AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM-ThP

Paper EM-ThP2
First Principles Calculations of Ge (100) Covered by Up to One Monolayer of Pb

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Electronic Materials and Processing Poster Session
Presenter: N. Takeuchi, Universidad Nacional Autonoma de Mexico
Correspondent: Click to Email
We have performed first principles total energy calculations to determine the atomic structure of the Ge(100) surface covered with different amounts of Pb. For low coverages, Pb starts growing parallel to the underlying Ge dimers (without breaking them), and it forms asymmetric dimers. This situation continues up to half a monolayer. At this coverage, several structures are possible: (2x2), p(4x2), etc. They are also formed by asymmetric Pb dimers on top of the Ge(100) surface. They differ from each other by the orientation of the buckled dimers. When the coverage is larger, the Ge dimer bonds start to break. >From this coverage,and up to one monolayer, the stable surface shows a c(4x8) reconstruction, similar to the one found in Sn on Si(100) and Pb on Si(100).It consists of rows of Pb ad-dimers, with one missing row out of every four, yielding a coverage of 0.75 of a monolayer.The dimers are also asymetric. Calculated local density of states are in excellent agreement with scanning tunneling microscope images. Surface formation energies show that this configuration is more stable than the full monolayer (2x1) structure.