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. © 1982 The American Physical Society.