On the nature of nanoribbons at the Si/Ag(110) surface: silicene or silicide?

A decade after the publication of the first paper on nanoribbons (NRs) formed at the Si/Ag(110) surface, the nature of these structures is still under debate. Several studies have proposed that these structures are made up of silicene, a single layer of a buckled honeycomb structure of Si atoms. We report on novel NRs models based on new Si coverage measurements and evaluated using density functional theory simulations. Our models are thermodynamically stable, consistent with the experimental Si and Ag coverages, and yield simulated STM images in excellent agreement with the measured data; in contrast, silicene-based models yield unsatisfactory results.