Investigation of Optical and Pyroelectric Properties of Lithium Niobate Single Crystals Caused by Metal Ions Diffusion

Authors U.V. Yakhnevych1, G. Suchaneck2 , A. Eydam2, D.Yu. Sugak1,3, I.І. Syvorotka1,3, V.G. Haiduchok1,3, O.A. Buryy1, S.B. Ubizskii1, G. Gerlach2

1Department of Semiconductor Electronics, Lviv Polytechnic National University, 12, Bandera Str., 79000 Lviv, Ukraine

2Solid State Electronics Laboratory, TU Dresden, 01062 Dresden, Germany

3Scientific Research Company “Electron-Carat”, 202, Stryiska Str., Lviv, Ukraine

Issue Volume 11, Year 2019, Number 1
Dates Received 11 December 2018; revised manuscript received 07 February 2019; published online 25 February 2019
Citation U.V. Yakhnevych, G. Suchaneck, A. Eydam, et al., J. Nano- Electron. Phys. 11 No 1, 01017 (2019)
PACS Number(s) 66.30. – h, 78.20. – e, 77.70. + a
Keywords LiNbO3 single crystals, Dopant diffusion depth profile, Pyroelectric coefficient depth profile.

Spatial changes of optical and pyroelectric properties of doped LiNbO3 single crystals were investigated. Doping with Cu and Fe was performed after crystal growth by thermal diffusion at elevated temperatures. The crystals were all-side-covered by corresponding metal oxide powder before annealing. In order to reveal the role of various types of diffusion sources in the formation of the modified layers of LiNbO3, the same investigations were performed on the samples covered by copper films before annealing. The optical absorption spectra of the samples were recorded in a direction perpendicular to the direction of diffusion at different distances from the crystal surface. The intensities of the absorption bands of Cu+ (400 nm), Cu2+ (1000 nm) and Fe3+ (480 nm) ions were analyzed depending on the annealing temperature and the distance from the source of diffusion. The maxima were obtained on the depth profiles of additional absorption for all samples. The concentrations of Cu and Fe ions were calculated in accordance with the Smakula-Dexter formula. For the determination of correlation of the changes of optical and pyroelectric properties, the profiles of pyroelectric coefficient in the doped crystals were investigated by the laser intensity modulation method. To avoid the measurement uncertainty of thermal wave method that increases with increasing depth, the pyroelectric current was registered under excitation from both the front and the back sides of the sample. The averaged pyroelectric coefficients were also determined for calibration of the results. Here, a Peltier stage provided a sinusoidal modulation of the sample temperature at a frequency of 0.1 Hz. It is shown that diffusion doping affects the pyroelectric properties of lithium niobate crystals.

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