Study On The Controllable Preparation And Properties Of Two-dimensional Van Der Waals Fe_1.125Te Crystals

As an emerging material,two-dimensional transition metal sulfide has thickness-dependent physical properties and creates an opportunity to form heterostructures of a variety of properties that combining with any two-dimensional layered materials.It is be expected to become the next generation of new materials in integrated circuits and has attracted much attention in microelectronics.In this paper,we choose Fe_1.125Te an important member of transition metal dichalcogenides(TMDs)as research object to carrying a series of study in magnetism and electricity.Fe Te is a room temperature tetragonal crystal with strong electronic correlation which extremely sensitive to the concentration of Fe.Fe_1.125Te single crystals are consists of excess Fe atoms inserted into the gap.Particularly the structural difference makes Fe_1.125Te that exhibit different properties in magnetic.The preparation of related spintronic devices is expected to realize its application value in microelectronic devices.This paper aim at the properties of Fe_1.125Te from the growth and preparation of single crystals to the thinning of bulk single crystals and the characterization of ferromagnetic and electrical properties.The main experimental contents and results are as follows:First,the Fe_1.125Te bulk single crystals were successfully synthesized by the molten salt method(Flux),additionally we explained that the relationship between the growth conditions and the size of the single crystal,what's more,we achieved the growth of a single millimeter-level bulk single crystal.It confirmed that the growth orientation of the single crystal crystal was plane for(00l).We can develop large-scale growth of high-quality single crystals.Second,we explained the relationship between the thickness and time of the liquid phase exfoliated single crystal and obtained ultra-thin nanosheets at 51 nm and 8 nm.Besides,by means of measuring the magnetic properties of the bulk and ultra-thin nanosheets,it found that as the thickness decreases the ferromagnetism increases and the magnetization axis changes from the in-plane magnetization of the block to the out-of-plane magnetization of the nanosheets.The hysteresis loop of the liquid phase stripped nanosheets has an exchange bias phenomenon.Additionally,we analyzed the internal mechanism of the thinning of the thickness of the magnetic axis and the exchange bias.Fascinatingly,the Curie temperature is greater than 400 K.Similarly,nanosheets with a range of thicknesses ranging from 13nm 54nm are obtained by mechanical exfoliation.Notably,it was indicated that the room temperature ferromagnetism by MFM magnetic force microscope.Separately,we explored the process of homogenization,photolithography,development,etching,electrode plating,photoresist removal,etc.and prepared the Hall device of Fe_1.125Te single crystal nanosheet.The Hall signals of the bulk and nanosheets prove that the electrons of Fe_1.125Te at low temperature are carriers and the holes at normal temperature are carriers revealing the changes in electron spin and charge caused by the phase transition of its structure.Furthermore,the measured resistivity of Fe_1.125Te is 346.9???cm.The stability test shows that it is prone to oxidation exposed to the air hence the micro-structured electronic devices need to be packaged.Finally,we explored the process of fabricating Fe_1.125Te/Al₂O₃/Py spintronic devices.