Characterisation of a CMOS Active Pixel Sensor for use in the TEAM Microscope

TL;DR

This paper presents the design, characterization, and performance evaluation of CMOS active pixel sensors for electron microscopy, demonstrating high detection efficiency, spatial resolution, and radiation tolerance.

Contribution

The study introduces a monolithic CMOS sensor with detailed characterization and validation for electron microscopy, including a novel single-electron reconstruction technique.

Findings

Line spread function of 12.1 microns at 80 keV

Detection quantum efficiency of 0.78 at 80 keV

Radiation tolerance up to 5 Mrad with 30% dynamic range reduction

Abstract

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.