Single crystal strontium titanate surface and bulk modifications due to vacuum annealing


Single crystal strontium titanate surface and bulk modifications due to vacuum annealing

Hanzig, J.; Abendroth, B.; Hanzig, F.; Stöcker, H.; Strohmeyer, R.; Meyer, D. C.; Lindner, S.; Grobosch, M.; Knupfer, M.; Himcinschi, C.; Mühle, U.; Munnik, F.

Vacuum annealing is a widely used method to increase the electric conductivity of SrTiO3 single crystals. The induced oxygen vacancies act as intrinsic donors and lead to n-type conductivity. Apart from the changed electric properties, however, also structural modifications arise from this treatment. The present paper provides a survey of the real structure of commercially available SrTiO3 single crystals and the changes to the real structure induced by reducing vacuum heat-treatment. Used characterization methods include atomic force microscopy, transmission electron microscopy, X-ray diffraction, spectroscopic ellipsometry, infrared and photoluminescence spectroscopy. Beside the expected variation of bulk properties, especially surface modifications have been detected. The intrinsic number of near-surface dislocations in the samples was reduced by vacuum annealing. Furthermore, X-ray photoelectron spectroscopy proves the existence of a contamination layer on the surface which disappears upon increased annealing time and affects the workfunction. Also, the interaction between adsorbates and surface point defects as well as laser
annealing due to local oxygen absorption are discussed.

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Publ.-Id: 15407