Te doping effects on the ferromagnetic performance of the MnGe/Si quantum dots grown by ion beam sputtering deposition

Abstract

Dilute magnetic MnGe quantum dots (QDs) have been a popular research topic due to their great potential application on spintronics and their natural compatibility with today's highly developed silicon-based complementary metal oxide semiconductor (CMOS) technology. However, the relatively low Curie temperature impedes their ability to maintain the ferromagnetic phase and creates difficulty for their practical application in spintronics at room temperature. Here, we report the first preparation of the Te-doped dilute-magnetic Mn0.064Ge0.895Te0.041/Si QDs by using the ion beam composite target sputtering technique. Growth temperature and deposition thickness dependent QDs density and magnetic properties were investigated systematically. The experimental results indicate that the QD density of Mn0.064Ge0.895Te0.041/Si sample increases first and then reduces with the deposited thickness, while the QDs' diameters increase monotonously from 10.18 ± 0.21–33.6 ± 0.34 nm. Curie temperature of 369 K observed in Mn0.064Ge0.895Te0.041 QDs is higher than that of 295 K observed in Mn0.061Ge0.939 counterparts grown at the same conditions. Correspondingly, the saturation and residual magnetization in the former are much higher than in the latter. The ferromagnetic enhancement can be attributed to that the nonpolar Mn0.064Ge0.936 QDs transform into Rashba polar Mn0.064Ge0.895Te0.041 QDs with the doping of Te ions, which obviously promotes the exchange coupling between holes and Mn atoms. Our work provides a practical approach for improving the ferromagnetism and Curie temperature of silicon-based diluted magnetic semiconductor QDs.