ELFT HÍRADÓ

[Horváth Zsolt Endre <horvath.zsolt.endre AT energia.mta.hu>]

Kedves Kollégák!


Február 19-én szerdán, a szokásos időben,  11 órakor az MFA 
tanácstermében (KFKI 26. épület 1. emelet) kerül sor


           Dr. Alla Reznik (Lakehead University, Thunder Bay, Kanada):



     Amorphous lead oxide (a-PbO) for application in digital direct
     conversion X-ray medical imaging detectors



     **

c. előadására.


Abstract:

Semiconductor-based direct-conversion X-ray detectors have been actively 
sought for a wide range of x-ray applications in the fields of domestic 
security and medical imaging [1].  Lead Oxide (PbO) is one of the most 
promising high Z (atomic number) candidates for this purpose due to high 
X-ray stopping power, high theoretical X-ray-to-charge conversion gain 
and proven technological compatibility with a-Si electronics required 
for a large detector area coating. Polycrystalline modification of lead 
oxide (poly-PbO) has a long and successful history of applications in 
optoelectronics where it was employed as a phototarget in Plumbicons – 
the most extensively used pick-up tubes for broadcasting. The success of 
Plumbicons triggered great interest in utilizing PbO layers for X-ray 
medical imaging detectors. Unfortunately, poly-PbO photoconductive 
layers were reported to be challenging for applications in real-time 
X-ray medical imaging due to the presence of a residual signal after 
exposure termination, called signal lag. Signal lag leads to inadequate 
temporal characteristics and therefore it is a bottle neck of 
performance for many non-crystalline materials, considered for dynamic 
radiation sensing. Here we analyze causes of signal lag in poly-PbO 
layers and show that a technological step to replace nonhomogeneous 
disorder in polycrystalline PbO with homogeneous amorphous PbO structure 
suppresses signal lag and improves time response to X-ray irradiation. 
Our study suggests a way to make detector-grade PbO layers free of lag. 
The proposed advances of the deposition process are low cost, easy to 
implement and with certain customization might potentially be applied to 
other materials, thus paving the way to their wide-range commercial use.

[1]    S.O. Kasap and J.A. Rowlands, Physics Today, 50, 24 (1997)



A szemináriumon minden érdeklődőt szívesen látunk!

Horváth Zsolt Endre Szeminárium koordinátor

--
Dr. Zsolt E. HORVÁTH
Institute for Technical Physics and Materials Science,
Centre for Energy Research
Hungarian Academy of Sciences
(MTA EK MFA)
Konkoly Thege Rd. 29-33, 1121 Budapest,
Mail: P.O.Box 49, H-1525 Budapest, Hungary
Phone: +36-1-392-2680, Fax: +36-1-392-2226
e-mail:horvath.zsolt.endre AT energia.mta.hu