Large Area Synthesis And Phase-Control Of MoTe₂ Film

Since graphene was synthesized by accident in 2004,two dimensional materials have been attracting increasing interest because of their unique structure and prominent properties,which make them promising materials for a wide range of applications related to,e.g.,electronics,optoelectronics,energy storage,composite material,catalysis and sensor.Except for graphene,transition metal dichalcogenides?TMDCs?is one of the most remarkable two-dimensional materials in recent years.Although the study of bulk TMDCs has decades of history,monolayer or few-layered 2D TMDCs gains the popularities of researchers with the development of synthesis method and characterization tools for two dimensional material.Among TMDCs family,the study of MoTe₂ is still in start stage,the research of its properties and application is based on the controlled synthesis of high quality MoTe₂,which is important and difficult at the same time.In this paper,we synthesize MoTe₂ films by chemical vapor deposition,and we realize the phase control of MoTe₂ by adjusting the experiment conditions in the growth process.Two phases of large area MoTe₂ films can be synthesized on one silicon wafer,and single phase?1T'or 2H?MoTe₂ can also be grown on the whole area of silicon wafer.The main contents are as follows:1.We use single temperature zone tube furnace to synthesize large area MoTe₂ films on silicon wafer.2.1T'phase MoTe₂ films are always produced right above the Te powder,however,the phase of MoTe₂ located on the edge of silicon wafer depends on the cooling rate when the experiment is finished.That is,large area 2H phase MoTe₂ films can be synthesized in slow cooling rate,while 1T'-2H phase MoTe₂ homojunctions can be synthesized in fast cooling rate.A series of characterizations suggest that the synthesized MoTe₂ films is homogeneous and high-crystallinity,and there is no obvious transition region between two phases.3.The amount of tellurium and the distance between substrate and tellurium source make a difference in the concentration of Te vapor,as well as the phase of the MoTe₂ film.What's more,MoTe₂ films of large area and single phase can be grown successfully on the substrate that is facing down and located about 3cm away upstream or downstream from Te powder.