Characterising the CMOS Image Sensor for the JANUS Camera on ESA’s JUICE Mission to Jupiter

Lofthouse-Smith, Daniel-Dee (2021). Characterising the CMOS Image Sensor for the JANUS Camera on ESA’s JUICE Mission to Jupiter. PhD thesis The Open University.



The subject of this thesis is the characterisation of a scientific Complementary Metal Oxide Semiconductor (CMOS) image sensor to be used on the JANUS camera on ESA’s JUICE mission to Jupiter.

The first part of this thesis investigates the initial characteristics of the device to better understand how changes in these characteristics manifest themselves over a range of tests.

Initially, following total ionising dose and displacement damage, an increase in the dark current is observed. At temperatures above room temperature, it is theorised that the dark current is proportional to the exponent of the band gap of silicon. Following thermal annealing of these irradiated devices a slight recovery in the average dark current is noticed, which can be credited to the annealing of some radiation induced defects.

The second part of this work investigates how image lag manifests in the image sensor, where a transitionary point to high level image lag is observed, referred to as the image lag ‘knee-point’. The signal that this knee point occurs is studied with varying total ionising dose and transfer gate voltages, allowing the cause to be hypothesised and an optimum operating condition to be recommended.

The image lag is also investigated on a pixel-by-pixel basis, which is a novel approach compared to the typical average level across the whole image sensor. Measurements with devices exposed to total non-ionising doses demonstrate the creation of a population of pixels that exhibit higher levels of image lag than average, an effect that has been attributed to displacement damage in the image sensor.

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