Many metals emit electrons when exposed to UV radiation from excimer lasers (photon energies 4 eV to 8 eV). Deformation can significantly affect the intensity of these emissions. In the case of reactive metals, these emissions are also altered by the presence of surface oxides. We have characterized the effect of thermal oxides on laser-induced photoelectron emission from commercially pure, polycrystalline aluminum with a view toward using these emissions as a probe of deformation processes. The thickness of oxides produced by a range of annealing treatments in air was determined by x-ray photoelectron spectroscopy. Time-of-flight measurements on photoelectrons from these surfaces under 248 nm irradiation (5 eV photons) show two peaks: a fast peak which we attributed to electrons from metallic aluminum, and a slower peak, which may be due to electrons from interface states. Both peaks are attenuated by sufficiently thick oxides. We show that the sensitivity of the photoelectron signals to deformation-induced changes can be optimized by an appropriate choice of oxide thickness. With an appropriate oxide, the total photoelectron intensity is a sensitive probe of deformation-related processes during tensile testing.
Citation: Journal of Applied Physics
Pub Type: Journals
Aluminum, oxide, deformation structure, x-ray photoelectron spectroscopy, photoelectron emission