“…27,35 Three possible adsorption geometries of C 2 H 4 on group IV (100) surfaces are shown in Figure 1 and have been considered here: (a) on-top (OT), (b) single end-bridge (SEB), and (c) paired end-bridge (PEB) configurations. The configuration of a C 2 H 4 molecule bonded on top of each surface dimer (OT) has been the most popular structure model on both Si(100) 11,21,[36][37][38] and Ge(100). 27,28,35 However, a recent first-principles study of C 2 H 4 on Ge(100) has considered other adsorption geometries, including an end-bridge configuration where C 2 H 4 molecules bridge two neighboring dimers within the same dimer row as shown in Figure 1, parts b and c. 35 Using temperature programmed desorption (TPD) spectroscopy and multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy, Bent and co-workers reported that ethylene desorbs from Ge(100) with two types of desorption features and suggested that although C 2 H 4 chemisorbs on Ge-(100) in only one adsorption configuration (OT) at room temperature, a second adsorption configuration that could not be identified arises during the heating process of thermal desorption experiments.…”