Introduction
Digital Radiography (DR) is being rapidly developed in many areas such as security and medical imaging. In particular, the demand in technologies need improvement in this area either on fabrication or optimization of the screen properties.
The CsI (Tl or Na) scintillation films used in indirect X-ray imaging detectors are usually deposited by using a physical vacuum evaporation technique [2]. Therefore, the films are very expensive and have disadvantages such as cracking and short lifetime [3]. Also, the crystal surface of CsI can be damaged because the Mohs hardness of a commercialized CsI scintillator is 2, which means it is quite soft [4]. The Gd group phosphor screen, combined with
conventional complementary metal-oxide semiconductor (CMOS) or charge-coupled device sensors to capture the X-ray images, has the problem of reduced image resolu- tion due to blurring of the light signal because it has a bulk particle size of more than several microns. If this shortcoming of conventional phosphor screens is to be overcome, studies are necessary to develop an improved large-area phosphor screen with higher resolution, and efficiency \cite{Park_2014}.
Although the Gadox scintillator screen with powdered type and CsI:Tl film with columnar structures by vacuum evaporation are commercially available, the scintillators with higher sensitivity and spatial reso- lution are still required in X-ray imaging detector for dental radi- ography and mammographic application at low X-ray exposure levels (Yorkston, 2007) \cite{Cha_2010}
In this work,