Basic knowledge of gadolinium oxysulfide (GOS) amorphous silicon detectors

Differences between different X-ray detectors. Gadolinium oxysulfide (GOS) amorphous silicon detector consists of a scintillator or phosphor layer coated with an amorphous silicon layer (used as a photodiode). The scintillator is required to convert X-rays into visible light, which is then converted by the photosensitive element. The visible light is converted into electrical signals, and then the imaging is switched through the TFT array. This is also indirect digital photography.

Based on the scintillation crystal coating material, amorphous silicon detectors are generally divided into two main types: cesium iodide (CsI) amorphous silicon detectors and gadolinium oxysulfide (GOS) amorphous silicon detectors. The imaging principles of the two detectors are basically the same, but in terms of performance, cesium iodide has a needle-like crystal structure, and the overall conversion efficiency of X-rays into visible light is higher than that of gadolinium oxysulfide coating. Speckle dispersion is also smaller. Therefore, by using cesium iodide as the scintillator material, the X-ray dose is smaller and the imaging is clearer. However, since the gadolinium oxysulfide coating does not require a long deposition process, the preparation process of gadolinium oxysulfide is simple and low-cost. The production cost of cesium iodide amorphous silicon detectors is higher than that of gadolinium oxysulfide amorphous silicon detectors, so in general, gadolinium oxysulfide-coated cesium iodide amorphous silicon detectors are preferred. ​

Sensitive to long wavelength light of 550 nm. Therefore, its technology can increase the imaging brightness of the gadolinium oxysulfide amorphous silicon detector by 30%, achieving the imaging effect of the cesium iodide amorphous silicon detector. And its production cost is lower than the latter, and it has considerable market application prospects. Food safety has always been a major issue related to life and health. In the field of food production and processing, rapid and accurate detection of foreign matter in food, including metal, glass, plastic, bone and other high-density impurities, is the key to ensuring product quality control. X-ray detection is widely used in this field, and can quickly image and locate foreign objects in assembly line operations and handle them accordingly.

Gadolinium oxysulfide (GOS) amorphous silicon detectors are formed by coating amorphous selenium on a TFT array. Compared to amorphous silicon detectors, it does not require a scintillation crystal to convert X-rays into visible light. When X-rays hit the amorphous selenium layer, electron-hole pairs are created. These electrons and holes will move in opposite directions under the action of an external bias field, forming a current. The current is integrated in the TFT to form stored charges. By reading the charge, the X-ray dose at each point can be known.

Therefore, the gadolinium oxysulfide (GOS) amorphous silicon detector is more direct to digital photography than the amorphous silicon detector and can completely avoid the loss of clarity caused by scattering during the conversion of X-rays into visible light. But its disadvantage is that its bias electric field is as high as several thousand volts. The high-voltage electric field will cause damage to the TFT switch and reduce its service life. And the production cost is also higher than amorphous silicon detectors.