Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Formation of Ge-Sn nanodots on Si(100) surfaces by molecular beam epitaxy | Mashanov et al. Nanoscale Research Letters 2011 6 85 http content 6 1 85 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Formation of Ge-Sn nanodots on Si 100 surfaces by molecular beam epitaxy 1 1 1 1 1 Vladimir Mashanov Vladimir Ulyanov Vyacheslav Timofeev Aleksandr Nikiforov Oleg Pchelyakov Ing-Song Yu2 Henry Cheng2 Abstract The surface morphology of Si 100 heterostructures grown at temperatures from 250 to 450 C by atomic force microscopy AFM and scanning tunnel microscopy STM ex situ has been studied. The statistical data for the density of nanodots ND depending on their lateral size have been obtained. Maximum density of ND 6 X 1011 cm-2 with the average lateral size of 7 nm can be obtained at 250 C. Relying on the reflection of high energy electron diffraction AFM and STM it is concluded that molecular beam growth of Ge1-xSnx heterostructures with the small concentrations of Sn in the range of substrate temperatures from 250 to 450 C follows the Stranski-Krastanow mechanism. Based on the technique of recording diffractometry of high energy electrons during the process of epitaxy the wetting layer thickness of films is found to depend on the temperature of the substrate. Introduction Self-assembled Ge-Sn nanodots ND are considered to be a possible candidate for direct band gap materials and have high potential for a variety of applications due to their compatibility with Si technology 1 2 . Ge-Sn ND have been grown on Si substrates by methods of molecular beam epitaxy MBE covered with ultrathin SiO2 films 3 4 . A quantum-confinement effect in individual Ge1-xSnx ND on Si 111 surfaces covered with ultrathin SiO2 films was observed using scanning tunneling spectroscopy at room temperature 5 . Strong photoluminescence from Si-capped Ge1-xSnx ND on Si 100 surfaces has also been observed by Nakamura et al. 3 . The epitaxial growth of Ge1-xSnx alloys is complicated
