Organic single crystals are promising materials for low cost and room temperature direct radiation detectors and personal dosimeters for medical application. An important issue is the investigation of electrical transport properties to understand the radiation-organic material interaction and the detection mechanism. Organic crystals are especially interesting for studying the intrinsic properties of molecular ordered structures. Solution-grown single crystals of hydorxycyanobenzene(4HCB) are electrically characterized before and after X-ray irradiation. The current- voltage characteristics show the activation of a different transport regime under X-ray beam, similar to a trap-free behavior, while the dark current has space-charge limited characteristic, typical of dielectric and most organic semiconductor. In the framework of SCLC analyses, and of the Nespurek-Sworakowsky model, is it possible to estimate the energy and density distribution of traps. We observe in 4HCB crystals a localized band of states located at about Et ≈ 0,49eV that completely disappears under X-ray irradiation. The hypothesis we make is that the free charge carriers induced under irradiation completely fill the crystal trap states, thus explaining the trap-free trend in current-voltage characteristic under x-ray.
X-ray radiation effects on organic single crystals
CIAVATTI, ANDREA;FRABONI, BEATRICE;
2013
Abstract
Organic single crystals are promising materials for low cost and room temperature direct radiation detectors and personal dosimeters for medical application. An important issue is the investigation of electrical transport properties to understand the radiation-organic material interaction and the detection mechanism. Organic crystals are especially interesting for studying the intrinsic properties of molecular ordered structures. Solution-grown single crystals of hydorxycyanobenzene(4HCB) are electrically characterized before and after X-ray irradiation. The current- voltage characteristics show the activation of a different transport regime under X-ray beam, similar to a trap-free behavior, while the dark current has space-charge limited characteristic, typical of dielectric and most organic semiconductor. In the framework of SCLC analyses, and of the Nespurek-Sworakowsky model, is it possible to estimate the energy and density distribution of traps. We observe in 4HCB crystals a localized band of states located at about Et ≈ 0,49eV that completely disappears under X-ray irradiation. The hypothesis we make is that the free charge carriers induced under irradiation completely fill the crystal trap states, thus explaining the trap-free trend in current-voltage characteristic under x-ray.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
