The fabrication and characterization of direct conversion flat panel X-ray imager with TlBr film

The novel direct conversion flat panel detectors (FPDs) utilizing thallium bromide (TlBr) films are developed and characterized in this study. Thin TlBr films, deposited using an evaporation technique, achieved thicknesses of 10 mu m and 50 mu m. A pixel sensor array, with a pixel size of 235 x 235 mu m(2) and a sensitive area of 29.61 x 39.48 mm(2), was developed using low-temperature polysilicon thin-film transistor (LTPS TFT) technology as the initial study to explore performance characteristics of developed imaging system. The TlBr film was characterized based on the current-voltage (I-V) profile, showing a resistivity of 2.78 x 1010 Omega.cm. The LTPS TFT showed a leakage current of about 10-13 A, while the noise of TlBr FPD system was around 104 e(-) rms, primarily limited by the readout system. The detector system was characterized using radiation from an X-ray tube with a voltage in the range of 30 kV-100 kV and a current of 2 mA, involving an X-ray test chart as the object with the processing time of 18.15-18.30 ms per frame. Based on the contrast and contrast-to-noise ratio (CNR) values, the 10 mu m and 50 mu m TlBr FPD clearly captured the image in operation between 30 kV and 100 kV. The 50 mu m TlBr FPD demonstrated improved sensitivity, showing pixel values with 10 times higher intensity and enhanced line pair detail at 30 kV X-ray operation. The 10 mu m TlBr achieved spatial resolution of 267 mu m full width at half maximum (FWHM), while the 50 mu m TlBr achieved 250 mu m FWHM. In the X-ray imaging demonstration, the shape and structure of anchovy was clearly distinguished. The TlBr film FPD presents promising potential for a room temperature X-ray imager.