First principles calculations of the adsorption of acetylene on the Si(001) surface at low and full coverage

Bond Insertion at Distorted Si(001) Subsurface Atoms

“…The observation is also in stark contrast to the adsorption of alkenes like ethylene, which undergo a cycloaddition with one or two surface dimers mediated by a coordination of the molecular π system to a Sidown atom (π complex) [21][22][23][24][25][26][27]. For the adsorption of acetylene, cycloadducts are the most stable adsorption modes as well, as confirmed by theoretical calculations and experimental measurements at room temperature [20,21,[28][29][30][31][32][33][34][35][36]. While there is experimental evidence for the presence of an intermediate state (called precursor in surface science) [37], there is no consensus on the nature of this state.…”

“…While there is experimental evidence for the presence of an intermediate state (called precursor in surface science) [37], there is no consensus on the nature of this state. Statements that have been made include a mobile precursor [37], a π complex [28,30], no stable precursor at all [21,35], and the bond insertion structure [20].…”

Electronic and optical properties of acetylene and ethylene on Si(001)

“…ethylene, this instead happens only for the on-top geometry, while a barrier of ∼0.12 eV must be overcome in order to reach a bridge configuration. However more recent calculations [26], performed at lower coverages, show that also in the case of acetylene, a barrier of 0.19 eV has to be overcome in order to reach the bridge configuration from an intermediate state. Thus, the origin of the different behavior of the two molecules must still be clarified.…”

Modeling of 1,4-cyclohexadiene adsorption thermodynamics on Si(001)-2 × 1 surface

“…Later, these π-precursors were observed experimentally [14]. The available experimental data [9][10][11][12][15][16][17][18][19] are ambiguous and, therefore, most of the theoretical works are focused on the quantum-chemical calculations of binding energies for the different adsorption configurations [5,[19][20][21][22][23][24].…”

“…However, the question of what thermodynamics or kinetics determine the first stage of organic film growth and, consequently, the adsorption configuration of molecules on the surface is still open [9,[20][21][22][23][24][25][26][27].…”