High Curie Temperature Achieved in the Ferromagnetic MnxGe1-x/Si Quantum Dots Grown by Ion Beam Co-Sputtering.

Xiaoxiao Duan,Chunjiang Lu,Shuming Ye,Jie Yang,Xinpeng He,Chen Li,Chong Wang,Haoyang Cui,Rongfei Wang,Luran Zhang,Feng Qiu,Jing Yang

doi:10.3390/nano12040716

Xiaoxiao Duan, Chunjiang Lu + Show 10 more

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https://doi.org/10.3390/nano12040716

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Abstract

Ferromagnetic semiconductors (FMSs) exhibit great potential in spintronic applications. It is believed that a revolution of microelectronic techniques can take off, once the challenges of FMSs in both the room-temperature stability of the ferromagnetic phase and the compatibility with Si-based technology are overcome. In this article, the MnxGe1−x/Si quantum dots (QDs) with the Curie temperature (TC) higher than the room temperature were grown by ion beam co-sputtering (IBCS). With the Mn doping level increasing, the ripening growth of MnGe QDs occurs due to self-assembly via the Stranski–Krastanov (SK) growth mode. The surface-enhanced Raman scattering effect of Mn sites observed in MnGe QDs are used to reveal the distribution behavior of Mn atoms in QDs and the Si buffer layer. The Curie temperature of MnxGe1−x QDs increases, then slightly decreases with increasing the Mn doping level, and reaches its maximum value of 321 K at the doping level of 0.068. After a low-temperature and short-time annealing, the TC value of Mn0.068Ge0.932 QDs increases from 321 K to 383 K. The higher Ge composition and residual strain in the IBCS grown MnxGe1−x QDs are proposed to be responsible for maintaining the ferromagnetic phase above room temperature.

Highlights

In the last two decades, massive efforts have been devoted to probing one kind of multifunctional material, on which the so-called three golden disciplines, namely, optics, microelectronics, and magnetism, can be integrated organically, so that the optical, electronic, and magnetic responses can be modulated effectively in one kind of material by the external fields [1,2]
The composite Ge-Mn target can be manufactured by pasting a certain amount of purity Mn slices onto a single crystal Ge target and the Mn doping level x in the Mnx Ge1−x high purity Mn slices onto a single crystal Ge target and the Mn doping level x in the
Combined with the observation of AFM, Raman, and X-ray photoelectron spectroscopy (XPS), the composition and structure transition of quantum dots (QDs) mainly occurs at the interface between the island bottom and the Si buffer, from the MnGe QDs, MnGeSi QDs, to MnGeSi QDs accompanied by a small quantity of precipitate, with an increase in the Mn doping level

Summary

Introduction

In the last two decades, massive efforts have been devoted to probing one kind of multifunctional material, on which the so-called three golden disciplines, namely, optics, microelectronics, and magnetism, can be integrated organically, so that the optical, electronic, and magnetic responses can be modulated effectively in one kind of material by the external fields [1,2] If it actualizes a new information technology, the spin electron substitutes for the charge as the information carrier, characterized by ultrafast transportation, high-capacity, ultra-wideband, and ultralow-power dissipation [1,3,4]. The low dimensional DFMS with a TC value above room temperature has been demonstrated recently in other nanostructures, such as nanowires and nanotubes [14,15]. Mn-doping-level dependent ferromagnetic evolution of these DFMS QDs is addressed well

Experimental Section

Results and Discussion

Statistic histograms forfor thethe diameter of of thethe

Conclusions