Photoemission from Al–Al2O3 Films in the Vacuum Ultraviolet Region

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Abstract
Measurements of quantum yield of Al–Al2O3 films were made at photon energies between 7 and 22 eV. The photoelectric threshold for intrinsic photoemission from amorphous Al2O3 appeared to be about 8 eV. Approximately 1 eV was estimated for the electron affinity of Al2O3. The yield of anodic oxide film on aluminum at 10.2 eV decreased with increasing oxide thickness while the yield at 21.2 eV increased. The decrease in yield at 10.2 eV was a tributed to photoelectrons originating from the aluminum film beneath the oxide layer. Attempts were made to study the escape probability function for electrons moving through the oxide into the vacuum. An attenuation length of about 130 Å for the photoelectrons in the oxide was obtained by using the exponential‐function approximation. The maximum initial energy of the electrons was estimated to be 7.8 eV above the vacuum level. The electron mean free path for electron‐phonon collisions in the oxide was estimated to be approximately 16 Å. Key words: Photoelectric effect, vacuum ultraviolet, photoelectric threshold, Al2O3 films, thin films, electron attenuation length, electron mean free path.