Irradiation effects in semiconducting diamonds

Effects of X-ray, β and UV irradiation on semiconducting diamonds (type IIb) were studied and compared with those induced at the same conditions in natural (type Ia) and in synthetic diamonds. Methods of optical absorption, of X-ray and light induced luminescence, of thermoluminescence (TL) as well as of optically stimulated luminescence and optically stimulated thermoluminescence (OSL and OSTL) were used for the investigations. The IIb diamonds showed in the UV a weak absorption band at 260nm and a sharp increase of absorption below 230nm, while in the Ia samples the absorption increased sharply below 300nm and absorption bands appeared near 310, 385 and 415nm. In the X-ray induced luminescence of all samples an emission band appeared near 440nm; in the Ia samples, additional band was recorded near 500nm and a very weak one at about 360nm. In all samples TL could be excited by X-ray, β as well as by 360-nm UV radiation; and in the IIb diamond also by 225 and 470nm. In the TL of IIb diamonds main emission bands appeared at 475 and 665nm, and in the OSTL of the Ia samples at 650nm. The thermal activation energies were evaluated and found to be of about 0.36, 0.52 and 0.67eV at the 360, 420 and 520K peaks, respectively. The main TL peaks appeared in all samples above RT at the same temperatures and with the same thermal activation energies. The results indicate that these TL peaks are due to the same radiation induced trapping levels in all investigated types of diamonds, while in the emission of the various samples different luminescence centers are involved. The TL reached in all investigated samples saturation for relatively low radiation doses.