| Summary: | 碩士 === 輔仁大學 === 物理學系 === 97 === Cesium iodide (CsI) is a good scintillator due to its high luminescence efficiency. It was used for scintillation counter and photocathode in medical science and nuclear engineering because it can convert X-ray and γ-ray radiation into the visible light. However, its optical properties will become worse and luminescence-energy efficiency will be largely reduced due to easy moisture in CsI.
In this study, CsI films were deposited by ion beam assisted deposition (IAD) with homemade end-Hall ion source. The other material of sodium iodide (NaI) is a good scintillator and the NaI films were also studied. In order to investigate the enhancement of the luminescence-energy efficiency, CsI and NaI were mix-deposited onto fused silica substrates. In order to protect the films against moisture, SiO2 or Al was deposited onto the films. In order to increase the mobility of the depositing species and reduce the moisture, the substrate was heated from room temperature up to 300oC during deposition.
Using protective films preserved CsI films from deliquesce even after a month, but NaI films were not. In the luminescence-energy efficiency studies, it was found that the films deposited at 200oC were better than the films prepared at other temperatures. Furthermore, doping one percent NaI into the CsI films, the weight proportion of NaI to CsI was 1% wt to 99% wt, was the most brightness film in all mixed films. The most obvious luminescent wavelength excited by the mixed films had been turned from 390nm into 420nm when NaI was doped into the CsI films.
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