Vapor-phase Synthesis And Photoelectric Properties Of Two-Dimensional Ternary CaTe₂O₅

In ultra-thin structures of two-dimensional?2D?materials,charge carriers,heat and photon transport are confined in a 2D plane,which can cause singular electrical,optical,mechanical and catalytic properties compared to other bulk materials.Due to the addition of the third element,2D ternary compounds?2DTCs?are given a new degree of freedom in the regulation of properties and lattice structure,which will bring new application prospects in electronics,optoelectronic,biological sensors and catalysis.?-CaTe₂O₅ is a semiconductor material with an indirect band gap of 3.3 eV and has a low symmetry monoclinic structure.Its optical and electrical anisotropy is a promising research direction,but the synthesis of two-dimensional?-CaTe₂O₅ still remains challenging.Therefore,this thesis mainly focuses on the controllable synthesis and anisotropy of two-dimensional?-CaTe₂O₅ flakes,the main research contents are as follows:?1?For the first time,we successfully synthesized the high crystalline and ultra-thin?⁷.4nm?two-dimensional?-CaTe₂O₅ flakes,using soda lime glass as the capture substrates by chemical vapor deposition?CVD?method.Controllable synthesis of high quality?-CaTe₂O₅was achieved by adjusting parameters such as temperature.?2?The theoretical calculation results show that the band structure of?-CaTe₂O₅ has strong anisotropy,and the strain-dependence of the band gap along the a,b and c axes is different.Raman spectroscopy shows that the?-CaTe₂O₅ nanoflakes have strong in-plane anisotropy.The Raman peak at 124 cm^-1 decreases linearly with temperature and has a large first-order linear temperature coefficient.?3?The low temperature electrical transport test shows that?-CaTe₂O₅ will undergo metal-semiconductor/insulator transition around 130 K.and optical phonon assisted hopping of small polarons becomes dominant within the temperature range of 130-300 K.