Scanning Tunneling Microscope Study on C2H2 Adsorption on a Ge(100) Surface
Figs. A. Schematic diagrams of the adsorption configurations proposed for C2H2 on Ge(001): di-$\sigma$-bonded in (a) on-top, (b) end-bridge, and (c) paired end-bridge configurations, and tetra-$\sigma$-bonded in (d) parallel-bridge and (e) rotated-bridge configurations. H atoms in a C2H2 molecule are not shown for simplicity. B. Empty-state STM image of C2H2/Ge(001) (Vs = +0.8 V) [Inset: filled-state (Vs = -2.0 V) image taken simultaneously over the same area]. The characteristic empty-state double maximum of the one-dimer (circle) and quadruple maximum of the two-dimer (square) features indicate C2H2 adsorption in on-top and paired end-bridge configurations, respectively.