Hellier Kaitlin, McGrath Molly, Abbaszadeh Shiva
Department of Electrical and Computer Engineering, University of California Santa Cruz, Santa Cruz, CA 95064, USA.
IEEE Sens J. 2024 Jun 15;24(12):19000-19006. doi: 10.1109/jsen.2024.3388972. Epub 2024 Apr 19.
Direct conversion X-ray detectors offer high spatial resolution and improved sensitivity over indirect conversion detectors. As interest increases in their applications, including utilization as the top layer in dual-layer detectors for polyenergetic X-ray detection, additional studies on fabrication techniques are required. Amorphous selenium is a well-studied high-Z semiconductor capable of high-resolution and high-sensitivity imaging in direct architectures. It is already commercially available for mammography, and much work has gone into developing it for higher-energy applications (>20 keV.) To fully attenuate energies required for the low energy (<35 keV) top layer in dual-layer detectors, a-Se thicknesses greater than 200 μm must be fabricated. However, evaporation crucibles have limited capacity and require reloading of crucible material to achieve higher thicknesses, which is performed by opening the chamber and breaking vacuum mid-fabrication. We investigate the effects of splitting the fabrication into two depositions - exposing the sample to air in between - on device performance. We find that there is no significant effect on the transport properties, and a small range of performance parameters can be found - suggesting small fluctuations between devices of ± 5%, independent of fabrication technique and thickness. This implies that as we increase our thicknesses to those required for the low-energy layer of the dual-layer detector, we can expect performance to be maintained.
直接转换X射线探测器比间接转换探测器具有更高的空间分辨率和更高的灵敏度。随着其应用领域的关注度不断提高，包括用作多能X射线检测双层探测器的顶层，需要对制造技术进行更多研究。非晶硒是一种经过充分研究的高Z半导体，能够在直接架构中实现高分辨率和高灵敏度成像。它已在乳腺摄影领域商业化应用，并且已经开展了大量工作以将其开发用于更高能量的应用（>20 keV）。为了完全衰减双层探测器中低能量（<35 keV）顶层所需的能量，必须制造厚度大于200μm的非晶硒。然而，蒸发坩埚的容量有限，需要重新装载坩埚材料以实现更高的厚度，这需要在制造过程中打开腔室并打破真空来完成。我们研究了将制造过程分成两次沉积——中间让样品暴露在空气中——对器件性能的影响。我们发现这对传输特性没有显著影响，并且可以找到一小范围的性能参数——这表明不同器件之间存在±5%的小波动，与制造技术和厚度无关。这意味着当我们将厚度增加到双层探测器低能量层所需的厚度时，可以预期性能将得以保持。
