The influence of a Pb surfactant on Mn delta-doped layers on Si(001)

The high growth temperatures normally required for MBE growth of Si pose a challenge for the growth of dilute magnetic semiconductors based on Si. With the use of a Pb surfactant, we can drop the growth temperature of Si(001) below 200$^{o}$C, while preserving epitaxial growth, as shown by RHEED and TEM. The Pb surfactant also influences how a single Mn delta-doped layer grows on Si(001). ~For 0.7 monolayer Mn deposition onto Pb/Si(001), RBS/channeling measurements show that 25{\%} of the Mn occupies a substitutional-like site. This fraction increases with decreasing Mn concentration. Polarization-dependent XAFS measurements suggest that the samples grown without Pb exhibit a CsCl-like structure. XAFS results for 0.7 ML Mn on Pb/Si(001) differ from growth without Pb, with 2 types of Si neighbors at short (in-plane) and long Mn-Si distances and a ratio of coordination numbers comparable to the RBS results.