Polymer adhesion: First-principles calculations of the adsorption of organic molecules onto Si surfaces

The structures and energetics of organic molecules adsorbed onto clean and H-passivated $\mathrm{Si}\left(001\right)\text{−}(2\times 1)$ surfaces have been calculated using density functional theory. For benzene adsorbed on the clean Si surface the tight-bridge structure was found to be stable and the butterfly structure metastable. Both carbonic acid, ${\mathrm{H}}_2\mathrm{C}{\mathrm{O}}_3$, and propane, ${\mathrm{C}}_3{\mathrm{H}}_8$, dissociate on contact with the surface. Passivation of the Si surface with H atoms has a dramatic effect on the surface properties. The passivated surface is very inert and the binding energy of all the molecules is very weak.

Figure 1

(Color online) The monomer bisphenol-$A$-polycarbonate (BPA-PC) and its analogous molecules, benzene $\left({\mathrm{C}}_6{\mathrm{H}}_6\right)$, carbonic acid $\left({\mathrm{H}}_2\mathrm{C}{\mathrm{O}}_3\right)$, benzene and propane $\left({\mathrm{C}}_3{\mathrm{H}}_8\right)$.

Figure 2

(Color online) The clean $\mathrm{Si}\left(001\right)\text{−}(2\times 1)$ dimer reconstruction (left) and H-passivated $\mathrm{Si}\left(001\right):\mathrm{H}\text{−}(2\times 1)$ surface (right) viewed along the [110] direction.

Figure 3

(Color online) “Butterfly” structure of ${\mathrm{C}}_6{\mathrm{H}}_6$ on $\mathrm{Si}\left(001\right)\text{−}(2\times 1)$ viewed along $\left[\overline{1}10\right]$ and [110] (dimer rows), respectively.

Figure 4

(Color online) “Tight-bridge” structure of ${\mathrm{C}}_6{\mathrm{H}}_6$ on $\mathrm{Si}\left(001\right)\text{−}(2\times 1)$ viewed along $\left[\overline{1}10\right]$ and [110], respectively.

Figure 5

(Color online) The ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{C}{\mathrm{O}}_3{\mathrm{C}}_6{\mathrm{H}}_5$ molecule represents part of the BPA-PC monomer containing the carbonate group.

Figure 6

(Color online) The lowest energy adsorption structure of ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{C}{\mathrm{O}}_3{\mathrm{C}}_6{\mathrm{H}}_5$ adsorbed on Si. Both phenol rings have the tight-bridge structure. Left: viewed along $\left[\overline{1}10\right]$. Right: viewed along [110] dimer rows.

Figure 7

The isolated ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{C}}_3{\mathrm{H}}_6{\mathrm{C}}_6{\mathrm{H}}_5$ molecule which is a segment of BPA-PC containing the propane group.

Figure 8

(Color online) ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{C}}_3{\mathrm{H}}_6{\mathrm{C}}_6{\mathrm{H}}_5$ on $\mathrm{Si}\left(001\right)\text{−}(2\times 1)$ viewed along $\left[\overline{1}10\right]$ and [110], respectively.

Figure 9

(Color online) Adsorption sites on $\mathrm{Si}\left(001\right):\mathrm{H}\text{−}(2\times 1)$.

Figure 10

(Color online) Side and top views of benzene adsorbed on site $C$ of the $\mathrm{Si}\left(001\right):\mathrm{H}\text{−}(2\times 1)$ surface and with orientation (II).

Figure 11

Barriers for adsorption of ${\mathrm{C}}_6{\mathrm{H}}_6$ on site C(II) of $\mathrm{Si}\left(001\right)\text{−}(2\times 1)$ and $\mathrm{Si}\left(001\right):\mathrm{H}\text{−}(2\times 1)$.

Figure 12

(Color online) Carbonic acid molecule adsorbed on the H-passivated Si surface with configuration B(III). Left: viewed along $\left[\overline{1}10\right]$. Right: viewed along [110] dimer rows.

Figure 13

(Color online) Propane molecule adsorbed on the H-passivated Si surface with configuration (I). Left: viewed along $\left[\overline{1}10\right]$. Right: viewed along [110] dimer rows.