Diffusion and defects in semiconductors: from fundamentals to applications

Following a general trend in miniaturization, there is an urgent need in quantitative knowledge of basic atomic-level processes associated with processing of both conventional and especially novel materials in a wide variety of applications in micro- and nanoelectronics. Gaining a better understanding of such processes as diffusion and associated defects interactions in technologically important materials is a prerequisite for device fabrication on a nanometer scale.
The proposed research program addresses these challenging tasks and consists of the following topics: (i) Diffusion in semiconductor materials employing radioactive ion implantation. The main interest lies on materials and diffusing species having significant importance in novel microelectronics and spintronics applications. A paramount aim of the research is to reveal the atomic mechanisms behind the diffusion processes. (ii) Proton irradiation induced point defects in compound semiconductors studied by positron annihilation spectroscopy (PAS) at low temperatures. An important goal of the research is to improve the understanding of the mechanisms generating ion irradiation induced point defects and to study their thermal behavior in representative materials of prime interest. These results provide also pertinent information needed in the diffusion mechanism related research. (iii) Radiation hardness of silicon based particle detectors affects directly the life span of sophisticated large-scale detector systems of modern high-energy physics experiments at CERN. To enable studies revealing the microscopic origin of the performance degradation of silicon particle detectors used in harsh radiation environment a new and unique experimental setup has been constructed. The facility makes feasible irradiation at cryogenic temperatures and particle detector current-voltage measurements combined with the online PAS and the possibility for optical ionization of the vacancies.
The project outcome will be exploited in many ways as understanding diffusion and defect interactions is a key issue for tailored engineering of materials on a nanoscale. Advanced radiation hardness of silicon detectors will extend their operational period which has a significant effect also on financial costs, e.g. in ultra-large scale detector arrays. The diverse research program can be realized only by taking advantage of the unique modified radiotracer method and on-line irradiation/positron annihilation spectroscopy facility available in the Accelerator Laboratory. Within the project students and researchers will be trained at an international research forum.