Effects of Subsurface Boron and Phosphorus on Surface Reactivity of Si(001):  Water and Ammonia Adsorption

Abstract

Using density functional slab calculations with planewave basis set and pseudopotentials, we have examined the effect of subsurface boron and phosphorus on the surface chemical properties of Si(001). We compare the adsorption behaviors of water and ammonia between B-or P-modified and clean Si(001) surfaces. On the B-modified surface, the charge polarization of two B-connected dimers is altered significantly. Our calculation shows that approximately one electron is transferred from the local surface to the subsurface boron, thereby leading both buckled-up and -down atoms of B-connected dimers to be electron-poor (electrophilic). On the other hand, subsurface P brings about no significant change in surface electronic structure. Only about onetenth of an electron is transferred from the subsurface P to the local surface. As a result, relative to the clean surface, the adsorption properties of water and ammonia change noticeably on the B-modified surface while varying insignificantly on the P-modified surface.

Toward Atomic-Scale Patterned Atomic Layer Deposition: Reactions of Al2O3 Precursors on a Si(001) Surface with Mixed Functionalizations

“…However, regarding H 2 O adsorption and dissociation, subsurface incorporated B atoms are likely to insignificantly affect adsorption and dissociation kinetic barriers, and only small changes in the adsorption energy (of 0.15 eV), as a consequence of the change in the surface polarization, will be noticeable. 67 The situation is remarkably different in the presence of surface defects like Si dangling bonds. Indeed, We also want to investigate the effect of B-subsurface doping on the second half of the ALD reaction, i.e., the adsorption of the TMA molecule.…”

“…Then, it is possible to envisage atomic-scale manipulation of surface chemical properties by incorporating dopant atoms into the surface or subsurface. Boron is the most widely used p -type impurity in Si, and it is a well-known property that B atoms remain in subsurface lattice sites, rather than staying at the surface . A B atom at the subsurface alters the local atomic structure, because of its small atomic radius, and also modifies the charge polarization of B-connected Si dimers.…”

“…A B atom at the subsurface alters the local atomic structure, because of its small atomic radius, and also modifies the charge polarization of B-connected Si dimers. However, regarding H 2 O adsorption and dissociation, subsurface incorporated B atoms are likely to insignificantly affect adsorption and dissociation kinetic barriers, and only small changes in the adsorption energy (of 0.15 eV), as a consequence of the change in the surface polarization, will be noticeable . The situation is remarkably different in the presence of surface defects like Si dangling bonds.…”

Real-Time X-ray Photoemission Spectroscopy Study of Si(001)-2×1 Exposed to Water Vapor: Adsorption Kinetics, Fermi Level Positioning, and Electron Affinity Variations

“…This negative result is surprising. Indeed, DFT calculations 32 show that boron doping increases the molecular adsorption energy with respect to phosphorus doping (0.87 eV versus 0.80 eV). This in turn should impact both desorption and dissociation rate constants of the molecular precursor, which is not the case.…”

“…It also must be recognized that kinetics and electronic structure are interrelated issues. A recent theoretical work shows indeed that doping affects the adsorption energy of molecular waters, 32 which in turn may have an impact on the desorption and the dissociation rate constants of a predissociative molecular precursor. Therefore, the influence of doping level on the kinetics was examined in a wide range of doping type and levels (from highly doped n to highly doped p).…”