Adsorption and Stability of π-Bonded Ethylene on GaP(110)

Abstract

We have investigated the structural and electronic properties of individual ethylene molecules on the GaP(110) surface by combining low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS) with density functional theory (DFT) calculations. Isolated molecules were adsorbed on in situ cleaved GaP(110) surfaces through ethylene exposures at 300 K and 15 K. DFT calculations suggest two possible stable adsorption geometries for a single ethylene molecule on GaP(110) at low temperature. High-resolution STM images, however, reveal only one adsorption geometry for this system, consistent with the site having the largest computed binding energy. Unlike adsorption of ethylene on other metallic and semiconducting surfaces, ethylene physisorbs to GaP(110) through a weak hybridization of molecular π-states with substrate surface states, leaving the frontier molecular orbitals largely unperturbed. Differential conductivity spectra acquired on single molecules are consistent with self-energy corrected DFT calculations.

Orbital-Resolved Imaging of the Adsorbed State of Pyridine on GaP(110) Identifies Sites Susceptible to Nucleophilic Attack

“…Figure d illustrates the low conductance at negative bias through a d I /d V measurement. Alternatively, the much smaller tunneling currents at negative applied potentials could result from the particular tip–sample distance used . More work beyond the scope of this study would be required to understand the dependence of the d I /d V curve on tip–sample distance.…”

Computational Approaches to Photoelectrode Design through Molecular Functionalization for Enhanced Photoelectrochemical Water Splitting

“…Similar studies were performed to obtain the band‐edge positions of functionalized TiO 2 , Si, MoS 2 , and non‐functionalized transition‐metal dichalcogenides and oxides . Computational and experimental investigations of band‐edge positions are often performed in conjunction, resulting in experimental validation of theoretical values …”

Covalent Functionalization of GaP(110) Surfaces via a Staudinger-Type Reaction with Perfluorophenyl Azide

“…The (110) surface is different from the more commonly studied crystal faces of zinc-blende III–V semiconductors in that it is neither strongly polar nor highly reactive. For example, while ethylene chemisorbs readily onto both Ga- and As-terminated GaAs(100) surfaces at room temperature, it is unstable on the (110) surface of GaP except for very low temperatures . (110) planes do develop a slight polar character upon reconstruction (see Figure a), but the partial polar character of the alternating nucleophilic (anionic lone pairs) and electrophilic (cationic with empty p z orbitals) centers has not yet been exploited in chemical reactions.…”

“…For example, while ethylene chemisorbs readily onto both Ga-and Asterminated GaAs(100) surfaces at room temperature, 14 it is unstable on the (110) surface of GaP except for very low temperatures. 15 (110) planes do develop a slight polar character upon reconstruction (see Figure 1a), but the partial polar character of the alternating nucleophilic (anionic lone pairs) and electrophilic (cationic with empty p z orbitals) centers has not yet been exploited in chemical reactions. A possible chemical route is suggested by the fact that the P surface atoms of GaP(110) exist in environments resembling tertiary phosphines, which undergo the Staudinger reaction 16 with azide molecules to afford phosphine imides with loss of dinitrogen (N 2 ) (see Figure 1b).…”

“…GaP(110) surfaces were obtained by mechanical cleavage under ultrahigh vacuum conditions at room temperature. This procedure yields high-quality flat surfaces with a low density of intrinsic defects 15 (see Figure 1d) that are ideal for chemical functionalization. PFPA molecules were subsequently deposited in situ onto the GaP(110) surfaces at room temperature.…”