ADSORPTION AND DISSOCIATION OF SI2H6 ON GE(001)2X1

Adsorption and thermally-induced dissociation of disilane (Si2H6) on clean Ge(001)2 x 1 surfaces have been investigated using a combination of Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS), reflection high-energy electron diffraction (RHEED), and scanning tunneling microscopy (STM). With initial Si2H6 exposure at room temperature, the Si surface coverage increased monotonically, the EELS surface dangling bond peak intensities continuously decreased, and the intensity of half-order RHEED diffraction rods decreased. The low-coverage Si2H6 sticking probability at 300 K on Ge(001) was found to be approximately 0.5 while the saturation coverage was approximately 0.5 ML. A new EELS feature, GSH. involving Si-H and Ge-H bond states was observed at Si2H6 exposures phi greater than or similar to 3.4 x 10(13) cm-2. In contrast to Si2H6-saturated Si(001), the saturated Ge(001) surface retains a significant fraction of dimerized bonds. Adsorbed overlayers were highly disordered with the primary species on saturated surfaces being SiH2, GeH, and undissociated SiH3 . Si2H6-saturated Ge(001)2 x 1 substrates were annealed for 1 min at temperatures T(a) between 425 and 825 K. Admolecules were Mobile at T(a) = 545 K giving rise to significant ordering in one-dimensional chains. By T(a) = 605 K, essentially all of the admolecules were captured into coarsened islands. Dangling-bond EELS peaks reappeared by 625 K and the intensities of the half-order RHEED diffraction rods increased. Ge segregation to the surface, which began at T(a) greater than or similar to 625 K, occurred rapidly at T(a) greater-than-or-equal-to 675 K. All H was desorbed by 725 K.