In the concept of the International Large Detector (ILD), developed for the International Linear Collider (ILC) a Time Projection Chamber (TPC) is envisaged as main tracking detector.Such gaseous detectors have to be equipped with amplification devices in order to enlargethe amount of charge, which is set free by ionization caused by traversing charged particles.Micro Pattern Gas Detectors (MPGDs) will be used in the ILD TPC as amplification stage. Inthis thesis, Gas Electron Multipliers (GEMs) – one specific MPGD species – are analyzed concerning various properties. Effective gains and energy resolutions are compared for GEM foilsproduced by different manufacturers. A good understanding of these observables is obtainedby interpretation of the results with the help of geometrical parameters. Height profile measurements of GEM foils have been performed for the first time and the impact of non perfectflat GEMs is analyzed, especially on dE/dx determination and drift field quality. The resultsemphasize the need of a flat installation of GEMs in TPCs. As a consequence, a new mountingdevice has been developed to ensure flatness and to provide a method to cover large readoutareas, as in the ILD TPC, by introducing the least possible amount of dead material into thedetector. The developed structure has been tested in a TPC protoype, taking cosmic muondata. The influence of the mounting on track reconstruction, single point resolution, trackingefficiency and dE/dx measurements is quantified. The developed mounting is applicable in alarge scale TPC, if some design considerations are taken into account
