One-carrier thermally stimulated currents and space-charge-limited currents in naphthalene crystals: Doped and irradiated samples.

Abstract

Measurements of space-charge-limited currents (SCLC) and thermally stimulated currents (TSC) were done in naphthalene single crystals grown from the melt and also from solution. Crystals grown from the melt were irradiated with x rays to a dose that ranged between 8×104 and 6×106 R. These crystals were also doped with beta naphthol with concentrations that varied from 10−4 to 10−2 in mole fraction. Melted crystals showed a trap level at 0.71 eV using SCLC and 0.79 eV using TSC, whereas solution crystals showed 0.43 eV using SCLC and 0.78 eV using TSC. Irradiated samples showed a trap level at 0.50 eV. In the case of doped samples the impurities originate a trap level at a depth of 0.53 eV that was possible to predict theoretically. Results showed that care must be exercised to obtain a valid comparison between the SCLC and TSC measurements and also that trapping of charge carriers is greatly influenced by the conditions under which the crystals were grown.