Preparation Of Fe_2³N Thin Films By Magnetron Sputtering And Effect Of Deposition Temperature On Their Magnetoelectric Properties

Spintronics is an interdisciplinary study that exploits electron spins to design new devices.Compared with traditional semiconductor devices,spintronic devices have the advantages of high integration,good stability,and fast processing speed.However,the choice of spin-injection layer material for spintronic devices has been an intractable problem.With further research,Fe-N compounds have attracted the attention of researchers because of their rich magnetoelectric properties with various phase structures.Among these phase structures,?-Fe_2³N has the following two advantages:First,?-Fe_2³N can regulate its properties by changing the ratio of Fe and N.Secondly,?-Fe_2³N can be deposited on the GaN substrate to form an?-Fe_2³N/GaN heterostructure.As well known,GaN is an important material for the development of new electronic devices,and is called the third-generation semiconductor.Therefore,the all-nitride heterostructure of?-Fe_2³N/GaN has broad application prospects.In order to study the effect of deposition temperature on the magnetoelectric properties of?-Fe_2³N films in?-Fe_2³N/GaN heterostructures.In this paper,Fe_2³N films were prepared on GaN?0001?substrates by DC magnetron sputtering at different deposition temperatures?25°C,150°C,275°C,400°C?,and X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?,Raman spectroscopy,hysteresis loop,M-T curve,field cooling/zero field cooling and variable temperature resistivity curve of the samples were further tested.Through the analysis of the characterization results,the main conclusions obtained are as follows:?1?In the samples at all deposition temperatures,the amorphous phase and the crystalline phase of?-Fe_2³N coexist.The amorphous phase of?-Fe_2³N is dominant in the sample deposited at25°C.With the increase of deposition temperature,the crystallinity of?-Fe_2³N film increases gradually,and the ratio of Fe:N decreases.In the deposition temperature of this experiment,400°C is favorable for forming a single-phase?-Fe_2³N?002?film.?2?It can be seen from the hysteresis loop that all samples exhibit ferromagnetism at room temperature.The saturation magnetization of the sample gradually increases as the deposition temperature increases because the crystal quality of the film increases as the deposition temperature increases.The coercivity of the sample decreased with increasing deposition temperature at the 5 K test temperature and hardly changed at the 300 K test temperature.By fitting the M-T curve,the Curie temperature of all samples was much greater than room temperature.The results of field cold/zero field cooling?FC/ZFC?show that the magnetic ground state of the sample is spin glass state;the irreversible temperature increases with the increase of deposition temperature,and the freezing temperature increases first and then decreases with the increase of deposition temperature.?3?It is known from the electrical characterization results that the resistivity of the sample deposited at 25°C showed the behavior of the semiconductor as a function of test temperature,while other samples exhibits metallic behavior at low temperatures and exhibits semiconductor behavior at high temperatures.This property is a result of the interaction of the resistance of the crystalline phase of Fe_2³N and the resistance of the amorphous phase of Fe_2³N.It can be seen from the analysis that the resistivity of the sample is dominated by the crystalline phase Fe_2³N at low temperatures,and the amorphous phase Fe_2³N is dominant at high temperatures.By fitting the experimental results,we further found that the resistivity of the crystalline phase of the Fe_2³N film is derived from the residual resistivity,the resistivity caused by electron-electron scattering,the resistivity caused by the disordered local magnetic moment,and resistivity caused by the electrons-phonon scattering,and the resistivity of the Fe_2³N film of the amorphous phase is derived from the local electronic state caused by disorder.In addition,all samples have a large negative temperature coefficient of resistance,which can be applied to the field of the electronics industry,such as uncooled bolometers with low resistivity.