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MOCVD of C-oriented Bi2Te3 Films on SiO2 Substrates using Triethyl Bismuth and Di-tertiarybutyl Tellurium

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Abstract

Metal-organic (MO)CVD of bismuth telluride thin films is investigated by using a combination of optimized bismuth and tellurium precursors along with H2 as a reactant gas. Good quality films are obtained, even at 300 °C. The Bi precursors are trimethyl bismuth (Bi(CH3)3, Bi(Me3)) and triethyl bismuth (Bi(C2H5)3, Bi(Et)3), and the Te precursors are diethyl tellurium (Te(C2H5)2, Te(Et)2), di-isopropyl tellurium (Te(C3H7)2, Te(iPr)2), and di-tertiarybutyl tellurium (Te(C4H9)2, Te(tBu)2). The integrated absorbance area of C-H stretching vibrations in the range 2800–3200 cm−1 is estimated to determine the decomposition rate of the Bi and Te precursors. C-oriented Bi2Te3 films are obtained at 300 °C and under 2.5 Torr using Bi(Et)3 and Te(tBu)2 and characterized. Further, the microstructure, crystallinity, and surface morphology of the films are determined. The appropriate stoichiometry of the bismuth telluride films is obtained as Bi/Te = 2:3. The combination of Bi(Et)3 and Te(tBu)2 is the most effective for low-temperature deposition because, compared to the other precursors, the decomposition of these precursors starts at a lower temperature. Investigations of the precursor decomposition behavior show that the absorbance of C-H stretching vibrations of ligands in precursors in the gas phase is sensitive to the analysis conditions.

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