| It is well known that electronic devices fabricated by traditional thin-film preparation processes have inherent interface defects,while two-dimensional magnetic materials discovered in recent years have the characteristics of atomic-scale flat film quality and monolayer magnetic order.This not only provides an optimal solution for solving the interface defect problem of traditional thin-film devices,but also is expected to realize the fabrication of electronic devices with lower energy consumption and higher efficiency.Among many two-dimensional magnetic materials,Fe3GeTe2 material stands out due to its unique and excellent characteristics-it is two-dimensional magnetic metal material with topological ferromagnetism.The nanometer-thick Fe3GeTe2 film is ferromagnetic,has a large coercivity,and has a remarkable anomalous Hall effect,so its Hall resistance can be measured directly through electrical transport.Fe3GeTe2 material not only has the above excellent properties but also has a higher Curie temperature(bulk material Tc=230 K)and stronger perpendicular magnetic anisotropy(～107 erg/cm3)compared with other two-dimensional magnetic materials.This makes it a preferred material for the fabrication of magnetic tunnel junctions and magnetic random-access memory devices based on current-induced switching.Based on the excellent magnetic properties of the two-dimensional magnetic material Fe3GeTe2,this thesis takes Fe3GeTe2 as the main research object to study the single-crystal bulk of growth conditions,morphology characterization,structural analysis,bulk magnetic measurement,thin film preparation,and device machining.Moreover,we studied the Hall effect of Fe3GeTe2 thin film in detail.First,we compared and explored the growth methods of Fe3GeTe2 bulk materials and various growth conditions,and finally obtained Fe3GeTe2 materials of excellent quality.We used the flux method and chemical vapor transport method to grow Fe3GeTe2 bulk materials respectively.After analyzing the X-ray diffraction patterns of the obtained bulk samples,we determined that the chemical vapor transport method is the best growth method.Subsequently,we changed the growth conditions such as temperature and time,compared and analyzed the obtained samples in terms of composition and magnetic properties.We believe that in the preparation process of Fe3GeTe2 bulk material,the main factor affecting the crystallization quality of Fe3GeTe2 is crystallization temperature,and the length of crystallization time almost only affects the quantity and volume of Fe3GeTe2 material.By comparing the Fe3GeTe2 materials prepared under different conditions above,we analyzed and optimized the growth method and growth conditions of Fe3GeTe2 bulk materials.Finally,we think that the chemical vapor transport method could be used to grow Fe3GeTe2 single crystal samples with a flat and clean surface,a clear layered structure,and a large volume.Second,we characterized the morphology of the prepared Fe3GeTe2 single crystal samples and performed magnetic measurements on their bulk samples by superconducting quantum interference device.We characterized the surface morphology and layered structure of the samples under a scanning electron microscope at extremely high magnification,and the results proved that the samples we grew were of extremely high quality again.Since the two-dimensional magnetic material has a large contact area with the air on the plane,we considered the influence of oxidation on the Fe3GeTe2 single-crystal bulk and thin film.We analyzed the effects of the oxidation in Fe3GeTe2 on its properties,especially on magnetic properties by Raman spectroscopy and other methods.Finally,we fabricated Fe3GeTe2 thin films and measured their Hall signals.We used electron beam exposure technology to accurately process the Fe3GeTe2 film obtained by mechanical stripping method,so that the Hallbar can be accurately covered the Fe3GeTe2 film.Subsequently,we measured its Hall signal and analyzed the factors that may affect its magnetic properties.It will have a good preparation for the preparation of spintronic devices based on Fe3GeTe2 by micro-nano processing. |
PDF Full Text Request