Observation of Ge surface segregation during Si-MBE on Ge/Si(001) probed by Si-H/Ge-H surface vibrations

The dimer composition on the Ge-segregated surface of a MBE-grown Si-layer/ Ge/Si(001) structure was investigated using surface infrared (IR) spectrosc opy on Si substrates with a buried metal layer (BML). The Ge-segregated sur face was modified by atomic hydrogen in order to visualize dimer compositio n by IR spectroscopy. When the Si growth-layer is relatively thin (similar to 10 ML), almost all Ge atoms are segregated at the surface and form Ge-Ge pure dimers and a small amount of Ge-Si mixed dimers. As the growth-layer thickness increases, the portion of pure Ge-Ge dimers decreases, and finall y, the surface is covered with mixed Ge-Si and pure Si-Si dimers at the thi ckness of 64 hit. This result indicates that mixed dimer formation should b e considered as an important factor in the Ce segregation mechanism and Ge incorporation profiles. (C) 1999 Elsevier Science B.V. All rights reserved.