Ion-assisted deposition of amorphous PbO layers
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Lead oxide (PbO) is one of the most promising materials for application in direct conversion medical imaging X-ray detectors. Despite its high potential, conventional polycrystalline PbO layers deposited with the basic thermal evaporation method are not yet mature for practical use in X-ray imaging; indeed, they are highly porous, unstable at ambient conditions, and substoichiometric. In order to combat the above issues with PbO, we advance the basic evaporation process with simultaneous energetic ion bombardment of the growing film. We show that tuning the ion-assisted thermal deposition not only solves the structural problems of poly-PbO, but also enables the growth of a new non-crystalline polymorphic form of the material—amorphous PbO (a-PbO). In contrast to poly-PbO, novel a-PbO layers grown by ion-assisted thermal deposition are stable at ambient conditions. Structural and morphological analysis confirms that a-PbO is stoichiometric and free of detectable voids, which suggests higher bulk X-ray stopping power than porous poly-PbO.
KeywordsPbO2 Grown Layer Pb3O4 Hydrocerussite Secondary Neutral Mass Spectrometry
The authors are thankful to Dr. Matthias Simon, Philips Research Labs, and Prof. Kai Wang, Joint Institute of Engineering at Carnegie Mellon University, for help in optimizing the PbO growth process. The authors gratefully acknowledge the financial support from the National Science and Engineering Research Council (NSERC), Canadian Institute for Health Research (CIHR) and Ontario Research Fund—Research Excellence (ORF-RE) program. Also, this publication is supported by the GINOP-2.3.2-15-2016-00041 project. The project is co-financed by the European Union and the European Regional Development Fund. Support by the TAMOP 4.2.2.A-11/1/KONV-2012-0036 project, which is co-financed by the European Union and European Social Fund, is also acknowledged.
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Conflict of interest
The authors declare that they have no conflict of interest.
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