Abstract
XPS combined with profiling by Ar2500+ gas cluster ion beam (GCIB) sputtering has been used to obtain new refined data on the polarization and processing-dependent Li/Nb ratio for the surface of a LiNbO3 single crystal. The most suitable GCIB parameters (normal incidence, 10 keV energy) and irradiation dose (less than or equal to 2.7 × 1016 ions/cm2) have been determined and employed to perform high resolution depth profile analysis without cluster ion-induced Li/Nb changes. The Li/Nb profiles obtained for Z cut wafers with positive and negative faces revealed the presence of two distinct regions. The initial 0.3 nm-thick region had a low Li/Nb ratio due to machining and leaching and did not show a dependence on the polarity direction. The next profile region had a constant Li/Nb ratio, which depended on the crystal polarity. The Li/Nb ratio for the Z+ surface of a wafer and a cleaved sample exceeded the values for the Z– surface of a wafer by 1.2 times. This result confirms theoretical predictions of a different stoichiometry for Z+ and Z– terminations and indicates the ability of GCIB to reach the surface condition that is close to the perfect termination.
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