Evaluation of a Structured Cesium Iodide Film for Radiation Imaging Purposes


We describe the properties of evaporated layers of Cesium Iodide (Thallium activated) deposited on substrates that enable easy coupling to amorphous silicon pixel arrays. The CsI(Tl) layers range in thickness from 65 to 220 µm. We used the two-boat evaporator system to deposit CsI(Tl) layers. This system ensures the formation of the scintillator film with homogenous Tl concentration which is essential for optimizing the scintillation light emission efficiency. The Tl concentration was kept to 0.1-0.2 mole % for the highest light output. Temperature annealing can affect the microstructure as well as light output of the CsI(Tl) film. 200-300C0 annealing can increase the light output by a factor of two. The amorphous silicon pixel arrays are p-i-n diodes approximately 1 µm thick with transparent electrodes to enable them to detect the scintillation light produced by X-rays incident on the CsI(Tl). Digital radiography requires a good spatial resolution. This is accomplished by making the detector pixel size less than 50 ?m. The light emission from the CsI(Tl) is collimated by techniques involving the deposition process on pattered substrates. We have measured MTF of greater than 12 line pairs per mm at the 10% level.

Meeting Name

Proceedings of the 1993 IEEE Nuclear Science Symposium & Medical Imaging Conference


Mining and Nuclear Engineering

Document Type

Article - Conference proceedings

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© 1994 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.