Experimental test of the quantum-mechanical image-force theory

Both photon-assisted-tunneling and internal photoemission measurements have been made on the same metal-oxide-semiconductor samples. The effective barrier heights between the metal (Al or Au) and the oxide (SiO₂) extracted from the internal photoemission measurements are found to be larger by {~}0.3 eV than the effective barrier heights extracted from the photon-assisted-tunneling measurements. Only the quantum-mechanical image-force theory is capable of explaining this result.