Adsorption of heterobifunctional 4-nitrophenol on the Ge(100)-2×1 surface

We report the adsorption chemistry of a heterobifunctional molecule, 4-nitrophenol, on the Ge(100)-2×1 surface. X-ray photoelectron and infrared spectroscopy experiments and density functional theory calculations were used to determine the adsorption products. The results show that 4-nitrophenol reacts with the Ge surface through either one or both of the OH or NO2 functionalities. It was found that the fraction of dually and singly tethered adsorbates varies according to reaction conditions: namely, singly tethered adsorbates are favored at higher adsorbate coverages and lower adsorption temperatures. These variations are explained by a two-step adsorption mechanism for 4-nitrophenol, in which geometrical limitations of the adsorbates on the surface affect the product distribution. [Display omitted] •Adsorption of 4-nitrophenol at Ge(100)-2×1 was studied.•4-Nitrophenol adsorbs on Ge(100)-2×1 via one or both OH and NO2 functionalities.•More singly bound adsorbates are formed at higher coverages and at lower temperature.•Adjacent free surface sites are required to form dually bound adsorbates.•Formation of dually bound product is exothermic but involves high activation barrier.