  A 1M- and a 4M-pixel monolithic CMOS active pixel sensor with 9.5x9.5
micron^2 pixels have been developed for direct imaging in transmission electron
microscopy as part of the TEAM project. We present the design and a full
characterisation of the detector. Data collected with electron beams at various
energies of interest in electron microscopy are used to determine the detector
response. Data are compared to predictions of simulation. The line spread
function measured with 80 keV and 300 keV electrons is (12.1+/-0.7) micron and
(7.4+/-0.6) micron, respectively, in good agreement with our simulation. We
measure the detection quantum efficiency to be 0.78+/-0.04 at 80 keV and
0.74+/-0.03 at 300 keV. Using a new imaging technique, based on single electron
reconstruction, the line spread function for 80 keV and 300 keV electrons
becomes (6.7+/-0.3) micron and (2.4+/-0.2) micron, respectively. The radiation
tolerance of the pixels has been tested up to 5 Mrad and the detector is still
functional with a decrease of dynamic range by ~30%, corresponding to a
reduction in full-well depth from ~39 to ~27 primary 300 keV electrons, due to
leakage current increase, but identical line spread function performance.
