A rad-hard CMOS active pixel sensor for electron microscopy

Monolithic CMOS pixel sensors offer unprecedented opportunities for fast nano-imaging through direct electron detection in transmission electron microscopy. We present the design and a full characterisation of a CMOS pixel test structure able to withstand doses in excess of 1 Mrad. Data collected with electron beams at various energies of interest in electron microscopy are compared to predictions of simulation and to 1.5 GeV electron data to disentagle the effect of multiple scattering. The point spread function measured with 300 keV electrons is (8.1±1.6)μm for 10μm pixel and (10.9±2.3)μm for 20μm pixels, respectively, which agrees well with the values of 8.4 and 10.5μm predicted by our simulation.