Coverage Effect of Self-Assembled Polar Molecules on the Surface Energetics of Silicon

We show here that optimal control over the work function of Si can be achieved even with half-coverage of molecular dipoles, especially when the pinholes present on the surface are smaller than the depletion region of the semiconductor. Higher coverage than an optimal value contributes minor (or, no) further changes in the work function of the same semiconductor. The results imply that the requirements on the molecules used to control the electrical properties of Si are significantly and nearly completely relaxed. Therefore, the ability of the molecules to form pinhole-free coverage will not be important after a specific coverage.