Spin Injection Of High Mobility Senmiconductor Materials

The goal of spin electronics is the realization of information recording,manipulating,transporting,and storing etc,through themanipulationof spin properties of electrons in semiconductor or metal systems.The spin injection effect,as the core step to write and transfer information into semiconductors and metals,is one of the key technologies to research and developdevices ofsemiconductors and metal-based spin electrons.In this thesis,magnetic metal thin films or magnetic metal thin film/semiconductor composite materialswith different structures werefabricated by magnetron sputtering technique.Astructure of the three-port spin implant was prepared by means of micro-processing such as UV exposure.And its magnetic transport properties were systematically studied.The specific results are as follows:First,Ru(30nm)/Ta(10nm)/CoFeB(10nm)/InAs thin films were prepared on InAs substrates with high mobility,and non-local geometrical magnetoresistance(MR)was measured by the four-terminal method.Our results shows that the physical origin of nonlocal geometrical MRis the Lorentz force caused by the magnetic field.In the case of a high magnetic field,the Hall angle is close to 90 degrees and the current density is almost parallel to the interface of InAs/CoFeB,where the current is almost limited to transport in InAs.The specific form of transfering or scattering at the interface of spins in the system is studied by a simplifiedsystem of Ru(30nm)/Ta(10nm)/CoFeB(10mn)/InAs and the influence fromtransferredspinson transport properties inthe system.It results in anMRand flip magnetization states in the Ru(30nm)/Ta(10nm)/CoFeB(10mn)/InAs thin films.In addition,the resistivity of the semiconductor InAs is much higher,so the effect of MR in Ru(30nm)/Ta(10nm)/CoFeB(10nm)/InAsstructure will also be particularly significant.The MRversus magnetic field dependence of the devicein the linear MRregion can be increased from 12.6 T-1 of the local MRto 45.3 T-1 of the nonlocal MR.And the measured geometrical MRcan reach the order of 104%.These features are very attractive for the devices to be used in the field of high field sensors,this also provides new ideas for the design of high magnetic field detectors.Secondly,Pt(5mn)/Co(0.8nm)/AlOx(2nm)superparamagnetic films were grown on Si/SiO2(500nm)by magnetron sputtering.By controlling the polarity and size of the gate voltage,the progress of the Co redox reactioncan be easily controlled,thus the size of the superparamagnetic Co particles and the superparamagnetic properties of the filmscan also be controlled.It was found through XPS that the redox reaction of cobalt on the anode was adjustable.These findings provide a new approach to designing high-density,low-power,and nonvolatile new magnetic memory devices based on superparamagnetic thin films.At the same time,we have successfully injected spins into the wide bandgap semiconductor SiC through the Schottky junction.We measured the spin relaxation life of SiC up to 300 ps.Through the analysis of the transport mechanism,the carrier tunneling process in the Schottky junction is multi-step one.In amulti-step tunneling stage,the spin-polarized carriers can be capturedusing the defective states,and the unbalanced spins will relax in these defect states.Since the spin relaxation time of the body region is shorter than that of defective states,and the spin relaxation life of the defect state is more than 1 ns,this indicates that in order to accurately measure the spin relaxation life of the body region,the transport process of interface states should be avoided as much as possible.The spin relaxation life measured in the direct tunneling process reflects the intrinsic properties of semiconductor materials.Finally,in order to study the photoelectric properties of semiconductor devices,we designed and integrated the light field generation and response devices in nanometer pattern and ultra-wideband magnetoelectricity measurement systems.The device can introduce thelight of various wavelengths into the cavity of the scanning electron microscope.For a basic electron beam exposure system without a magnetic field,an electric field and a probe system,the introduction of the light field is very simple.However,when the above three subsystems,especially the magnetic field generating devices and the probe systems,are integrated into the cavity,it is very difficult to introduce the light field through a new probe.It should also be noted that although afiber is very thin,but the fiber head is relatively thick,so that theprobe to guide the fiber will be relatively stout,thus it needsanecessary mechanical strength to support the fiber head.In the concrete realization of the system,in order to save space,we skillfullyfixed the fiber head on the magnetic pole of the magnetic field generating device.This design,on the one hand,ensures the mechanical strength required to secure the fiber head;on the other hand,it is possible to introduce a lightbeam into the middle of the sample tablebecause the magnetic poles of the magnetic field generating device are placed in the center of the sample table in the working state;Furthermore,this can greatly save thevaluable cavity space.It can be described as kills three birds with one stone.The above workhas developed a new idea for the research and development of semiconductor spin electronic devices,new magnetic sensors and magnetic memory devices,andprovides an analysis andproof atphysical image level and laysa physical foundation for the furtherresearch and development.