Martinez, Robert E.Fontes, E.Golovchenko, JenePatel, J. R.2016-11-181992Martinez, Robert E., E. Fontes, J. A. Golovchenko, and J. R. Patel. 1992. Giant Vibrations of Impurity Atoms on a Crystal Surface. Physical Review Letters 69, no. 7: 1061–1064. doi:10.1103/physrevlett.69.1061.0031-9007http://nrs.harvard.edu/urn-3:HUL.InstRepos:29407030We have measured extremely large anisotropic thermal vibrations of gallium adatoms on a Si(111) surface using x-ray standing waves. At 830 K the rms amplitude normal to the surface is 0.47±0.02 Å while the parallel amplitude is 0.30±0.02 Å. The temperature dependence of these amplitudes deviates significantly from that expected from Debye theory and suggests a significant thermal softening of the surface bonding at elevated temperatures.en-USJournal Article2016-11-1810.1103/PhysRevLett.69.1061