Patterned Nucleation Control in Vacuum Deposition of Organic Molecules

We report a generally applicable method to pattern organic molecules on mesoscopic scales. In our method, organic molecular beam deposition was conducted on substrate surfaces prepatterned with materials to which the organic molecules have larger binding energies in comparison to the substrate. Fully uniform nucleation control at these predefined locations can be achieved by an appropriate selection of the growth parameters including temperature and deposition rate. The physical mechanisms involved are studied by Monte Carlo simulations and stand in good agreement with the experimental findings.

Figure 1

Template-directed nucleation control for organic molecular deposition. (a) Schematic diagram. (b) AFM image of diFc patterned structure.

Figure 2

Relationship between the nucleation control efficiency ($x_{\mathrm{NCE}}$) and the relative periodicity ($p^{*}$) obtained from experiments and MC simulations. When $p^{*}<1$, $x_{\mathrm{NCE}}$ nearly equals unity, indicating the full control of nucleation. When $p^{*}>1$, $x_{\mathrm{NCE}}$ is gradually decreased, indicating partial control of nucleation. The dashed pink line shows the relationship $x_{\mathrm{NCE}}=p^{*-2}$, which should hold for $x_{\mathrm{NCE}}\ll 1$. Insets are AFM images of NPB grown at $133°\mathrm{C}$, showing full nucleation control at $p^{*}=0.8$ (left) and partial nucleation control at $p^{*}=1.3$ (right).

Figure 3

Organic patterns with concentric rings and artificial defects. Scale bars, $10\mu \mathrm{m}$. (a) AFM of an NPB concentric ring pattern with ring width from 600 nm (inside) to $1.7\mu \mathrm{m}$ (outside) and spacing between the rings of 800 nm. Inset: Height profile showing the modulation of the occupation ratio to the organic layer thickness. (b) AFM of artificial defects in an NPB hexagonal dots array with a dot diameter of 300 nm and periodicity of 900 nm. The single-point, double-point, and line vacancies are marked by a circle, an ellipse, and a line, respectively.