This thesis presents a study of charge collection properties and its dependence on displacement damage caused by irradiation in CMOS detector prototypes developed for the phase-II upgrade of the Inner Tracker (ITk) in ATLAS experiment. Investigated samples were developed in four separate development lines and manufactured in different industrial processes. The main design parameters studied in this work are initial resistivity and the size of collection electrode. Samples were irradiated with reactor neutrons to fluences between 1e13 n_eq/cm^2 and 1e16 n_eq/cm^2 and with protons to fluences between 1e14 neq/cm2 and 3.6e15 n_eq/cm^2. Charge collection in the samples was characterized with Edge-TCT, radioactive 90Sr beta source and in a highly energetic pion test beam. Measurements of effective space charge concentration with Edge-TCT show significant radiation dependence influenced by initial acceptor removal. Acceptor removal is slower at lower initial substrate resistivity and is typically finished at a fluence of ~ 1e13 n_eq/cm^2 in highly resistive 2 k? cm material and ~ 1e15 n_eq/cm^2 in material with initial resistivity of 20?cm. Acceptor removal may cause the increase of the depth of depletion zone in certain range of fluences which was observed by both Edge-TCT and 90Sr. Measurements of in-pixel hit detection efficiency with test beam revealed significant efficiency gaps on pixel edges in samples with a small collection electrode after irradiation. These results prompted modifications of pixel design in form of additional implanted structures which are expected to significantly improve detector performance.
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