@phdthesis{Stegler2020, author = {Stegler, Martin}, title = {Studies on the influence of mechanical stress on the properties of silicon sensor modules for the ATLAS Phase-II Upgrade}, doi = {10.26127/BTUOpen-5323}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-53230}, school = {BTU Cottbus - Senftenberg}, year = {2020}, abstract = {The subject of this thesis is the development and test of silicon strip detectors for the high luminosity upgrade of the tracking detector of the ATLAS experiment at the Large Hadron Collider. Special emphasis is devoted to the understanding of the impact of mechanical stress on the electrical properties and the particle detection performance of detector modules. First simulations were done to estimate the maximum expected stress on a sensor when operated at -30 °C within the future silicon strip tracking detector ITk, at ATLAS. The maximum stress in a worst case scenario is expected to be 27 MPa. Tensile strength tests were done to estimate the maximum stress which can be applied to a silicon strip sensor. Silicon shards, with a thickness and dopand concentration corresponding to the ITk sensor specifications break at >23 MPa, wafers at >700 MPa and sensors at ~ 400 MPa. The huge variations lead to the assumption, that the tensile stregth, which is highly dependent on the quality of the crystal lattice, is due to different cutting technology. Wafers, irradiated with a fluence equivalent of a lifetime dose of an ITk sensor, show no stress dependency of the youngs modulus. The tensile strength of irradiated wafers is decreased by ~ 6,6 \%. No damage on silicon sensors from mechanical stress is expected for sensor modules installed it the ITk. The electrical properties of silicon strip sensors were studied for applied mechanical stress on ATLAS07 sensors up to 60 MPa. The specifications of the sensors are similar to the specification of strip sensors in the future silicon strip tracker barrel region of the ATLAS detector. The leakage current changes at 50 MPa by -1.7 \%, the bias resistance by +0.8 \% and the interstrip resistance by -25 \%. The depletion voltage and the implant resistance are not affected by mechanical stress. Except for the interstrip resistance the results can be explained by piezoresistive effects. Silicon strip modules were build and studied in particle test beams. These modules consists of an ATLAS07 or an ATLAS12 sensor and an analogue readout to study the influence of stress on the module performance. The sensor module noise is independent from the applied stress. An effect of stress on the signal strength was seen. The ATLAS07 sensor module signal strength was decreased and the ATLAS12 sensor module signal strength was increased with a slope of ~0,6 MPa^-1. The average cluster size of the ATLAS07 sensor module was increased by 0,25 \% MPa^-1 and the average cluster size of the ATLAS12 sensor module was decreased by 0,06 \% MPa^-1 with applied stress.}, subject = {ATLAS; Piezoresistivity; Stress; Silicon; ITk; Silizium; Sensormodul; LHC; Silicium; Sensor; Piezowiderstand; ATLAS }, language = {en} }