Topic: Advances in solid state materials synthesis, new solids and compounds
Bc. Karla Jeníčková
University of Chemistry and Technology, Prague, Czech republic
Department of Inorganic Chemistry
K. Jeníčková1*, J. Cajzl1, P. Nekvindová1, A. Macková2,3
1 Department of Inorganic Chemistry, University of Chemistry and Technology, Technická 5, 166 28 Prague, Czech Republic;
2 Nuclear Physics Institute, Czech Academy of Sciences, v. v. i., 250 68 Řež, Czech Republic; 3 Department of Physics, J.E. Purkinje University, České mládeže 8, 400 96 Ústí nad Labem,
Czech Republic;
* E-mail: jenickok@vscht.cz
Keywords: annealing, atmospheres, ZnO, defects, luminescence
In the last decade, ZnO has been intensively studied as a II-VI type semiconductor thanks to its excellent electro-optic, acousto-optic and piezoelectric properties, high electric conductivity and physical as well as chemical stability. ZnO is a crystal material with wurtzite structure, its most prominent properties include wide band gap and large binding energy. Properties which are interesting for photonics include wide transparency region and high refractive index. Moreover, ZnO exhibits intrinsic photoluminescence in the UV-VIS region, which is related to ZnO crystal structure defects such as oxygen vacancies or zinc and oxygen interstitials. Recently a tailoring of the band gap of ZnO has also become an important topic since ZnO material can be utilized in new-generation nanoscale photonics devices. Multiple studies have established a relationship between oxygen defects in ZnO structure and intrinsic photoluminescence and it has also been shown that the concentration of defects may be modified by using different annealing atmospheres. However, a systematic study focusing on the creation and migration of defects in various crystallographic cuts during annealing has been so far missing in literature. In this work, we present a systematic study of the behavior of defects in different crystallographic cuts of ZnO under different annealing atmospheres and its influence on intrinsic photoluminescence.
In our experiment, various ZnO crystallographic orientations were used, i.e. Z (0001), X (11‑20) and Y (10‑10). The dimensions of the samples were 1.0×1.0×0.3 mm. Thoroughly pre-cleaned wafers were annealed in vacuum or in oxygen and argon atmospheres for 1 hour at the temperature of 600 °C. The structural modifications of the ZnO single crystal structure after the annealing process were determined by Raman spectroscopy, X-Ray Diffraction (XRD) and Rutherford Backscattering Spectroscopy (RBS) and RBS/Channeling measurements. Photoluminescence measurements were performed at a room temperature in the range of 250–1000 nm for visible and near-infrared regions (VIS-NIR). The relationship between annealing conditions, structural changes and photoluminescence was evaluated. Obtained results confirmed the possibility of modifying the photoluminescence of ZnO connected to oxygen defects by using different crystallographic cuts and annealing atmospheres.
Acknowledgements
The research has been carried out at the CANAM (Centre of Accelerators and Nuclear Analytical Methods) infrastructure LM 2015056. This work was supported by the Czech Science Foundation (GACR No. 18-03346S).