Characterization of standard and oxygenated float zone Si diodes under radiotherapy beams

The dosimetric response of silicon diodes made from high resistivity float zone (FZ) and diffusion oxygenated FZ (DOFZ) silicon has been studied with a 60Co clinical radiotherapy gamma source. To investigate the changes in sensitivity with the accumulated dose, the diodes have been exposed to doses of 137Cs gamma-rays up to 6 kGy. As expected, Si diodes showed a degradation in the signal response with the accumulated dose due to the formation of radiation-induced defects acting as lifetime killers. Nonetheless, the DOFZ Si diode appeared to be moderately radiation harder than the standard FZ sample, with a decay of sensitivity less pronounced.