Crystal Growth And Physical Properties Of Novel Low-Dimensional Materials CsV₆Bi₅ And TaCoTe₂

In the research field of material physics,the decrease of the dimension makes lowdimensional systems very sensitive to carrier concentration,pressure,electric field,magnetic field,and so on,thus the low-dimensional materials always exhibit many novel properties.In addition,the applications of low-dimensional materials have made great progress,which has attracted enormous interest in the industry.However,these single crystals only represent a small fraction of low-dimensional materials that have been discovered,which limits the further exploration of new low-dimensional structures and novel properties to some extent.It still exists great potential to explore.The growth and synthesis of new materials are one of the driving forces to promote the development of low-dimensional materials.At the same time,tremendous effort has been devoted to explore new properties and novel applications of low-dimensional systems by thickness-tuned,doping,gate-tuned,heterostructure and so on and brings new opportunities and challenges.The innovation and research significance of this paper are as following.We have prepared two new low-dimensional materials,and made relatively study on the crystal growth of these materials and basic properties.The main contents of this paper can be introduced through the following two aspects:1.We synthesized quasi-one-dimensional CsV₆Bi₅ single crystals via flux method for the first time in the world.The structure information about space group of CsV₆Bi₅ was verified by taking high resolution image of CsV₆Bi₅.We also have operated a series of measurements on the electrical,magnetic and optical properties of CsV₆Bi₅ single crystals.We found that CsV₆Bi₅ single undergoes a phase transition around 120 K,and some of them exhibit superconducting（T_c～3.5 K）at low temperature with the decrease of temperature.The quasi-one-dimensional structure of CsV₆Bi₅ and its fibrous structure indicate that the system has great potential in exploring new superconductors.2.The high quality TaCoTe2 single crystals were grown by chemical vapor transport（CVT）method using TeCl4 as transport agent and we discovered TaCoTe2 was a two-dimensional material which can be easily exfoliated.Measurements on the crystal structure,electrical and magnetic properties of TaCoTe2 single crystals were carried out.The temperature dependence curve of the resistivity of TaCoTe2 single crystals showed a transition from semiconductor to metallic behavior around T=38 K during the cooling process.Another noteworthy point was that an upward resistivity warping appeared at lower temperatures when we applied magnetic field on the sample.In addition,based on the low exfoliation energy of TaCoTe2,thickness-dependent TaCoTe2 micro/nano devices were prepared.We research on the electrical properties of micro/nano devices and found that the electrical properties of bulk crystal and the nanoflakes even down to 18 nm are almost the same.The results showed that TaCoTe2 has great potential for being explored further properties such as Dirac antiferromagnetic behavior when the material was exfoliated to mono layer.