Study On The Preparation Method Of A-Se Film In X-ray FPD

In recent years, digital Flat Panel X-Ray Detectors (X-Ray FPD), especiallydirect conversion type, becomes to be most popular in X-Ray radiography researchfield. The FPD is composed by Thin Film Transistors (TFT) arrays and photo-conductive sensors. The technology of TFT has been developed to a high level. Mostresearches in FPD field put emphasis on sensors. Amorphous-Selenium (a-Se) hasgreat photo-conductive properties such as high X-ray sensitivity and high spatialresolution etc. which greatly improve the imaging quality. Nowadays, the fabricationand characteristic analysis of high performance and large area a-Se alloy film are thefocus of research in this field.Technological basis about digital X-Ray FPD and also theoretical basis abouta-Se are described in this paper. From compare of direct type and indirect type ofFPD and the physical and electrical properties of, the performance predominance ofthe a-Se alloy film is proved. As, amorphous Selenium alloy films are alwaysprepared by vacuum evaporation. Vacuum physics basis and vacuum evaporationmethod are discussed to give advice and direction to the experiment's design.In this paper, Arsenic (As) is adopted as the doped chemical element to fabricatea-Se alloy to avoid self-crystalline. The As-Se alloy film is deposited by high vacuumresistor heating evaporation method. A new high vacuum film plating set developedbased on a set of vacuum aluminum plating appliance will be introduced in details.The research of preparation has gone through two stages, which worked out twokinds of a-Se films differ in size. Test on thickness distribution, amorphous degreeand basal electric characters are designed and deployed to those a-Se experimentalfilms which proved to be satisfied with the basic requirement of photoconductivematerials.