Study Of Structure And Properties Of Mn_xGe_1-x/Graphene Quantum Dots Prepared By Co-Sputtering

Since graphene was discovered at the beginning of the 21st century.Graphene continues to grow in the field of spin electromagnetics.Studies have shown that the growth of Mn_xGe_l-x quantum dots on graphene can combine advantages of the ferromagnetism of dilute magnetic semiconductors with the graphene's ultra-high carriers to prepare spintronic devices with high Curie temperatures.The experimental process of this paper is to transfer graphene to SiO₂substrate.Using SiO₂substrate as the base,sputtering growth of Mn_xGe_l-xquantum dots in ion rapid sputtering equipment.A large amount of experimental data is used to analyze the influence of different factors on the morphology,crystallinity,valence and magnetic properties of Mn_xGe_1-x/graphene quantum dots.1.In order to explore the effects of temperature,Mn doping concentration,and Mn Ge deposition thickness on the surface morphology,valence bond and crystallinity of Mn_0.07Ge_0.93 quantum dots.Find out the best deposition temperature,Mn doping concentration,Mn Ge deposition thickness.In this paper,a large number of systematic experiments have been carried out.Before the experiment,the Mn Ge deposition thickness and Mn doping concentration were controlled,and the growth temperature range was designed from low to high.Finally,it was found that the morphology and crystallinity of the sample at 500?are better than those at other temperatures.In addition,AFM,Raman,and XPS were performed on the sample at 500?,and it was found that the appropriate temperature can make the size and density of the quantum dots on the sample surface uniform.At the same time,it is found that the valence states of Mn and Ge in the sample are both low valence states,and there is no high valence Mn Ge precipitation at the current temperature.Then,based on 500?,the experiment in the same section was carried out under the condition of constant Mn doping concentration.The structure of the sample,prepared with different Mn Ge deposition thicknesses,was characterized by AFM,Raman,etc.It is confirmed that the 6 nm Mn_0.07Ge_0.93 thin film sample deposited at 500?is superior to other samples in terms of morphology roughness and size uniformity.On the basis of the previous two sections,Mn_xGe_1-x/graphene quantum dot samples were prepared using co-sputtering targets with Mn doping concentrations of 0.06,0.07,and 0.078,and the three successfully prepared samples were subjected to AFM and Raman,XPS test,comparing the three samples,it is found that the sample with Mn doping concentration of 0.07 is the best in terms of morphology and crystallinity.The analysis found that when low Mn concentration is doped,due to the low Mn content,the diffusion ability of Mn on the surface of the sample is poor,which makes the prepared sample poor in morphology and crystallinity.However,when the Mn doping concentration is too high,XPS characterization shows that high-valence Mn and Ge elements appear in the sample,that is,the structure of the second phase.2.Finally,the Mn doping amount x is 0.06(Mn_0.06Ge_0.94 QDs),0.07(Mn_0.07Ge_0.93 QDs)and 0.078(Mn_0.078Ge_0.922 QDs)Mn_xGe_1-x/graphene quantum dot samples.The magnetic measurement was carried out and it was found that there are obvious remanence and coercivity in the three samples.In addition,the thermomagnetic curve test was carried out on them and the corresponding Curie temperatures were estimated to be 264,349 and 306 K respectively.