RBS-channeling, ERDA and XRD study of lithium tantalate modified by annealed proton exchange (APE)

Lithium tantalate (LT) single crystals are very promising substrates for constructing highly sophisticated photonics devices. The used procedure for fabricating optical waveguides in them was annealed proton exchange (APE). Here we have used Rutherford backscattering spectrometry (RBS) – channeling analysis, X-ray diffraction (XRD) and elastic recoil detection analysis (ERDA) to study changes in the surface of the LT wafers caused by the APE treatment and to determine the concentration depth profiles of hydrogen atoms. The measurements were taken for both virgin (untreated) and APE:LT samples fabricated using various experimental conditions. We have found that the incorporation of hydrogen during the first step, i.e. the PE procedure (proton exchange), leads to modifications of the structure of the LT single crystal, which gradually relaxed towards the structure of the original LT during the post-proton-exchange annealing (A). This study also revealed a substantial dependence of sample behaviour on the crystallographic orientation of the pertinent substrate wafers (commonly used X-(〈1 1 −2 0〉) and Z-(〈0 0 0 1〉) cuts).