Growth and characterization of Ge nanostructures selectively grown on patterned Si

Abstract

By utilizing different distribution of strain fields around the edges of oxide, which are dominated by a series of sizes of oxide-patterned windows, long-range ordered self-assembly Ge nanostructures, such as nano-rings, nano-disks and nano-dots, were selectively grown by ultra high vacuum chemical vapor deposition (UHV-CVD) on Si (001) substrates. High-resolution double-crystal symmetrical omega/2 theta scans and two-dimensional reciprocal space mapping (2D-RSM) technologies employing the triple axis X-ray diffractometry have been used to evaluate the quality and strain status of as-deposited as well as in-situ annealed Ge nanostructures. Furthermore, we also compare the quality and strain status of Ge epilayers grown on planar unpatterned Si substrates. It was found that the quality of all Ge epitaxial structures is improved after in-situ annealing process and the quality of Ge nano-disk structures is better than that of Ge epilayers; on planar unpatterned Si substrates, because oxide sidewalls are effective dislocation sinks. We also noted that the degree of relaxation for as-deposited Ge epilayers on planar unpatterned Si substrates is less than that for as-deposited Ge nano-disk structures. After in-situ annealing process,all Ge epitaxial structures are almost at full relaxation whatever Ge epitaxial structures grew on patterned or unpatterned Si substrates. (c) 2008 Published by Elsevier B.V.