Co Sputtering Growth Mechanism And Magnetic Properties Of Mn_xGe_1-x/Si Quantum Dots With High Doping Rate

In the past two decades,diluted magnetic semiconductor(DMS),as a research hotspot of material science,has shown excellent performance and good application prospects.DMS can significantly improve the performance of the device,and reduce the size and power consumption of the device by introducing electronic spin into the traditional semiconductor materials.Among many types of DMS materials,MnGe DMS is not only compatible with traditional Si based semiconductor technology,but also can produce spin electronic devices with room temperature ferromagnetic properties with high Curie temperature(T_C)through strict process control.Therefore,the research on MnGe ferromagnetic semiconductors has aroused great interest in academia and industry.In thesis,a series of MnGe quantum dots with different doping concentrations were prepared by ion beam sputtering(IBS).Firstly,the surface of Si substrate is deeply cleaned by the standard Shiraki method,so as to create excellent surface morphology for quantum dots nucleation.Secondly,the growth temperature and deposition parameters of Mn_xGe_1-x quantum dots were controlled by the control variable method.The process parameters of growth temperature and Ge deposition thickness with the best magnetic properties were obtained..The surface enhanced Raman scattering from Mn nanostructures was observed in Mn_x Ge_1-x quantum dots.It is also observed that the Ge crystal peak strength of Raman scattering increases with the increase of roughness measurement of the Surface(RMS)and particle size.The distribution behavior of Mn atoms in quantum dots and Si buffer layer is revealed.Five kinds of Mn_xGe_1-x quantum dots with different doping concentrations of 0%,4.8%,5.9%,7%and 7.8%were prepared by co-sputtering.With the increase of doping concentration,the Curie temperature of Mn_xGe_1-x QDs increased first and then decreased.The T_C value of Mn_0.07Ge_0.93 QDs increased from 313 K to 337 K after short-time low-temperature annealing.At last,the reason of Curie temperature drop of high doping concentration 7.8%is analyzed,and a complete set of preparation technology is summarized.