Addimer chain structures: Metastable precursors to island formation on Ge-Si(0 0 1)-(2 × n) alloyed surface |
| |
Authors: | Kyle J Solis BS Swartzentruber |
| |
Institution: | a Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131, United States b Computer Science Department, University of New Mexico, Albuquerque, NM 87131, United States c Sandia National Laboratories, Albuquerque, NM 87185, United States |
| |
Abstract: | We have identified addimer chain structures as metastable precursors to compact epitaxial islands on the (2 × n) reconstructed SiGe wetting layer, using polarity-switching scanning tunneling microscopy (STM). These chain structures are comprised of 2-12 addimers residing in the troughs of neighboring substrate dimer rows. The chain structures extend along equivalent 〈1 3 0〉 directions across the substrate dimer rows in a zigzag fashion, giving rise to kinked and straight segments. We measure a kink-to-straight ratio of nearly 2:1. This ratio corresponds to a free energy difference of 17 ± 4 meV, favoring the formation of kinked segments. The chain structures convert to compact epitaxial islands at elevated temperatures (?90 °C). This conversion suggests that the chain structures are a precursor for compact island formation on the SiGe wetting layer. We digitally process filled- and empty-state STM images to distinguish chain structures from compact islands. By monitoring the populations of both species over time, the chain-to-island conversion rates are measured at substrate temperatures ranging from 90 to 150 °C. The activation energy for the conversion process is measured to be 0.7 ± 0.2 eV with a corresponding pre-exponential factor of 5 × 104±2 s−1. |
| |
Keywords: | Addimer chain structures Compact epitaxial islands C-dimer Polarity-switching scanning tunneling microscopy (2 × n) Silicon-germanium alloy surface kinetics |
本文献已被 ScienceDirect 等数据库收录! |
|