AbstractDiode detectors and silicon drift chambers were processed on TOPSIL high‐purity silicon of resistivity 7 kΩ cm. Their suitability for XRF spectroscopy, when cooled to −30°C, was evaluated. The efficiency for different x‐ray energies was calculated starting from the processing parameters used in manufacturing. Spectrum measurements were made in order to establish the mechanisms causing electrical noise and charge trapping. With an 18 mm2 active area detector it was possible to achieve an FWHM of 385 eV for the 55Fe source 5.89 keV peak and better than 300 eV with detectors of 1 mm2 area. Incomplete charge collection was found to be due to effects on the edge of the detector active area or in the implanted surface facing the radiation.