Abstract

In-diffusion of Ti into LiNbO₃ has been used to produce optical waveguides which are simple to fabricate and whose properties are easy to control.⁽¹⁾ We have studied the diffusion of Ti into LiNbO₃ by core level X-ray photoelectron spectroscopy in an attempt to determine the valence states present in the in-diffused metal, and whether or not the sites for Ti ions are the same throughout the sample, or whether a distribution of sites throughout the unit cell of LiNbO₃ is indicated. X-ray photo-electron spectroscopy is a useful experimental technique to answer these questions. The characteristic difference in the binding energy of core electrons in a transition-metal ion, for example, depends on the valence state of the ion. The chemical shifts between adjacentvalence states are typically several volts, while the resolution of this technique in determining the spectrum is 0.5V. Thus chemical shifts in the spectrum of the Ti ions indicating the presence of more than one valence can be measured easily. By a similar argument, the characteristic energy separation between titanium levels and oxygen levels can be compared to those in X-ray spectra of TiO₂ and SrTiO₃ where the Ti ions are known to be in the +4 valence state.

© 1976 Optical Society of America