NH3 on Si(001): Self-organized patterns of adsorbates investigated by a combination of scanning tunneling microscopy experiments and density functional theory calculations

The adsorption and dissociation of NH3 on Si(001) has been investigated by a combination of scanning tunneling microscopy experiments and density functional theory calculations. We have identified the NH2 adsorbed group and used this to analyze the arrangement of adsorbed molecular fragments on this surface. We find that there is a statistically significant ordering to these fragments, which changes with adsorption temperature. We propose that a hydrogen-bonding interaction between adsorbed fragments and impinging molecules is responsible for the observed ordering at room temperature, which has general implications for the adsorption of organic molecules on this surface. © 2005 The American Physical Society.