The Damage Effects Of CVD Single-layer MoS₂ Irradiated By Heavy Ions

Under the guidance and promotion of Moore's Law,the semiconductor industry has been growing rapidly for half a century.However,in recent years,with the continuous improvement of the process technology,Moore's Law began to face a challenge,that the 7nm is the physical limit of the preparation process.It also means that once the transistor process is smaller than this size,quantum tunneling effect will become a common problem for chip manufacturing.The monolayer MoS₂ has a suitable direct bandgap width?about 1.8 eV?with its high thermal conductivity,conductivity and high current switching ratio,which make it an important candidate semiconductor material for future nanostructures that may replace silicon.Therefore,it is meaningful to study the mechanism of ion damage and the morphological characteristics of defects in MoS₂ materials and devices,which helps to explore the application of MoS₂ devices and the cognition of the interaction between ion beam and ultra-thin layer materials.This work is mainly to study the effect of heavy ion on the irradiation damage of single layer MoS₂.The number of layers of MoS₂ prepared by CVD method was determined by optical microscopy and Raman spectroscopy.The monolayer MoS₂ prepared by CVD?chemical vapor deposition?under high energy 209Bi ion irradiation was analyzed by Raman analysis and AFM observation.And the results are compared and analyzed before and after the beam irradiation of single layer MoS₂ prepared by mechanical stripping method.The latent tracks induced by fast heavy ions in monolayer MoS₂ were observed by AFM.The average track yield was obtained by comparing the number of ions and the number of traces under the multi-field observation.The latent tracks appear mainly in the form of pits in the irradiated single layer of MoS₂,which are significantly different from the hillocks observed by the mechanical stripping method.Using Raman spectroscopy,it is observed that the peaks of MoS₂ E2g1 and A1g are obviously weakened with the increase of irradiation fluence,which is due to the adsorption of oxygen molecules with high binding energy in the air vacancy in the latent tracks,and free electrons are extracted in MoS₂.The Raman peaks corresponding to the vibrationsE2g1 of A1g phonons are gradually blue-shifted after irradiation.This is due to the formation of latent tracks defects,which will directly cause lattice deformation,the decrease of the surface stress and the decrease of the thermal conductivity.So the laser power in the Raman measurement makes the MoS₂ locally warming up,causing the blue shift of the whole peak.The electron-phonon coupling degree of E2g1 is much weaker than that of A1g,so the effect of different fluence on the peak position of the E2g1 model is small,namely the blue shift degree of the peak position is small.The Raman peak of the CVD sample is more sensitive to the radiation fluence than the mechanical stripping method.The overall blue shift of the peak position is smaller than the mechanical stripping method,which is due to the difference of preparation process.