Surfactant-mediated growth of ferromagnetic Mn delta-doped Si

Article

关键词: EPITAXIAL-GROWTH;    ELECTRONIC-STRUCTURE;    MANGANESE SILICIDE;    PB;   

DOI  :  10.1103/PhysRevB.88.174419

来源: SCIE

【 摘 要 】

We present an investigation of Mn delta-doped layers in Si(001) grown by molecular beam epitaxy. We discovered that a Pb surfactant has significant effect on the structural and magnetic properties of the submonolayer of Mn, which depends on the Si capping layer growth temperature T-Si, and the Mn coverage theta(Mn). The results presented in this paper identify three regions in the growth-phase diagram characterized by distinct magnetic behaviors and crystal structures. In one region, x-ray absorption fine structure and transmission electron microscopy experiments indicate that MnSi nanocrystallites form with B2-like crystal type structures. At the optimal growth conditions, T-Si = 200 degrees C and theta(Mn) = 0.26 monolayer, a ferromagnetic phase develops with a Curie temperature T-C > 400 K and a saturation moment m(sat) = 1.56 mu(B)/Mn, whereas T-C drops to zero for a control sample prepared without Pb. For T-Si > 200 degrees C MnSi-B20 type precipitates form with a T-C approximate to 170 K. Rutherford backscattering spectrometry shows that the increase in the remanent magnetization in these two phases is possibly correlated with an increase in the Mn substitutional fraction, which suggests that a Si1-xMnx dilute magnetic semiconductor may be forming in the matrix between the precipitates. Density functional calculations show that Pb changes the pathway by which the Mn atoms access the Si substitutional sites, MnSi. While the Pb increases the formation energy of Mn-Si at the Si surface, it enables substitutional incorporation by lowering the formation energy of Si vacancies by 0.92 eV.

【 授权许可】

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