Search

The adsorption of PBr3on the Si(100)-2 × 1 surface was studied by scanning tunneling microscopy (STM) and density functional theory (DFT). The PBr3molecule completely dissociates on the Si(100) surface at room temperature into P and Br atoms. In most cases, the dissociated molecule was observed in STM on three neighboring Si dimers. DFT calculations confirm that the PBr3molecule can completely dissociate at room temperature. After annealing the sample to 400 °C, phosphorus is incorporated into silicon, as evidenced by the Si atoms ejected to the surface. These findings are useful for the insertion of individual phosphorus atoms into silicon by PBr3adsorption through a halogen mask.

The structures formed by propylene adsorption on Ni(111) at room temperature are determined by a combination of scanning tunneling microscopy and density functional theory. As a result of the interaction with the Ni(111) surface, propylene molecules are dehydrogenated and coupled into linear hydrocarbon chains. The length of the chains varies from 8 to 60 Å, with the most frequently observed length of 18 Å. At saturated coverage, some chains are closed in rings with a diameter of 6 Å. A C12H12model is proposed for most often observed chains. We demonstrate the possibility of combining initial propylene molecules into chains after dehydrogenation of the CH3fragment.

Scanning tunneling microscopy, low-energy electron diffraction, Auger electron spectroscopy, and density functional theory calculations have been used to investigate I2adsorption on the Ni(110) surface. Dissociative adsorption takes place rapidly to form a c(2 × 2) layer at an iodine coverage of 0.5 ML. DFT calculations show that hollow sites are energetically preferable for iodine adsorption on the Ni(110) surface. Increase of iodine coverage above 0.5 ML leads to the commensurate–incommensurate phase transition via nucleation of loops of domain walls and to their subsequent ordering into the striped superstructure. At saturation, a striped domain-wall phase degenerates into the uniaxially compressed quasi-hexagonal phase. Further iodine dosing leads to the nucleation and growth of 2D nickel iodide islands.

The homoepitaxial growth of Si on Si(100) covered by a resist mask is a necessary technological step for the fabrication of donor-based quantum devices with scanning tunneling microscope lithography. In the present work, the chlorine monolayer is selected as the resist. Using density functional theory, we investigated the adsorption of a single silicon atom on Si(100)-2 × 1-Cl as the starting process of Si epitaxy. The incorporation of a silicon atom under a Cl monolayer proved to be the most energetically favorable process. Our results show that chlorine segregates on the surface during Si deposition and does not incorporate into homoepitaxial layers. In addition, we found that SiCl2*, SiCl3*, and SiCl4*clusters can be formed above a Si(100)-2 × 1-Cl surface while Si is adsorbed. SiCl2*clusters are bound weakly to the substrate, and their desorption leaves the silicon surface free of chlorine. To check whether the Si epitaxy is possible on the chlorine resist, we compare our results with the well-studied case of a hydrogen resist. We find the two processes to be similar; moreover, epitaxy on chlorine resist appears to have an advantage.

Coadsorption of chlorine and oxygen on the Ag(111) surface has been studied with low-temperature scanning tunneling microscopy in combination with density functional theory calculations. Room-temperature adsorption of chlorine onto the Ag(111)-p(4 × 4)–O surface leads to the appearance of new bright objects located between protrusions of the 4 × 4 reconstruction. As chlorine adsorbs, objects form “rosettes” around corner holes. This configuration coincides with the configuration of the chlorine atoms in the Ag(111)-(3 × 3)–Cl reconstruction structure. We conclude that the adsorption of chlorine on the Ag(111)-p(4 × 4)–O surface occurs dissociatively, with chlorine atoms displacing oxygen atoms from the 4-fold positions. Adsorption of chlorine at 77 K results in the formation of the mixed Cl–O species on the Ag6triangles of the p(4 × 4) reconstruction. Both scenarios of chlorine adsorption are unexpected and cannot be explained within a commonly accepted Ag6model of the p(4 × 4) reconstruction.

This paper presents a density functional theory study for phosphine adsorption on a Si(001)-2 × 1 surface covered by a chlorine monolayer, including adsorption on local defects, i.e., mono- and bivacancies in the adsorbate layer (Cl, Cl2), and combined vacancies with removed silicon atoms (SiCl, SiCl2). Activation barriers were found for the adsorbing PH3to dissociate into PH2+ H and PH + H2fragments; it was also established that phosphine dissociation on combined vacancies is possible at room temperature. If there is a silicon vacancy on the surface, phosphorus settles in the Si(001) lattice as PH (if the vacancy is SiCl) or as PH2(if the vacancy is SiCl2). This paper suggests a method to plant a separate phosphorus atom into the silicon surface layer with atomic precision, using phosphine adsorption on defects specially created on a Si(001)-2 × 1–Cl surface with a scanning tunneling microscope tip.

First-principle density-functional calculations have been applied to study the interaction of molecular chlorine with the (111) plane of copper. Using transition-state search method, we considered the elementary processes (Cl2dissociation, adsorption, diffusion, association, and desorption) on the chlorinated Cu(111) surface. A systematic study of possible desorption pathways has been carried out for different species (Cl, Cl2, CuCl, CuCl2, and Cu) at various chlorine coverage. As a result, we concluded that chlorine monolayer irrespective of the coverage desorbs in the form of CuCl molecules from step edges.

Adsorption of molecular chlorine on Au(111) has been studied with a low-temperature (5 K) scanning tunneling microscope in combination with density functional theory calculations. The formation of AuCl2quasi-molecules was detected at chlorine coverage exceeding 0.33 ML. The self-organization of the AuCl2species into the ordered “honeycomb” structure was clearly demonstrated for coverages close to saturation.