Luminescence studies on SnO₂ and SnO₂:Eu nanocrystals grown by laser assisted flow deposition

Abstract

Transparent conductive tin oxide materials have been a research topic extensively studied in recent years due to the great interest for many applications. However, in most of them, the pure form is rarely used, being usually modified by the incorporation of dopants. Selecting the most appropriate technique to develop nanocrystals of doped tin oxide and understanding the influence of dopant on the optical properties are the challenges that need to be addressed when envisaging devices. To fulfill this objective, the recently developed laser assisted flow deposition (LAFD) method is explored to grow SnO2 and SnO2:Eu nanocrystals. The morphology of these nanocrystals was investigated by scanning electron microscopy and well defined prismatic nanocrystals with sizes of ∼60 nm were identified. The crystalline quality assessed by X-ray diffraction measurements and Raman spectroscopy indicates that the produced nanocrystals are monophasic and crystallize in the tetragonal rutile structure. Steady state luminescence studies provide the information on the optical active centres in the SnO2 and SnO2:Eu nanocrystals. For the undoped samples only broad emission bands were observed by pumping the samples in the ultraviolet region. The broad emission was found to be an overlap of green and red optical centres as identified by temperature and excitation intensity dependent luminescence. The latter was found to exhibit an excitonic-related behaviour and the green emission was found to be of utmost importance to discuss the intraionic luminescence in the doped samples. For the SnO2:Eu nanocrystals the luminescence is dominated by the magnetic allowed (5)D0 → (7)F1 transition with the ions in almost undistorted centrosymmetric sites. The ion luminescence integrated intensity is found to increase with increasing temperatures being well accounted for a thermal population provided by the thermal quenching of the green band.

A review on the laser-assisted flow deposition method: growth of ZnO micro and nanostructures

“…In this paper, we report such a vapour-based method, designated by laser-assisted flow deposition (LAFD), which has been developed by our research group in the last few years. This technique exhibits a high yield of micro and nanostructures' production, with potential for scalable applications [18][19][20][21][22] . Some key advantages regarding the traditional methods include being catalyst-free, remotely heating by the use of a focused laser beam and the reduced presence of undesired contaminations, since neither crucibles nor additional reagents/solvents besides the materials' precursors are needed.…”

“…Therefore, only materials that fill these requirements can be grown by LAFD. Up to now, our group have successfully grown both ZnO 5,18,19,21,22,26 and tin oxide (SnO2) 20 micro and nanostructures. Moreover, by incorporating additional compounds into the precursors, it is possible to achieve the formation of intentionally doped materials 20 , as well as composites structures 21 in a single growth step, avoiding additional and time-consuming procedures.…”

Structural Evolution and Photoluminescence of SiO2 Layers with Sn Nanoclusters Formed by Ion Implantation

“…Simultaneously, one can see an increase in the intensity in the spectral range of 1.8-2.9 eV. Most probably, the weak and broad band in this spectral range originates from defects in both SnO 2 (Sn and O interstitials, dangling bonds, or oxygen vacancies) [5,9,24,25,27,31] and SiO 2 matrix [24,30,32,33] and also from the formation of the SnO x phase [34]. It is noncontradictory, and the contribution of defects in the SiO 2 matrix and SnO x phase in emission would be higher from the more deep layers due to lower concentration of Sn atoms and oxygen atoms diffused from air.…”

Highlights on advances in SnO2 quantum dots: insights into synthesis strategies, modifications and applications

“…Pulsed laser ablation of starting material, as a 'top-down' strategy, is a versatile method to produce nanoparticles. Using Sn or SnO as starting materials, some research groups have fabricated SnO 2 QDs by pulsed laser ablation of Sn or SnO [40,[58][59][60][61][62]. Singh et al [58] have synthesized SnO 2 QDs with the average diameter of 2.5 nm by laser ablation of metal Sn in water.…”