Guard rings investigation of silicon sensors with modified pixel implant shapes in the context of the ATLAS experiment

Based on the standard design of the planar n + -in-n silicon pixel sensors of the innermost part of the tracking detector of the ATLAS experiment, six modified pixel designs were developed in Dortmund in order to increase the average electric field and thus the radiation hardness. The REINER pixel sensors contain these six modified pixel implantation shapes beside structures with the standard pixel design. Each pixel structure is provided by 13 guard rings and can be biased and investigated separately. This thesis aims to deeply investigate the electrical performances of the REINER sensors. The individual pixel designs have been cut from the original full REINER structure for the first time and a study of the single structures has been performed. The obtained results show that the cut sensors are broken and cannot be properly used anymore. These unexpected results that have been obtained hint at the investigation of the multi-guard ring structure of the implants in order to investigate the strength of the electric field at the edge of the sensor. The results show that the guard ring structure of each design properly works when a design is biased and its guard rings voltage measured. However, when the guard rings voltage is logged on another design, different from the biased one, the non-zero measurements proves that the pixel designs truly influence each other due to a non-ideal operation of the guard ring structure.