Origin of Low-Energy Spurious Peaks in Spectroscopic Measurements With Silicon Detectors

When an uncollimated radioactive X-ray source illuminates a silicon PIN sensor, some ionizing events are generated in the nonimplanted gap between the active area of the sensor and the guard rings (GRs). Carriers can be collected by floating electrodes, i.e., electron accumulation layers at the silicon/oxide interface, and floating GRs. The crosstalk signals generated by these events create spurious peaks, replicas of the main peaks at either lower amplitude or of opposite polarity. We explain this phenomenon as crosstalk caused by charge collected on these floating electrodes, which can be analyzed by means of an extension of Ramo theorem.