van der Waals corrected DFT study of high coverage benzene adsorptions on Si(100) surface and STM simulations

In this work we provide a density functional theory (DFT) study of high coverage metastable benzene adsorption on a Si(100) surface. We examine intra- and inter-dimer interactions, phase ordering and in-dimer-row directional stability. From comparison of transition barriers (nudged elastic band calculations) and energetic stability between the single adsorptions and their high coverage cases we conclude that molecular interactions at high coverage neither influence the relative stability of metastable adsorption nor their reaction barrier. We investigate inter-dimer adsorption of benzene on the C-type defect and discuss its relevance to high coverage. It is found that the high coverage inter-dimer (ID) adsorption has increased stability, similar to C-defect adsorption, while the other mixed cases of ID are less likely to occur. All of the presented calculations are performed in an extended framework with newly implemented Grimme corrections to account for van der Waals interactions (DFT-D), which are benchmarked against standard DFT results. Additionally we present a scanning tunneling microscopy study for the high coverage adsorptions together with its structural analysis, through which we aid high coverage STM identification.