abstract

while polycrystalline lead oxide (poly-pbo) is known to be one of the most promising photoconductors for utilization in x-ray detectors, its major performance parameters such as charge yield and mobility-lifetime product (μτ) are still not well established and require further investigation. combining the conventional x-ray induced photocurrent and pulse height spectroscopy techniques we examine the x-ray photogeneration and recombination processes in poly-pbo. the measurements indicate that the amount of energy required to release a single electron-hole pair w± (inverse of charge yield) strongly depends on the applied electric field and at 10 v/μm reaches ~20 ev/ehp. fitting the measured pulse height spectra with the hecht formula provided μτ for holes and electrons to be 4.1 × 10−8 cm²/v and 10−9 cm²/v, respectively. obtained μτ values combined with recently reported mobility values of charge carriers in pbo suggest a new direction towards an improvement of pbo technology by incorporation of frisch grid or x-ray transistor architectures.

continue reading the article: https://www.nature.com/articles/s41598-017-09168-3

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abstract

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 noncrystalline 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.

continue reading the article: https://link.springer.com/article/10.1007%2fs10853-017-0998-5

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abstract

although polycrystalline lead oxide (pbo) has a long history of application in optoelectronics and imaging, the transport mechanism for electrons in this material has not yet been clarified. using the photo-generated charge extraction by linear increasing voltage (photo-celiv) technique, we provide the temperature- and field-dependences of electron mobility in poly-pbo. it is found that electrons undergo dispersive transport, i.e. their mobility decreases in the course of time. multiple trapping of electrons from the conduction band into the developed band tail is revealed as the dominant transport mechanism. this differs dramatically from the dispersive transport of holes in the same material, dominated by topological factors and not by energy disorder.

continue reading the article: http://iopscience.iop.org/article/10.1088/1361-6463/50/3/035103/meta

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abstract

although polycrystalline lead oxide (pbo) belongs to the most promising photoconductors for optoelectronic and large area detectors applications, the charge transport mechanism in this material still remains unclear. combining the conventional time-of-flight and the photo-generated charge extraction by linear increasing voltage (photo-celiv) techniques, we investigate the transport of holes which are shown to be the faster carriers in poly-pbo. experimentally measured temperature and electric field dependences of the hole mobility suggest a highly dispersive transport. in order to analyze the transport features quantitatively, the theory of the photo-celiv is extended to account for the dispersive nature of charge transport. while in other materials with dispersive transport the amount of dispersion usually depends on temperature, this is not the case in poly-pbo, which evidences that dispersive transport is caused by the spatial inhomogeneity of the material and not by the energy disorder.

continue reading the article: http://www.nature.com/articles/srep33359

the post congratulations to oleksii semeniuk on publishing a paper in scientific reports – nature appeared first on rezniklab and posted by pavlo karasyuk.