice that its variation within PLA processing was generally rather weak. Its relative variation was less than 2%, which is slightly above the measurement error.
We did not obtain any shift in Eg value after PLA, as listed in Table 2. Similar values of Eg~3.22 eV for TiO2 material [51] and anatase-like thin TiO2 films [52] were reported. There are reports of higher Eg~3.3 eV for TiO2:Eu films deposited by the spray pyrolysis technique. Our Eg values suggested we did not introduce defects in the films since lowering Eg from 3.03 eV to 2.52 eV was observed after aerodynamic levitated laser annealing of defect-rich (oxygen vacancies) TiO2 nanoparticles [53]. Lower Eg~2.7 eV was also reported for TiO2:Eu films prepared by MAPLE, where Eg value shift was related to interstitial Eu doping [28].
An AFM image of the film surface, shown in Figure 8, revealed clear evidence of crystallization of the film after PLA, as observed by XRD. The growth of grains is reflected by the increasing roughness, as depicted in Table 2.
XRD analyses, shown in Figure 9, revealed the amorphous character of as-grown film, while the PLA-treated film exhibited polycrystalline tetragonal anatase phase TiO2, as referred in the JCPDS Card NO: 96-500-0224 file. Peak positions and reflections’ planes derived from XRD patterns were 25.38° (011), 36.78° (013), 37.68° (004), 48.03° (020), 53.68° (015), and 55.08° (121). Crystallites’ size was derived using Sherrer’s formula and was ≈ 46.1 nm. Anatase TiO2 phase was also obtained by KrF PLA of nanoparticles at FL = 34 mJ/cm2, while at a higher FL a rutile phase appeared [54]. The crystallization of divalent- or trivalent europium-containing oxide compounds or europium titanate [55] was not detected by XRD. The large mismatch in the ion radii of Eu3+ and Ti4+, 0.95 A and 0.68 A, respectively, may cause a crystal structural distortion and also make difficult the substitution of Ti4+ by Eu3+ within the anatase lattice [31].

3.3. Lu2O3:Eu

The PL emission spectra of Lu2O3:Eu film, shown in Figure 10, exhibited a strong luminescence signal of Eu3+ attributed to transition 5D07Fj (j = 0–4) as well as a lower intensity signal from transition 5D17Fj (j = 1–2). The excitation efficiency by ArF laser at λexc = 193 nm profited from Lu2O3 host lattice broad absorption band centered around λ = 210 nm [40]. Let us notice that the appearance of 5D17Fj (j = 1–2) transitions is much less common in Eu3+-doped materials. These transitions could be observed in compounds with low-lattice phonon energy, e.g., Lu−O that leads to multiphonon relaxation [12,56]. They were also reported at films grown by chemical vapor deposition (CVD) [3]. Concerning 5D07Fj (j = 0–2) transitions, the PL spectrum revealed similar features as the spectrum (excited at λexc = 254 nm) of PLD-prepared Lu2O3:Eu film with 5% Eu content [27]. Transitions were composed of peaks at 580.2 nm for 5D07F0 (Eu3+ in the noncentrosymmetric C2 site [57]); 582.2 nm, 586.7 nm, 593.1 nm, and 600.3 nm for 5D07F1 (Eu3+ in the C2 and S6 (centrosymmetric) sites [40,58]); 611.0 nm, 612.6 nm, 624 nm, and 632 nm for 5D07F2 (Eu3+ exclusively in the C2 site [40,58]); 650.2 nm and 664 nm for 5D07F3; 708 nm, 710.1 nm, and 713.5 nm for 5D07F4; 533.4 nm for 5D17F1; and 553.6 nm for 5D17F2. The most intense peak observed at 611 nm is characteristic of the cubic phase of rare earth sesquioxides [25,32,40].
We noticed the most substantial change in the film optical properties, shown in Figure 10 and Figure 11, after the first PLA shot. The most substantial increase of Eu3+ intensity emission and optical transmittance was obtained. The Eg value shifted from 5.47 eV to 5.51 eV, where the latter values corresponded to those reported for evaporated Lu2O3 films [43,59]. This may be attributed to both surface and structure modifications (as observed by AFM and XRD in Figure 12 and Figure 13, respectively). The asymmetric ratio increased from 7.9 to 9.5 reached at N# = 2, which is reflecting the site symmetry decreasing related with film structure modification. The asymmetric ratio value was then decreasing to 9 and not changing for N# = 4–7. PLA led to the maximum enhancement of 2.8 times for Eu3+ intensity emission at 611.0 nm. The energy transfer from Eu3+ residing in S6 to Eu3+ in C2 may take place because the levels of Eu3+ in the site S6 lie above those for site C2. It was reported, based on following the 5D07F1/5D07F0 ratio, that the rate of the energy transfer may change with the crystallites’ sizes (it is lower for larger crystallites) or because the location of Eu3+ in C2 site is more common for small crystallites [57,60]. We did not observe any considerable variation of this ratio within the PLA process, although the crystallites’ size varied, as confirmed by XRD.
AFM analyses, shown in Figure 12, revealed similar morphology for as-deposited and PLA-treated film with typical Sq = 3.7 nm. Slight surface smoothing was observed after PLA and Sa decreased from 2.04 nm to 1.48 nm.
A substantial improvement of the crystalline structure after PLA treatment was evidenced by XRD diffraction patterns, depicted in Figure 13. While as-deposited film was rather amorphous, the film revealed a polycrystalline structure after seven PLA shots. The estimated crystallites’ size was 10.9 nm. The similar XRD pattern was observed for Lu2O3:Eu films deposited by PLD at a substrate temperature higher than 400 °C [25] and by magnetron sputtering with thermal postdeposition treatment at 900 °C for 2 h [20]. The reflections in the XRD pattern can be assigned to a body-centered cubic (I 21 3) structure of Lu2O3, according to JCPDS Card NO: 96-101-0596 file. The Eu2O3 phase was not detected in the patterns, confirming the Eu dopant was substituting Lu in Lu2O3 host, which was supported by the closed values of the ionic radii of 0.95 Å and 0.85 Å for Eu3+ and Lu3+, respectively [25]. The broad hump around 2θ = 21° is characteristic for amorphous fused silica substrate.

4. Conclusions

The in situ monitoring system of optical properties (photoluminescence and transmission) at pulsed laser annealing processing of Eu-doped oxide thin films was demonstrated. Eu-doped ZnO, TiO2, and Lu2O3 films were fabricated by PLD at room temperature. The system allowed us to find quickly the optimal PLA conditions (ArF laser at λ = 193 nm, fluence, and number of PLA shots) for maximizing Eu3+ photoluminescence. The Eu3+ emission enhancement of 4.1×, 5× and 2.8×, after 800, 400, and 7 PLA shots, for ZnO, TiO2, and Lu2O3 matrix was obtained, respectively. Transmission was markedly modified at Lu2O3:Eu film, where also Eg increased to 5.51 eV. On the other hand, ZnO:Eu and TiO2:Eu films exhibited lowering Eg to 3.25 eV and 3.23 eV, respectively. TiO2:Eu and Lu2O3:Eu as-deposited films exhibited an amorphous character that was modified by PLA to anatase and cubic nanocrystalline phase, respectively. In the case of ZnO:Eu, the application of PLA induced rather surface smoothening-related grains’ coalescence.

Author Contributions

Writing—original draft preparation and project administration, M.N.; investigation, M.N., J.R., J.M.-C., L.V., S.A.I. and T.K.; visualization, J.R.; methodology, J.R. and S.A.I.; conceptualization, P.P.; formal analysis and data curation, Š.H., S.C. and M.V.; software and validation, P.F.; supervision, J.L. All authors have read and agreed to the published version of the manuscript.


This research and the APC was funded by Czech Science Foundation, grant number 18-17834S.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.


Many thanks to Ladislav Fekete for performing AFM measurements.

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.


  1. Daksh, D.; Agrawal, Y.K. Rare Earth-Doped Zinc Oxide Nanostructures: A Review. Rev. Nanosci. Nanotechnol. 2016, 5, 1–27. [Google Scholar] [CrossRef]
  2. Gupta, S.K.; Sudarshan, K.; Kadam, R. Optical nanomaterials with focus on rare earth doped oxide: A Review. Mater. Today Commun. 2021, 27, 102277. [Google Scholar] [CrossRef]
  3. Topping, S.G.; Sarin, V.K. CVD Lu2O3:Eu coatings for advanced scintillators. Int. J. Refract. Met. Hard Mater. 2009, 27, 498–501. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  4. Nagarkar, V.V.; Topping, S.G.; Miller, S.R.; Singh, B.; Brecher, C.; Sarin, V.K. Characterization of vapor-deposited Lu2O3: Eu3+ scintillator for x-ray imaging applications. In Penetrating Radiation Systems and Applications X; International Society for Optics and Photonics: Bellingham, WA, USA, 2009; Volume 7450, p. 745003. [Google Scholar] [CrossRef]
  5. Li, G.-R.; Dawa, C.-R.; Lu, X.-H.; Yu, X.-L.; Tong, Y.-X. Use of Additives in the Electrodeposition of Nanostructured Eu3+/ZnO Films for Photoluminescent Devices. Langmuir 2009, 25, 2378–2384. [Google Scholar] [CrossRef] [PubMed]
  6. Chen, P.; Wang, Z.; Wang, S.; Lyu, M.; Hao, M.; Ghasemi, M.; Xiao, M.; Yun, J.-H.; Bai, Y.; Wang, L. Luminescent europium-doped titania for efficiency and UV-stability enhancement of planar perovskite solar cells. Nano Energy 2020, 69, 104392. [Google Scholar] [CrossRef]
  7. Ezirmik, K.V. Concentration quenching of photoluminescence in optically transparent Lu2O3:Eu thin films deposited to be used as scintillators. Mater. Res. Express 2021, 8, 016407. [Google Scholar] [CrossRef]
  8. Zhu, C.; Lv, C.; Wang, C.; Sha, Y.; Li, D.; Ma, X.; Yang, D. Color-tunable electroluminescence from Eu-doped TiO(2)/p(+)-Si heterostructured devices: Engineering of energy transfer. Opt. Express 2015, 23, 2819–2826. [Google Scholar] [CrossRef] [PubMed]
  9. Murillo, A.G.; Romo, F.D.J.C.; Le Luyer, C.; Ramírez, A.D.J.M.; Hernández, M.G.; Palmerin, J.M. Sol–gel elaboration and structural investigations of Lu2O3:Eu3+ planar waveguides. J. Sol-Gel Sci. Technol. 2009, 50, 359–367. [Google Scholar] [CrossRef]
  10. Thoř, T.; Rubešová, K.; Jakeš, V.; Cajzl, J.; Nádherný, L.; Mikolášová, D.; Beitlerová, A.; Nikl, M. Europium-doped Lu2O3 phosphors prepared by a sol-gel method. IOP Conf. Series: Mater. Sci. Eng. 2019, 465, 012009. [Google Scholar] [CrossRef]
  11. Zhang, J.; Qin, Q.; Yu, M.; Zhou, M.; Wang, Y. The photoluminescence, afterglow and up conversion photostimulated luminescence of Eu3+ doped Mg2SnO4 phosphors. J. Lumin. 2012, 132, 23–26. [Google Scholar] [CrossRef]
  12. Binnemans, K. Interpretation of europium(III) spectra. Co-ord. Chem. Rev. 2015, 295, 1–45. [Google Scholar] [CrossRef] [Green Version]
  13. Miranda, S.; Peres, M.; Monteiro, T.; Alves, E.; Sun, H.; Geruschke, T.; Vianden, R.; Lorenz, K. Rapid thermal annealing of rare earth implanted ZnO epitaxial layers. Opt. Mater. 2011, 33, 1139–1142. [Google Scholar] [CrossRef]
  14. Najafi, M.; Haratizadeh, H. The effect of growth conditions and morphology on photoluminescence properties of Eu-doped ZnO nanostructures. Solid State Sci. 2015, 41, 48–51. [Google Scholar] [CrossRef]
  15. Kaszewski, J.; Kiełbik, P.; Wolska, E.; Witkowski, B.; Wachnicki, Ł; Gajewski, Z.; Godlewski, M.M. Tuning the luminescence of ZnO:Eu nanoparticles for applications in biology and medicine. Opt. Mater. 2018, 80, 77–86. [Google Scholar] [CrossRef]
  16. Wang, M.; Huang, C.; Huang, Z.; Guo, W.; Huang, J.; He, H.; Wang, H.; Cao, Y.; Liu, Q.; Liang, J. Synthesis and photoluminescence of Eu-doped ZnO microrods prepared by hydrothermal method. Opt. Mater. 2009, 31, 1502–1505. [Google Scholar] [CrossRef]
  17. Swapna, R.; Srinivasa Reddy, T.; Venkateswarlu, K.; Kumar, M.S. Effect of Post-Annealing on the Properties of Eu Doped ZnO Nano Thin Films. Procedia Mater. Sci. 2015, 10, 723–729. [Google Scholar] [CrossRef] [Green Version]
  18. Al-Shomar, S.M. Synthesis and characterization of Eu3+ doped TiO2 thin films deposited by spray pyrolysis technique for photocatalytic application. Mater. Res. Express 2021, 8, 026402. [Google Scholar] [CrossRef]
  19. Akazawa, H.; Shinojima, H. Switching photoluminescence channels between dopant Eu2+ and Eu3+ ions in ZnO thin films by varying the post-annealing conditions. J. Appl. Phys. 2016, 120, 123101. [Google Scholar] [CrossRef]
  20. Topping, S.G.; Park, C.H.; Rangan, S.K.; Sarin, V.K. Lutetium Oxide Coatings by PVD. MRS Online Proc. Library (OPL) 2007, 1038, 115–120. [Google Scholar] [CrossRef] [Green Version]
  21. Roy, S.; Topping, S.; Sarin, V. Growth and Characterization of Lu2O3:Eu3+ Thin Films on Single-Crystal Yttria-Doped Zirconia. JOM 2013, 65, 557–561. [Google Scholar] [CrossRef]
  22. Marton, Z.; Miller, S.R.; Brecher, C.; Kenesei, P.; Moore, M.D.; Woods, R.; Almer, J.D.; Miceli, A.; Nagarkar, V.V. Efficient high-resolution hard X-ray imaging with transparent Lu2O3:Eu scintillator thin films. In Medical Applications of Radiation Detectors V; International Society for Optics and Photonics: Bellingham, WA, USA, 2015; Volume 9594, p. 95940E. [Google Scholar] [CrossRef]
  23. Márton, Z.; Bhandari, H.B.; Brecher, C.; Miller, S.R.; Singh, B.; Nagarkar, V.V. High efficiency microcolumnar Lu2O3:Eu scintillator thin film for hard X-ray microtomography. J. Physics: Conf. Ser. 2013, 425, 062016. [Google Scholar] [CrossRef] [Green Version]
  24. Novotny, M.; Vondráček, M.; Marešová, E.; Fitl, P.; Bulíř, J.; Pokorný, P.; Havlová, Š.; Abdellaoui, N.; Pereira, A.; Hubík, P.; et al. Optical and structural properties of ZnO:Eu thin films grown by pulsed laser deposition. Appl. Surf. Sci. 2019, 476, 271–275. [Google Scholar] [CrossRef]
  25. Martinet, C.; Pillonnet, A.; Lancok, J.; Garapon, C. Optical, structural and fluorescence properties of nanocrystalline cubic or monoclinic Eu:Lu2O3 films prepared by pulsed laser deposition. J. Lumin. 2007, 126, 807–816. [Google Scholar] [CrossRef]
  26. Le Boulbar, E.; Millon, E.; Boulmer-Leborgne, C.; Cachoncinlle, C.; Hakim, B.; Ntsoenzok, E. Optical properties of rare earth-doped TiO2 anatase and rutile thin films grown by pulsed-laser deposition. Thin Solid Films 2014, 553, 13–16. [Google Scholar] [CrossRef]
  27. Irimiciuc, S.; More-Chevalier, J.; Chertpalov, S.; Fekete, L.; Novotný, M.; Havlová, Š.; Poupon, M.; Zikmund, T.; Kůsová, K.; Lančok, J. In-situ plasma monitoring by optical emission spectroscopy during pulsed laser deposition of doped Lu2O3. Appl. Phys. A 2021, 127, 1–9. [Google Scholar] [CrossRef]
  28. Camps, I.; Borlaf, M.; Colomer, M.T.; Moreno, R.; Duta, L.; Nita, C.; del Pino, A.P.; Logofatu, C.; Serna, R.; György, E. Structure-property relationships for Eu doped TiO2 thin films grown by a laser assisted technique from colloidal sols. RSC Adv. 2017, 7, 37643–37653. [Google Scholar] [CrossRef] [Green Version]
  29. Garcıa-Murillo, A.; Le Luyer, C.; Dujardin, C.; Martin, T.; Garapon, C.; Pédrini, C.; Mugnier, J. Elaboration and scintillation properties of Eu3+-doped Gd2O3 and Lu2O3 sol–gel films. Nucl. Instrum. Methods Phys. Res. Sect. A Accel. Spectromet. Detect. Assoc. Equip. 2002, 486, 181–185. [Google Scholar] [CrossRef]
  30. Fhoula, M.; Kallel, T.; Messaoud, M.; Dammak, M.; Cavalli, E. Morphological, spectroscopic and photocatalytic properties of Eu3+:TiO2 synthesized by solid-state and hydrothermal-assisted sol-gel processes. Ceram. Int. 2019, 45, 3675–3679. [Google Scholar] [CrossRef]
  31. Frindell, K.L.; Bartl, M.H.; Popitsch, A.; Stucky, G.D. Sensitized Luminescence of Trivalent Europium by Three-Dimensionally Arranged Anatase Nanocrystals in Mesostructured Titania Thin Films. Angew. Chem. Int. Ed. 2002, 41, 959–962. [Google Scholar] [CrossRef]
  32. Ramírez, A.D.J.M.; Hernández, M.G.; Murillo, A.G.; Romo, F.D.J.C.; Palmerin, J.M.; Velazquez, D.Y.M.; Jota, M.L.C. Structural and Luminescence Properties of Lu2O3:Eu3+ F127 Tri-Block Copolymer Modified Thin Films Prepared by Sol-Gel Method. Materials 2013, 6, 713–725. [Google Scholar] [CrossRef] [Green Version]
  33. Chen, P.; X. Ma, X.; Yang, D. ZnO:Eu thin-films: Sol–gel derivation and strong photoluminescence from 5D0→7F0 transition of Eu3+ ions. J. Alloy. Compd. 2007, 431, 317–320. [Google Scholar] [CrossRef]
  34. Can, N.; Townsend, P.D.; Hole, D.E.; Snelling, H.; Ballesteros, J.M.; Afonso, C.N. Enhancement of luminescence by pulse laser annealing of ion-implanted europium in sapphire and silica. J. Appl. Phys. 1995, 78, 6737–6744. [Google Scholar] [CrossRef] [Green Version]
  35. Can, N.; Townsend, P.D.; Hole, D.E.; Afonso, C.N. High intensity luminescence from pulsed laser annealed europium implanted sapphire. Appl. Phys. Lett. 1994, 65, 1871–1873. [Google Scholar] [CrossRef] [Green Version]
  36. Ozerov, I.; Arab, M.; Safarov, V.; Marine, W.; Giorgio, S.; Sentis, M.; Nanai, L. Enhancement of exciton emission from ZnO nanocrystalline films by pulsed laser annealing. Appl. Surf. Sci. 2004, 226, 242–248. [Google Scholar] [CrossRef] [Green Version]
  37. Havlová, Š.; Novotný, M.; Fitl, P.; More-Chevalier, J.; Remsa, J.; Kiisk, V.; Kodu, M.; Jaaniso, R.; Hruška, P.; Lukáč, F.; et al. Effect of pulsed laser annealing on optical and structural properties of ZnO:Eu thin film. J. Mater. Sci. 2021, 56, 11414–11425. [Google Scholar] [CrossRef]
  38. Chen, Z.; Jiang, S.; Xin, B.; Guo, R.; Miao, D. Microstructures and luminescent properties of CO2 laser annealed Y2O3:Eu3+ thin films grown on quartz fabric by electron beam evaporation. Text. Res. J. 2018, 88, 1824–1833. [Google Scholar] [CrossRef]
  39. Jota, M.C.; Murillo, A.G.; Romo, F.C.; Hernández, M.G.; Ramírez, A.D.J.M.; Velumani, S.; Cruz, E.D.L.R.; Kassiba, A. Lu2O3:Eu3+ glass ceramic films: Synthesis, structural and spectroscopic studies. Mater. Res. Bull. 2014, 51, 418–425. [Google Scholar] [CrossRef]
  40. Xu, M.; Zhang, W.; Dong, N.; Jiang, Y.; Tao, Y.; Yin, M. Preparation and characterization of optical spectroscopy of Lu2O3:Eu nanocrystals. J. Solid State Chem. 2005, 178, 477–482. [Google Scholar] [CrossRef]
  41. Jurek, K.; Szczesny, R.; Trzcinski, M.; Ciesielski, A.; Borysiuk, J.; Skowronski, L. The Influence of Annealing on the Optical Properties and Microstructure Recrystallization of the TiO2 Layers Produced by Means of the E-BEAM Technique. Materials 2021, 14, 5863. [Google Scholar] [CrossRef] [PubMed]
  42. Özgür, Ü.; Alivov, Y.I.; Liu, C.; Teke, A.; Reshchikov, M.A.; Doğan, S.; Avrutin, V.; Cho, S.J.; Morkoç, H. A comprehensive review of ZnO materials and devices. J. Appl. Phys. 2005, 98, 041301. [Google Scholar] [CrossRef] [Green Version]
  43. Zhang, D.; Lin, W.; Lin, Z.; Jia, L.; Zheng, W.; Huang, F. Lu2O3: A promising ultrawide bandgap semiconductor for deep UV photodetector. Appl. Phys. Lett. 2021, 118, 211906. [Google Scholar] [CrossRef]
  44. Peres, M.; Cruz, A.; Pereira, S.; Correia, M.R.; Soares, M.; Neves, A.; Carmo, M.; Monteiro, T.; Martins, M.; Trindade, T.; et al. Optical studies of ZnO nanocrystals doped with Eu3+ ions. Appl. Phys. A 2007, 88, 129–133. [Google Scholar] [CrossRef]
  45. Zhang, Y.; Liu, Y.; Wu, L.; Xie, E.; Chen, J. Photoluminescence and ZnO→Eu3+energy transfer in Eu3+-doped ZnO nanospheres. J. Phys. D Appl. Phys. 2009, 42, 085106. [Google Scholar] [CrossRef]
  46. Ningthoujam, R.; Gajbhiye, N.S.; Ahmed, A.; Umre, S.S.; Sharma, S.J. Re-Dispersible Li+ and Eu3+ Co-Doped Nanocrystalline ZnO: Luminescence and EPR Studies. J. Nanosci. Nanotechnol. 2008, 8, 3059–3062. [Google Scholar] [CrossRef]
  47. Ishizumi, A.; Kanemitsu, Y. Structural and luminescence properties of Eu-doped ZnO nanorods fabricated by a microemulsion method. Appl. Phys. Lett. 2005, 86, 253106. [Google Scholar] [CrossRef] [Green Version]
  48. Nedyalkov, N.; Koleva, M.; Nikov, R.; Atanasov, P.; Nakajima, Y.; Takami, A.; Shibata, A.; Terakawa, M. Laser nanostructuring of ZnO thin films. Appl. Surf. Sci. 2016, 374, 172–176. [Google Scholar] [CrossRef]
  49. Chen, X.; Luo, W. Optical Spectroscopy of Rare Earth Ion-Doped TiO2 Nanophosphors. J. Nanosci. Nanotechnol. 2010, 10, 1482–1494. [Google Scholar] [CrossRef] [PubMed]
  50. Yin, J.; Xiang, L.; Zhao, X. Monodisperse spherical mesoporous Eu-doped TiO2 phosphor particles and the luminescence properties. Appl. Phys. Lett. 2007, 90, 113112. [Google Scholar] [CrossRef]
  51. Makuła, P.; Pacia, M.; Macyk, W. How To Correctly Determine the Band Gap Energy of Modified Semiconductor Photocatalysts Based on UV–Vis Spectra. J. Phys. Chem. Lett. 2018, 9, 6814–6817. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  52. Skowronski, L.; Zdunek, K.; Nowakowska-Langier, K.; Chodun, R.; Trzcinski, M.; Kobierski, M.; Kustra, M.; Wachowiak, A.; Wachowiak, W.; Hiller, T.; et al. Characterization of microstructural, mechanical and optical properties of TiO2 layers deposited by GIMS and PMS methods. Surf. Coat. Technol. 2015, 282, 16–23. [Google Scholar] [CrossRef]
  53. Wei, H.; Ma, X.; Gu, L.; Li, J.; Si, W.; Ou, G.; Yu, W.; Zhao, C.; Li, J.; Song, M.; et al. Aerodynamic levitated laser annealing method to defective titanium dioxide with enhanced photocatalytic performance. Nano Res. 2016, 9, 3839–3847. [Google Scholar] [CrossRef]
  54. Pan, H.; Ko, S.H.; Misra, N.; Grigoropoulos, C.P. Laser annealed composite titanium dioxide electrodes for dye-sensitized solar cells on glass and plastics. Appl. Phys. Lett. 2009, 94, 071117. [Google Scholar] [CrossRef] [Green Version]
  55. Serga, V.; Burve, R.; Krumina, A.; Pankratova, V.; Popov, A.I.; Pankratov, V. Study of phase composition, photocatalytic activity, and photoluminescence of TiO2 with Eu additive produced by the extraction-pyrolytic method. J. Mater. Res. Technol. 2021, 13, 2350–2360. [Google Scholar] [CrossRef]
  56. Jia, G.; Zheng, Y.; Liu, K.; Song, Y.; You, H.; Zhang, H. Facile Surfactant- and Template-Free Synthesis and Luminescent Properties of One-Dimensional Lu2O3:Eu3+ Phosphors. J. Phys. Chem. C 2009, 113, 153–158. [Google Scholar] [CrossRef]
  57. Zych, E.; Trojan-Piegza, J.; Kępiński, L. Homogeneously precipitated Lu2O3:Eu nanocrystalline phosphor for X-ray detection. Sens. Actuat. B Chem. 2005, 109, 112–118. [Google Scholar] [CrossRef]
  58. Pedroso, C.C.S.; de Carvalho, J.M.; Rodrigues, L.C.V.; Hölsä, J.; Brito, H. Rapid and Energy-Saving Microwave-Assisted Solid-State Synthesis of Pr3+-, Eu3+-, or Tb3+-Doped Lu2O3 Persistent Luminescence Materials. ACS Appl. Mater. Interfaces 2016, 8, 19593–19604. [Google Scholar] [CrossRef] [PubMed]
  59. Wiktorczyk, T. Optical properties of electron beam deposited lutetium oxide thin films. Opt. Applicata 2001, 31, 83–92. [Google Scholar]
  60. Strek, W.; Zych, E.; Hreniak, D. Size effects on optical properties of Lu2O3:Eu3+ nanocrystallites. J. Alloy. Compd. 2002, 344, 332–336. [Google Scholar] [CrossRef]
Figure 1. PLA and in situ optical properties’ measurement experimental setup.
Figure 1. PLA and in situ optical properties’ measurement experimental setup.
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Figure 2. PL emission spectra of ZnO:Eu thin film, dependence on the number of PLA shots.
Figure 2. PL emission spectra of ZnO:Eu thin film, dependence on the number of PLA shots.
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Figure 3. Transmittance spectra ZnO:Eu thin film, dependence on the number of PLA shots.
Figure 3. Transmittance spectra ZnO:Eu thin film, dependence on the number of PLA shots.
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Figure 4. AFM surface images of ZnO:Eu thin film (a) as deposited and (b) after PLA processing, 800 shots.
Figure 4. AFM surface images of ZnO:Eu thin film (a) as deposited and (b) after PLA processing, 800 shots.
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Figure 5. XRD patterns of ZnO:Eu thin film (as deposited and after PLA processing, 800 shots), (a) 2theta-omega and (b) grazing incidence scans.
Figure 5. XRD patterns of ZnO:Eu thin film (as deposited and after PLA processing, 800 shots), (a) 2theta-omega and (b) grazing incidence scans.
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Figure 6. PL emission spectra of TiO2:Eu thin film, dependence on the number of PLA shots.
Figure 6. PL emission spectra of TiO2:Eu thin film, dependence on the number of PLA shots.
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Figure 7. Transmittance spectra TiO2:Eu thin film, dependence on the number of PLA shots.
Figure 7. Transmittance spectra TiO2:Eu thin film, dependence on the number of PLA shots.
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Figure 8. AFM surface images of TiO:Eu thin film (a) as deposited and (b) after PLA processing, 400 shots.
Figure 8. AFM surface images of TiO:Eu thin film (a) as deposited and (b) after PLA processing, 400 shots.
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Figure 9. XRD patterns of TiO2:Eu thin film (as deposited and after PLA processing, 400 shots), (a) 2theta-omega and (b) grazing incidence scans.
Figure 9. XRD patterns of TiO2:Eu thin film (as deposited and after PLA processing, 400 shots), (a) 2theta-omega and (b) grazing incidence scans.
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Figure 10. Emission spectra of Lu2O3:Eu thin film, dependence on the number of PLA shots.
Figure 10. Emission spectra of Lu2O3:Eu thin film, dependence on the number of PLA shots.
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Figure 11. Transmittance spectra Lu2O3:Eu thin film, dependence on the number of PLA shots.
Figure 11. Transmittance spectra Lu2O3:Eu thin film, dependence on the number of PLA shots.
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Figure 12. AFM surface images of Lu2O3:Eu thin film (a) as deposited and (b) after PLA processing, seven shots.
Figure 12. AFM surface images of Lu2O3:Eu thin film (a) as deposited and (b) after PLA processing, seven shots.
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Figure 13. XRD patterns of Lu2O3:Eu thin film (as deposited and after PLA processing, seven shots), (a) 2theta-omega and (b) grazing incidence scans.
Figure 13. XRD patterns of Lu2O3:Eu thin film (as deposited and after PLA processing, seven shots), (a) 2theta-omega and (b) grazing incidence scans.
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Table 1. The deposition and laser annealing conditions.
Table 1. The deposition and laser annealing conditions.
MaterialFluence PLD
O2 Pressure
Deposition Time
Fluence PLA
ZnO:Eu (1% at. Eu)5158.3840–1000175
(1% at. Eu)
Lu2O3:Eu (3% at. Eu)52.520110-150150
Table 2. Properties, modifications after PLA.
Table 2. Properties, modifications after PLA.
MaterialEu3+ (5D07F2)
PL Emission
Band Gap Eg
S a
S q
PLAAs DepositedPLAAs DepositedPLA
ZnO:Eu 4.1×3.283.2514.6
Lu2O3:Eu 2.8×5.475.512.0
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Novotný, M.; Remsa, J.; Havlová, Š.; More-Chevalier, J.; Irimiciuc, S.A.; Chertopalov, S.; Písařík, P.; Volfová, L.; Fitl, P.; Kmječ, T.; et al. In Situ Monitoring of Pulsed Laser Annealing of Eu-Doped Oxide Thin Films. Materials 2021, 14, 7576.

AMA Style

Novotný M, Remsa J, Havlová Š, More-Chevalier J, Irimiciuc SA, Chertopalov S, Písařík P, Volfová L, Fitl P, Kmječ T, et al. In Situ Monitoring of Pulsed Laser Annealing of Eu-Doped Oxide Thin Films. Materials. 2021; 14(24):7576.

Chicago/Turabian Style

Novotný, Michal, Jan Remsa, Šárka Havlová, Joris More-Chevalier, Stefan Andrei Irimiciuc, Sergii Chertopalov, Petr Písařík, Lenka Volfová, Přemysl Fitl, Tomáš Kmječ, and et al. 2021. "In Situ Monitoring of Pulsed Laser Annealing of Eu-Doped Oxide Thin Films" Materials 14, no. 24: 7576.

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