Direct Growth Of Non-vander Waals Magnetic Materials Cr₂x₃（X= S,Se,Te） On SiO₂/Si Through The Promotion Of KOH

With the continuous development of science and technology,people’s demand for electronic devices continues to increase,and electronic devices are also developing towards smaller size,more energy saving and larger capacity.Electron spin devices have these advantages,and two-dimensional magnetic materials provide great development prospects for electron spin devices.This is because two-dimensional magnetic materials have some physical properties that their bulk materials do not have,such as good mechanical flexibility,and they are still magnetic at the limit thickness.The current Cr₂S₃,Cr₂Se₃and Cr₂Te₃have attracted the interest of researchers.These materials usually require bottom-up synthesis methods such as chemical vapor deposition（CVD）methods.Because they are non-van der Waals materials,the growth substrate usually requires an inert surface such as mica,and complex transfer steps to SiO₂/Si are required for device construction and magnetic characterization,which can lead to sample damage and contaminationn.Therefore,it is significance to modify the surface of SiO₂/Si to make non-vdw materials grow directly.Based on this,we use KOH to treat the surface of the SiO₂/Si substrate and change the formation energy between the material and the substrate,and test its properties with probe platform and an physical property measurement system（PPMS）.The work mainly includes the following:（1）The SiO₂/Si substrates were spin-coated with KOH and we used chemical vapor deposition（CVD）to prepare Cr₂S₃,Cr₂Se₃and Cr₂Te₃nanosheets and determine their structures through Raman,XRD,XPS characterization.Thin layer and large area R-3 space group Cr₂S₃,R-3 space group Cr₂Se₃and Cr₂Te₃of p31c space group were successfully prepared on the SiO₂/Si substrate.（2）The field effect transistor（FET）was constructed by lithography and evaporation,and the electrical measurement of Cr₂S₃and Cr₂Se₃showed that Cr₂S₃is n-type semiconductor,and Cr₂Se₃is metallicity.The magnetic properties of Cr₂S₃,Cr₂Se₃and Cr₂Te₃grown on SiO₂/Si surface were directly characterized by physical properties measurement system（PPMS）.It was found that Cr₂S₃is ferromagnetic,Cr₂Se₃is spin glass,and Cr₂Te₃is ferromagnetic.（3）To further understand the role of KOH in the reaction process,we conducted a control experiment on KOH-assisted Cr₂S₃growth and used density functional theory calculation to verify the conjecture.Experiments and calculations show that K ions in KOH play an auxiliary role in the growth of Cr₂S₃,which makes the growth morphology of Cr₂S₃on the surface of silica more regular.OH ions play a major role in promoting Cr₂S₃to grow larger and thinner on the surface of silica.This method provides a new idea for the growth of non-van der Waals magnetic materials,simplifies the steps of transistor construction and magnetic measurement of non-magnetic materials,and provides a brief and fast material growth method for the field of spintronic devices.