Abstract
Mn0.05Ge0.95 quantum dots (QDs) samples were grown by molecular beam epitaxy on Si substrates and 15-nm-thick fully strained Si0.8Ge0.2 virtual substrates, respectively. The QDs samples grown on the Si0.8Ge0.2 virtual substrates show a significant ferromagnetism with a Curie temperature of 227 K, while the QDs samples grown on the Si substrates are non-ferromagnetic. Microstructures of the QDs samples were characterized by high resolution transmission electron microscopy and synchrotron radiation X-ray diffraction. Interdependence between microstructure and ferromagnetism of Mn-doped Ge QDs was investigated. For the QDs sample grown on the strained Si0.8Ge0.2 virtual substrate, although the ferromagnetic phase Mn5Ge3 clusters were found to be formed in small dome-shaped dots, the significant ferromagnetism observed in that sample is attributed to ferromagnetic phase Mn-doped large dome-shaped Ge QDs, rather than to the ferromagnetic phase Mn5Ge3 clusters. The fully strained Si0.8Ge0.2 virtual substrates would result in a residual strain into the QDs and an increase in Ge composition in the QDs. Both consequences favor the formations of ferromagnetic phase Mn-doped Ge QDs from points of view of quantum confinement effect as well as Mn doping at substitutional sites.
Highlights
Mn0.05Ge0.95 quantum dots (QDs) samples were grown by molecular beam epitaxy on Si substrates and 15-nm-thick fully strained Si0.8Ge0.2 virtual substrates, respectively
For the QDs sample grown on the strained Si0.8Ge0.2 virtual substrate, the ferromagnetic phase Mn5Ge3 clusters were found to be formed in small dome-shaped dots, the significant ferromagnetism observed in that sample is attributed to ferromagnetic phase Mn-doped large dome-shaped Ge QDs, rather than to the ferromagnetic phase Mn5Ge3 clusters
The fully strained Si0.8Ge0.2 virtual substrates would result in a residual strain into the QDs and an increase in Ge composition in the QDs
Summary
Liming Wang,[1] Tao Liu,[1] Quanjie Jia,[2] Zhi Zhang,[3] Dongdong Lin,[1] Yulu Chen,[1] Yongliang Fan,[1] Zhenyang Zhong,[1] Xinju Yang,[1] Jin Zou,[3] and Zuimin Jiang1,a 1State Key Laboratory of Surface Physics, Department of Physics, and Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433, China 2Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Beijing 100039, China 3Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, Queensland 4072, Australia (Received January 2016; accepted March 2016; published online 7 April 2016) Mn0.05Ge0.95 quantum dots (QDs) samples were grown by molecular beam epitaxy on Si substrates and 15-nm-thick fully strained Si0.8Ge0.2 virtual substrates, respectively.
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