Study On Scalable Phase-controlled CVD Growth,Transfer,and Electronic Properties Of MoTe₂ Nanoribbon Arrays

Single layer/few layer transition metal dichalcogenides(TMDs)is an important high mobility new channel material to replace silicon in the‘post Moore's law era'of integrate circuit industry.In this study,we choose a important member in the TMDs family:MoTe₂as the research material.On the one hand,MoTe₂owns a attractive characteristic:the same band gap(?1.1e V)as the silicon channel material.On the other hand,MoTe₂is significantly different from other TMDs that it owns variety of complex crystal phases,which can be easily synthesized at room temperature.This property realizes the preparation of high-performance and complex structure MoTe₂-based devices,gives it great potential in novel microelectronic device applications.In this work,a series of systematic and in-depth studies have been carried out on the controllable preparation,transfer and electrical properties of the CVD phase of the macro-MoTe₂nanoribbon array.Main results are as follows:First of all,the high-efficiency and pure phase MoTe₂nanoribbon array was successfully synthesized.Graphical Mo O₃precursor was firstly deposited on Si O₂substrate by shadow mask PVD method.A precisely controlled CVD process followed.The placement of the precursor substrate in the CVD growth process and the critical thickness of the precursor Mo O3 film,will effectively affect the crystal phase of the MoTe₂nanoribbon array.It was confirmed that the CVD process did not affect and destroy the size and shape of the Mo O₃precursor.A well control of the thickness,surface and crystal quality of the MoTe₂nanoribbon was eventually achieved;Secondly,the PVP/PVA assisted macro-scale MoTe₂nanoribbon array transfer printing process was successfully developed.By optimizing PVA concentration,spin coating speed and water bath removal time of PVP/PVA,the macro-scale transfer of2H-MoTe₂nanoribbon array,metal electrode/2H-MoTe₂nanoribbon array composite structure was effectively realized;it was found that 1T'-MoTe₂could be transferred100%by using Ag/Au and other metal electrode auxiliary methods,and the metal/1T'-MoTe₂composite structure electrode could be directly formed.The results show that the PVP/PVA seal transfer process is universal.The MoTe₂nanoribbon array can 100%transfer to Si O2,Si,Ge,Hf Al O₂,Zr O₂and other substrates macroscopically.Results show that the PVP/PVA transfer printing process will not destroy the properties or reduce the quality of the MoTe₂nanoribbon array,indicates high practical feasibility;Finally,the Au/1T'-MoTe₂/2H-MoTe₂/Hf Al O₂complex structure MOSFET transistor was successfully constructed.The results show that the polycrystalline2H-MoTe₂nanoribbons synthesized by CVD have p-type conductivity,and the high-k gate dielectric Hf Al O₂prepared by solution method has good quality.When the gate working voltage is between-3v to 3v,the leakage current density is maintained at 10^-7A/cm²,Au/1T'-MoTe₂composite electrode can effectively improve the contact resistance with 2H-MoTe₂nanoribbon.The mobility of Au/1T'-MoTe₂/2H-MoTe₂/Hf Al O₂structure MOSFET is close to 30 cm²v^-1s^-1on average,which is close to the best level of polycrystalline MoTe₂-based microelectronic device ever reported(32cm²v^-1s^-1).In conclusion,the CVD phase controllable preparation of macro MoTe₂nanoribbon array has been realized in this study.The macro transfer process with high efficiency,high throughput and high feasibility has been developed.The high-performance Au/1T'-MoTe₂/2H-MoTe₂/Hf Al O₂complex structure MOSFET device has been constructed.It established foundation for the industrial application of MoTe₂-based microelectronics devices in the‘post Moore's law era'of integrated circuits industries.