Detection and imaging of the oxygen deficiency in single crystalline YBa$_{\text{2}}$Cu$_{\text{3}}$O$_{\text{7}-δ}$ thin films using a positron beam

Markus Reiner; Thomas Gigl; Rainer Jany; German Hammerl; Christoph Hugenschmidt

doi:10.1063/1.4916032

paper

Detection and imaging of the oxygen deficiency in single crystalline YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ thin films using a positron beam

arXiv:1501.06383 · doi:10.1063/1.4916032

Abstract

Single crystalline YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ (YBCO) thin films were grown by pulsed laser deposition (PLD) in order to probe the oxygen deficiency $δ$ using a mono-energetic positron beam. The sample set covered a large range of $δ$ (0.191< $δ$ <0.791) yielding a variation of the critical temperature $T_{c}$ between 25 and 90\,K. We found a linear correlation between the Doppler broadening of the positron electron annihilation line and $δ$ determined by X-ray diffraction (XRD). Both, the origin of the found correlation and the influence of metallic vacancies, were examined with the aid of ab-initio calculations that allowed us (i) to exclude the presence of Y vacancies and (ii) to ensure that positrons still probe $δ$ despite the potential presence of Ba or Cu vacancies. In addition, by scanning with the positron beam the spatial variation of $δ$ could be analyzed. It was found to fluctuate with a standard deviation of up to $0.079 (5)$ within a single YBCO film.

Detection and imaging of the oxygen deficiency in single crystalline YBa2​Cu3​O7−δ​ thin films using a positron beam

Abstract

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Detection and imaging of the oxygen deficiency in single crystalline YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ thin films using a positron beam