Single Phosphorus Atoms in Si(001): Doping-Induced Charge Transfer into Isolated Si Dangling Bonds

Abstract

Using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, we show that the structure of isolated Si dangling bonds on the Si(001) surface is critically influenced by the doping of the silicon substrate. Substitutional phosphorus atoms in the surface form Si−P heterodimers that contain a single, isolated Si dangling bonda common feature of many adsorbate species and surface defects on Si(001). In our STM measurements, the Si−P heterodimer is observed to adopt a different appearance on n- and p-type substrates. DFT calculations show that this difference arises due to the creation and occupation of a localized defect state associated with the Si dangling bond. Depending on the substrate doping, charge is transferred into the Si dangling bond leading to a relaxation of the geometric and electronic structure.