Growth of Highly Anisotropic 2D Ternary CaTe2O5 Flakes on Molten Glass

Two-dimensional (2D) ternary compounds (2DTCs) have attracted intensive attention due to the new degree of freedom of modulating physical and chemical properties. However, the controllable synthesis of 2DTCs still remains a great challenge impeding further research and applications. Here, for the first time, ultrathin (approximate to 7.4 nm) epsilon-CaTe2O5 flakes with high anisotropy are obtained by a chemical vapor deposition method using soda-lime glass as the capture substrate. The molten glass adsorbs Te vapor in the gas flow to its surface, which reacts with CaO in the molten substrate leading to the precipitation of epsilon-CaTe2O5. Interestingly, epsilon-CaTe2O5 flakes display highly anisotropic band structures and optical properties. Furthermore, low-temperature electrical measurements show that the metal-semiconductor/insulator transition of epsilon-CaTe2O5 is exhibited at about 130 K, and optical phonon assisted hopping of small polarons becomes dominant within the temperature range of 130-300 K. Employing soda-lime glass as the capture substrate may provide a new approach for the synthesis of 2DTCs.