Synthesis Of MoTe₂ Thin Film And The Research On The Transport Properties Of The Thin Film Transistor

Transition metal dichalcogenides(TMDs)have attracted intense interest for developing ultra-scaled electronics and optoelectronics,by virtue of their attractive 2D layered structures and unique physical properties that are absent in their bulk counterparts.More excitingly,their 2D structures offer superior electrostatic controllability and exemptible short-channel effects,rendering TMDs promising candidates for future sub-10 nn complimentary metal-oxide-semiconductor(CMOS)devices.Monolayer MoTe2,with the narrowest direct bandgap of-1.1 eV among Mo-and W-based transition metal dichalcogenides,has attracted increasing attention as a promising candidate for applications in novel near-infrared electronics and optoelectronics.Realizing layer-controlled 2D lateral growth is an essential prerequisite for uniform thickness and property control over the large scale,while it is not successful yet.Here we report layer-by-layer growth of 2-inch wafer-scale continuous monolayer 2H-MoTe2 films on inert SiO2 dielectrics by molecular beam epitaxy.A single-step Mo-flux controlled nucleation and growth process is developed to suppress island growth.This process can be provided only at low deposition rate which enables surface migration and interdiffusion of adatoms to form isotropic structure before they cluster to larger immobile complexes.Atomically flat 2H-MoTe2 with 100%monolayer coverage is successfully grown on inert 2-inch SiO2/Si wafer,which exhibits highly uniform in-plane strutural continuity and excellent phonon-limited carrier transport behavior.The dynamics-controlled growth recipe is also extended to fabricate continuous monolayer 2H-MoTe2 on atomic-layer-deposited Al2O3 dielectric.We also demonstrated the phase transition from 2H to 1T' MoTe2 by controlling the growth temperature.A lot of characterizations were carried out to examine the large area and high quality properties of 2H-MoTe2 and 1T'-MoTe2.With the breakthrough in growth of wafer-scale continuous MoTe2 monolayers on device compatible dielectrics,batch fabrication of high-mobility monolayer MoTe2 thin film transistors(TFTs)and the three-level integration of vertically stacked monolayer MoTe2 transistor arrays for 3D circuitry are successfully demonstrated.Where a high current on/off ratio exceeding 107 is achieved in the monolayer MoTe2 thin film transistor with titanium contact which present P-type semiconductor behavior,and the hole mobility is demonstrated to be 23.4 cm2V-1s-1.There was no significant performance degradation during the 3D stacking process in the 1 St-layer TFTs.All three devices show strong gate modulation behaviors.Enhanced ?FE and on/off ratios were also revealved from the 2nd-and 3rd-layer devices.This work provides novel insights into the scalable synthesis of monolayer MoTe2 films on universal substrates and paves the way for the ultimate miniaturization of electronics.