Growth and Properties of Cd-doped PbI2 Crystals

Authors O.V. Rybak, I.V. Semkiv , M.V. Chekailo

Lviv Polytechnic National University, 12, St. Bandery St., Lviv 79013, Ukraine

Issue Volume 12, Year 2020, Number 1
Dates Received 29 December 2019; revised manuscript received 17 February 2020; published online 25 February 2020
Citation O.V. Rybak, I.V. Semkiv, M.V. Chekailo, J. Nano- Electron. Phys. 12 No 1, 01019 (2020)
PACS Number(s) 81.10.Bk, 61.72.uf,, 61.05.cj, 78.40.Fy
Keywords Lead iodide, Mass-transfer rate, Doping (20) , Cadmium dopant, Diffraction patterns, Absorption spectra.

PbI2 single crystals containing cadmium 0.001-10 at. % have been obtained by means of crystallization from vapor phase in an enclosed system with over-stoichiometric iodine vapor pressure. The influence of cadmium concentration in source burden material and the influence of temperature gradient upon the mass-transfer rate in the system and on the crystals’ characteristics have been researched. With addition of cadmium within the concentration range from 0.001 to 0.5 at. % into PbI2-I2 system at optimal growing conditions for pure PbI2 crystals, the mass-transfer rate is decreased by not more than 2 %, while Cd concentration in the single crystals grown remains of the same order as their content in the source material. The increase of dopant content from 0.5 to 5.5 at. % in the source material leads to two-fold decrease of mass-transfer rate compared to its initial value, with cadmium content in single crystals 5 times lower than in the source material and with decreased dimensions of single crystals. To obtain Cd-doped crystals up to 10 at. %, temperature gradient in the system has been decreased. Cd doping facilitates the growth of single crystals mainly in the form of plates and tapes. By means of X-ray diffraction spectra, it has been defined that PbI2 single crystals belong to 4H-polytype. The lattice parameters and the unit cell volume of pure and doped crystals have been determined. The influence of cadmium dopant upon the PbI2 absorption spectra has been defined. Increasing cadmium content in PbI2 crystals to 3 at. % results in a shift of intrinsic absorption edge into the short-wave area and increase of the band gap width.

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