AUGER LINE SHAPE OF M_(2,3) VV MEASURED WITH POSITRON ANNIHILATION INDUCED AUGER ELECTRON SPECTROSCOPY

摘要

Positron annihilation induced Auger spectroscopy (PAES) utilizes matter-antimatter annihilation to create the core-holes necessary for Auger transitions. Therefore it is possible to eliminate background due to collisionally induced secondary electrons by setting the incident positron beam energy below that of the Auger electrons. Previous measurements indicate that the background-free Auger line shapes obtained using PAES differ significantly from the ones obtained using electron excitation and conventional background subtraction techniques. However quantitative PAES line shape analysis has been hampered due to the lack of energy resolution of the original PAES system. A new PAES spectrometer has been developed in our lab with an energy resolution, △E/E = 2%, an order of magnitude better than previous PAES spectrometers. The high-resolution PAES system has been used to measure the Auger M_(2,3)VVline shape from a clean polycrystalline Cu surface. The atomic-like Auger M_2VV and M_3VV features are clearly resolved and separated by 2.4 eV, a value which is consistent with the published electron induced Auger measurements. The spectral intensity at the low energy tail of M_(2,3)VV in our PAES measurement suggests a non-trivial contribution from the "band-like" components of the Auger transition and intrinsic losses, and also suggests that previous modeling of the secondary electron background leads to an underestimate of the low energy tail of the Auger line shape.