AVS 52nd International Symposium
    Surface Science Monday Sessions
       Session SS2-MoM

Paper SS2-MoM9
Terminal Oxygen Structures on WO@sub 3@(100) Thin Films

Monday, October 31, 2005, 11:00 am, Room 203

Session: Oxide Surface Structure and Characterization
Presenter: E.I. Altman, Yale University
Authors: M. Li, Yale University
A. Posadas, Yale University
C. Ahn, Yale University
E.I. Altman, Yale University
Correspondent: Click to Email
Scanning tunneling microscopy (STM) was used to characterize the surface reconstructions on epitaxial WO@sub 3@(100) thin films on LaAlO@sub 3@(100) in a reducing environment. As the films were annealed between 600-770 K, a myriad of surface structures related to terminal oxygen were observed. Upon initial reduction the surface was covered with small c(2x2), p(2x2), c(4x2), and poorly ordered terminal oxygen terraces all coexisting with (1x1) islands. Further reduction caused large flat terraces of poorly ordered terminal oxygen to coexist with strand terminated p(nx2) terraces with n = 3-5. Continued reduction led to a zigzag arrangement on top of the p(nx2) surface, half-height p(2x2) and c(4x2) islands, and a local (15x2) structure. The latter three structures could only be explained by crystallographic shearing of the surface plane. In contrast to higher annealing temperatures, the exclusively p(nx2) terminated surface characterized by alternating strands and troughs was not observed, suggesting that at lower temperatures crystallographic shear competes with the bulk migration responsible for trough formation as the dominant surface reduction mechanism.