How are charge sharing and charge diffusion different?

An X-ray interaction in a semiconductor generates electron–hole pairs. The charge cloud drifts towards the collecting electrodes and may spread through diffusion and other processes. Charge sharing occurs when neighboring pixels collect charge from the same interaction.

Diffusion is one mechanism that broadens the cloud; sharing describes its collection by multiple pixels. The terms are related but are not interchangeable.

The extent of sharing depends on sensor thickness, pixel pitch, bias voltage, photon energy and interaction position. Thickness alone is therefore insufficient to compare detectors.

When pixels process signals independently, shared events can affect measured energy and counts. Medipix3 uses charge summing and allocation to mitigate these effects. Performance still depends on the acquisition mode, thresholds and sensor conditions.

Technical references: Subpixel resolution in CdTe Timepix3 pixel detectors; MÖNCH imaging study; CERN Medipix3.