0018-9499 (c) 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TNS.2016.2567444, IEEE Transactions on Nuclear Science > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract—CsI(Tl) scintillator films with columnar structure are widely applied as the conversion screens for the indirect X-ray imaging. In this work, CsI(Tl) films with different micron thickness were fabricated on glass substrates by the thermal deposition method under the same deposition conditions. The influence of film thickness on the microstructure and crystalline property of the films was studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photoluminescent spectra of the films were measured, which appeared by the bimodal distribution peaking at 550 nm and 740 nm respectively. The radioluminescence and imaging performances were observed by the micron thick films coupled with CCD camera system under X-ray exposure conditions. Index Terms—CsI:Tl film, micron thickness, scintillation properties, X-ray imaging. I. INTRODUCTION owadays advanced digital X-ray imaging systems tend to the combinations of a series of scintillation screens coupled to the state-of-the-art charge-coupled device (CCD) or amorphous silicon detector arrays (a-Si:H) [1]-[3]. Because of high scintillation efficiency for X-ray radiation, high spatial resolution and good match with spectral sensitivity of Si-based readout arrays, CsI(Tl) scintillator films are widely applied in X-ray imaging as the promising convertors [4]-[9]. CsI(Tl) scintillation screens with large area and different thicknesses for using in X-ray imaging, such as non-destructive evaluation, high-speed X-ray imaging camera, macromolecular crystallography and digital mammography, have been commercially available [10]-[12]. In this work, the crystallization and luminescence properties of micron thickness CsI(Tl) scintillator films were studied. The CsI(Tl) films were prepared on glass substrates by thermal This work was supported by 973 Program of China (2012CB315701), the National Natural Science foundation of China (Grant No. 61177035), Sichuan Provincial International Cooperation Project (2013HH0002) and Sichuan Provincial Science and Technology Support Project (12ZC0245). The authors would also like to thank CCD Research Center of China Electronics. Lina Guo, Shuang Liu, Dejun Chen, Shangjian Zhang and Yong Liu are with School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054, China (Corresponding author, e-mail: shuangliu@uestc.edu.cn). Zhiyong Zhong is with State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China （e-mail: zzy@uestc.edu.cn）. Charles M. Falco is with University of Arizona, College of Optical Sciences, Arizona, USA 85721 （e-mail: falco@u.arizona.edu）. evaporation method. The microcolumnar morphology was observed by scanning electron microscopy (SEM). The crystallographic performance of the films with different micron thickness was changed according to their X-ray diffraction (XRD) patterns. The radioluminescence (RL) was measured and the influence of film thickness on the luminescent performance was discussed. The X-ray images of a key were obtained through the CsI(Tl) films coupled with CCD camera system and the contrast values of these images are calculated. With higher film thickness, the characteristic of single crystal and the preferred orientations were maintained, though there was a distinct change of the diffraction peaks from (200) to (310) orientation. The photoluminescent spectra of the films with micron thickness were attractive, which appeared by the bimodal distribution peaking at 550 nm and 740 nm respectively. The X-ray images were better than expected, and would have a beneficial effect for the study of thicker films. II. EXPERIMENTAL CsI(Tl) scintillator films onto the glass substrates above 10cm distance from a molybdenum boat with the mixture of CsI and 1.0mol% Tl powder were fabricated by thermal evaporation. The CsI(Tl) films with 1 μm, 3 μm and 6 μm thickness were deposited at the specific evaporation conditions. During CsI(Tl) vapor deposition process, the vacuum chamber pressure was maintained at 10 -5 Pa and the temperature of the substrates was at room temperature. The cooling water pipe was closely arranged above and around the turntable fixing the substrates to maintain the substrate temperature at 27 ℃, which was monitored by the temperature control system. And the source temperature was kept around at 1000 K in order to maintain uniform designated evaporation rate. A QUANTA FEG 450 scanning electron microscope was used to observe the film morphology. The film crystallographic characteristic was examined using a high-resolution X-ray diffraction (Philips PW1710) in CuKα radiation with an analysis range 2θ of 20-90° . The photoluminescent spectra of films were examined by using an FLSP 920 Edinburgh Instruments Ltd. Spectrometer with Xe lamp excitation and F900 analyzer. The X-ray radiographic images of the part of a key sheathed in the black plastic shell were obtained through the CsI(Tl) scintillator films coupled with the CCD imaging system. The X-ray source was at 90 kVp acceleration voltage and 30 mA beam current, which would ensure the image quality. The image intensities gathered from the CCD imaging system Fabrication and Performance of Micron Thick CsI(Tl) Films for X-ray Imaging Application Lina Guo, Shuang Liu, Dejun Chen, Shangjian Zhang, Yong Liu, Zhiyong Zhong, and Charles M. Falco N