LARGE AREA DETECTOR FOR X-RAY DIFFRACTION STUDIES

NEW TECHNIQUES FOR DIGITAL X-RAY IMAGING HAVE BEEN UNDER INVESTIGATION FOR DECADES. SOME OF THE MOST PROMISING TEECHNIQUES INCORPORATE SOLID-STATE X-RAY DETECTORS, WHICH ARE ATTRACTIVE BECAUSE OF THEIR COMPACTNESS. HIGH-Z SEMICONDUCTOR X-RAY DETECTORS HAVE FURTHER ADVANTAGES DUE TO THEIR HIGH STOPPING POWER. ONE OF THE DRAWBACKS OF HIGH-Z SEMICONDUCTOR DETECTORS IS THE COST OF PRODUCING LARGE-AREA ARRAYS. THE USUAL APPROACH IS TO ASSEMBLE AN ARRAY OF ISOLATED, INDIVIDUALLY-FABRICATED DETECTOR ELEMENTS. A COMPETING TECHNOLOGY IS TO ENHANCE LARGE AREA ARRAYS OF AMORPHOUS SILICON (A-SI) PHOTODIODES BY COATING THEM WITH A FILM OF HIGH-Z SCINTILLATING MATERIAL (E.G., CSI) BY EVAPORATION. WHILE THIS TECHNIQUE IS MORE EFFECTIVE IN STOPPING X-RAYS THAN USING "NAKED" SILICON PHOTODIODES, THE POOR CONVERSION EFFICIENCY OF SCINTILLATORS LIMITS THE SIGNAL AMPLITUDE. RESEARCHERS ARE PRODUCING SUBLIMED FILMS OF A NEW, HIGH-Z SEMICONDUCTOR (THALLIUM BROMIDE), AND CHARACTERIZING THEIR UTILITY AS PIXILATED DETECTORS FOR X-RAY IMAGE DETECTION. MEASUREMENTS OF SUBLIMED TIBR FILMS ARE MADE AND NOTED THAT THESE DETECTORS MAINTAIN SURPRISINGLY GOOD CHARGE CARRIER TRANSPORT PROPERTIES IN SPITE OF THEIR POOR CRYSTALLINITY. THESE FILMS ARE READ OUT BY DEPOSITING THEM ON AN AMORPHOUS SILICON THIN-FILM TRANSISTOR ARRAY. THESE DETECTORS YIELD A LARGER SIGNAL THAN THE SCINTILLATOR-ENHANCED DETECTORS, DUE TO THEIR HIGH CONVERSION EFFICIENCY WHILE MAINTANING HIGH X-RAY STOPPING POWER.