Chemical trends in metal-semiconductor barrier heights

Experimental data on metal-semiconductor interfaces are reexamined. It is found that the previously reported abrupt transition between covalent and ionic semiconductors is not that clearly defined and the outcome is diffused by data scattering. Furthermore, the data indicate no saturation of the interface parameter S for $S=1$. Considering the definition of S, it follows that the true Schottky limit should occur for some number S≈2.0-3.0 rather than for exactly $S=1$ as previously claimed.