Silicon detectors: From radiation hard devices operating beyond LHC conditions to characterization of primary fourfold coordinated vacancy defects

The physics potential at future hadron colliders as LHC and its upgrades in energy and luminosity Super-LHC and Very-LHC respectively, as well as the requirements for detectors in the conditions of possible scenarios for radiation environments are discussed in this contribution.Silicon detectors will be used extensively in experiments at these new facilities where they will be exposed to high fluences of fast hadrons. The principal obstacle to long-time operation arises from bulk displacement damage in silicon, which acts as an irreversible process in the in the material and conduces to the increase of the leakage current of the detector, decreases the satisfactory Signal/Noise ratio, and increases the effective carrier concentration. These effects must be considered in the design of semiconductor detectors for high energy physics. A major difficulty in the prediction of these effects arises from the fact that there exists a good or reasonable agreement between theoretical models and data for the time evolution of the leakage current and effective carrier concentration after lepton and gamma irradiation, and discrepancies up to 2 orders of magnitude for leakage current and the time interval for inversion after hadron irradiation, and this in conditions where a reasonable accord is obtained between experimental and calculated concentrations of complex defects.In this paper, we argue that the consideration of the existence of the new defect - the fourfold coordinated defect (Si$_{\rm{FFCD}}$) could solve these discrepancies and also permits to estimate indirectly the characteristics of the defect.