In several recent PA's, the NIH has articulated a clear vision for the future of medical imaging systems?a) enhanced spatial or temporal resolution, b) better sensitivity and specificity, c) multi-modality, and d) new functional or molecular imaging or spectroscopy methods. Owing to their unique combination of properties, direct conversion gamma radiation imaging CdZnTe (CZT) pixel array detectors have the potential to support most of the elements of this vision. However, today there does not exist a technology for commercial manufacturing of low-cost, high-spatial-resolution CZT imaging detectors that meets the requirements of system performance, fabrication cost, compatibility with detector assembly processes, and long-term device stability and reliability. If such a technology were readily available to researchers there would exist many opportunities for exploration of new imaging modalities using CZT imaging detectors. To achieve this objective, one of the most essential technologies in need of improvement is the fabrication of quality electrodes on CZT. Such electrodes today suffer from thermal and temporal instabilities, delamination, high levels of noise, incompatibility with commercial semiconductor assembly processes, lack of production scalability, and very high manufacturing costs. Therefore, our proposal is to develop improved, scalable CZT electrode fabrication technologies. To achieve this objective, we have assembled a strong team from industry and academia that brings together broad multidisciplinary expertise in CZT processing, surface and interfacial chemistry and radiation detector characterization. In contrast to past trial-and-error investigations, our effort is centered on intensive CZT surface and interfacial analysis, characterization and modification ') along with extensive candidate detector performance qualification testing.
The aim i s to improve charge collection efficiency, energy resolution, temperature stability, long-term stability and reliability, signal-to-noise ratio, adhesion, and scale-up manufacturability. Even if our program is only modestly successful, given the current state of CZT fabrication technology, we anticipate significant advancements, that will result in more readily available CZT detectors for investigators at lower cost having more reproducible and consistent performance. This will bring an urgently needed service to the imaging systems development community. If successful, the work will lead to advancements in imaging of minute cancerous tumors in internal organs, in the study of new drugs and their interaction in living tissues, and possibly in the study of the nervous system at much finer levels than possible today.
