Surface Oxidation And Controllable Doping Techniques For Two-dimensional Materials

The rapid development of integrated circuits has led to updating of semiconductor materials and manufacture.Researchers have also paid attention on the gate dielectric materials of MOS devices.The conventional SiO₂gate oxide layer has gradually failed to meet the needs of device size reduction.The uniform growth of high-k oxides on the surface of two-dimensional materials as gate oxide media and controllable doping of two-dimensional materials is critical for the manufacture of 2D-based electronic and optoelectronic devices.The back-gate structure is widely used in the manufacture of two-dimensional ma-terial FETs at home and abroad.This structure uses the entire silicon dioxide on the Si substrate as the gate oxide layer,which is not conducive to integration,and can not achieve controllable doping.The two-dimensional material MOS tube based on the top gate structure is faced with problems such as large leakage current due to size reduction and small carrier mobility.At present,the method for dealing with the top gate struc-ture problem is to select a high-k medium such as HfO₂,Al₂O₃for the gate oxide layer.However,the transition metal oxide(TMO)produced by the surface of the air-contact transition metal disulfide(TMD)is unevenly wave-packed,resulting in poor interface quality of TMO/TMDs.PVD,CVD,etc.are commonly used in the preparation of oxide thin films in existing semiconductor processes.However,there are significant mechanical stresses at the interface between the oxide and the substrate prepared by these methods,and two-dimensional materials with a thick atomic layer thickness are generated during the deposition process.Non-negligible lattice damage.In addition to the problem of depositing ultra-thin oxide films on two-dimensional materials,the devices with back-gate structure FET structures have limited electrostatic regulation capabilities in terms of controllable doping in the fabrication of devices based on two-dimensional materials.Top Gate Structure In order to improve the mobility of carriers,an insulating two-dimensional material such as h-BN is usually used as the gate oxide layer.However,this method has problems such as difficulty in obtaining materials,uncertainty in film size and quality,and the like.In this paper,the main contributions and innovations of this paper are as follows:1.We select the HfSe₂material in this experiment,owing to its bandgap is similar to that of silicon and its oxide has a high dielectric constant.There are many difficulties in directly growing the gate oxygen layer on a two-dimensional material such as HfSe₂,which is easily oxidized in the air.In this project,the oxygen plasma treatment method was first used to remove the wave-shaped oxides generated from the surface of the HfSe₂material by oxidation by air moisture.On the basis of removing the oxide on the surface of the HfSe₂material,the oxidation was continued to be controlled,and the plasma bond discharge process was used to open the chemical bond on the surface of the HfSe₂sample to grow the corresponding lattice-matched oxide HfO₂.2.We have proved to use plasma treatment HfSe₂to prepare a dense,high atomic level flat k HfO₂film by utilizing optical microscopy,atomic force microscopy,XPS measurement spectrum,Raman spectroscopy and other methods.Compared with the nat-ural oxidation of HfSe₂exposed in the air,it is proved that the HfO₂film prepared by our proposed method can also be used as an effective passivation protective layer,which can prevent the underlying HfSe₂sample from being continuously affected by moisture in the air.Oxidation.3.Using the principle of intercalation technology,the intercalation material and the two-dimensional material atomic structure combine to exhibit unique properties such as high conductivity and catalytic effect.We have prepared a new type of ionic liquid intercalated multilayer graphene device structure to achieve controlled doping of two-dimensional materials.In the case of a small bias voltage range,the Fermi level can be shifted by several e V(about 2|E_F|up to 2.3e V),and the regulation of the intercalation technology is reversible,which can be stable in the air.And also could be repeated many times.This reflects the effectiveness of doping control of intercalation technology.It provides an exploration of a device structure with stronger control ability and better per-formance for two-dimensional material applications and optoelectronics and electronic devices.4.After the ionic liquid enters the gap of the multilayered graphene layer,the infrared emissivity of the graphene on the surface was adjusted from 0.57 to 0.41,and the relative reflectivity R_v/R₀increased from 1.0 to 1.15,and the G peak in the Raman spectrum appeared increasing,and the characteristic peak intensity was enhanced.Also,the sheet resistance was reduced from 11?/to 4?/.These methods make the intercalation based device exhibit better electrical,optical,and thermal characteristics.