Mass and energy dependence of depth resolution in secondary-ion mass spectrometry experiments with iodine, oxygen, and cesium beams on AlGaAs/GaAs multilayer structures

The use of an I+2 and I+ primary ion beam in secondary-ion mass spectrometry measurements was studied to investigate its depth profiling properties. A comparison with the results of a Cs+, O+2, and O+ primary beam was made. Experiments were performed with low impact energy (down to 1.7 keV) and glancing angle of incidence on molecular beam epitaxy AlGaAs-GaAs multilayer structures. The best obtainable decay length of the Al+ signal with an iodine primary beam is 1.1 nm. At low impact energies, no mass dependence on the depth resolution is observed. In these conditions, a useful yield for Al+ of approximately 5×10−5 was obtained with the Cs+ beam and 10−2 with the iodine and oxygen beams.