Optical spectroscopy and unusual temperature shift of f – f zero-phonon luminescence lines: KTaO₃:Er

Abstract

We present a study of KTaO₃:Er (≈0.05%) single crystals based on a multifaceted approach including the use of optical absorption, far-infrared reflectivity, electron paramagnetic resonance, photoluminescence spectra, and ab initio simulations. We describe briefly the fundamental consequences of Er doping, in particular, stiffening of TO1 soft mode of KTaO₃. We provide information about energy level structures controlling f – f optical transitions in Er³⁺, on formation of minor cubic octahedral and major orthorhombic Er³⁺ centers. It is revealed that the temperature shift of narrow zero-phonon emission lines is strikingly unusual being much larger than that typical for trivalent rare-earth impurities.

Keywords:

• ABO₃ incipient ferroelectrics
• rare-earth impurities
• zero-phonon emission lines

Acknowledgments

V.A.T. kindly thanks R. V. Yusupov and B. S. Malkin for valuable discussions. The computations were carried out using facilities of the Resource Center “Computer Center of SPbU”, St. Petersburg, Russia. The equipment of Ural Center for Shared Use “Modern Nanotechnology” Ural Federal University (Reg. № 2968) was used.

Additional information

Funding

This work was supported in part by the Project “Center of Advanced Applied Sciences”, No. CZ.02.1.01/0.0/0.0/16-019/0000778, of the Operational Program Research, Development and Education, and MEYS Project No. SOLID21, CZ.02.1.01/0.0/0.0/16_019/0000760.