Papers by Keyword: Photoconductivity

Abstract: Recently peaceful use of the nuclear energy and radioactive nuclides has increased the radiation pollution factor in the world and radiation safety problems have become actual ones. The development of the nuclear power engineering, protection and processing of radioactive wastes of nuclear reactors, the use of radioactive isotopes in national economy, nuclear explosion, industrial wastes and etc. may cause the radioactive pollution of the environment. In the case of such pollution the environment as well as living organisms are exposed to radioactive radiation (a-, b-, γ- etc.). Radioactive substances emit radioactive rays and as their decay time varies for natural and artificial radioactive substances the time of their environmental effect ranges from some years to million years.

Abstract: We present photoconductivity experiments on a 4H-SiC diode and on 4H-SiC high purity semi-insulating (HPSI) substrate. These devices have been tested over a wide optical wavelength range: 355 nm to 820 nm. The penetration depth of optical wavelength has been estimated from spectrophotometer measurements. Photoconductivity regime has been studied at low electrical field for both devices and photoconductivity efficiency has been compared to Si switches.

Abstract: Electrically active defects induced by ion implantation of boron and phosphorus into silicon and their recovery under isothermal annealing at 450 °C were investigated using Deep Level Transient Spectroscopy (DLTS) and Energy Resolved Tunneling Photoconductivity (ERTP) spectroscopy at cryogenic temperatures. DLTS results show electrically active deep traps located at Ev+0.35 eV and Ev+0.53 eV in boron implanted Si and at Ev+0.34 eV, Ev+0.43 eV, and Ev+0.38 eV in phosphorus implanted Si. These meta-stable defect sites were found to be either eliminated or significantly reduced in thermally annealed samples. We assigned these defect sites to hydrogen and carbon incorporated complexes formed during ion implantation. Corroborating the DLTS results, the photocurrent measurement also revealed a strong reduction of electrically active defects states, extended from EC – 0.3 eV up to the conduction band edge of Si, upon isothermal annealing.

Abstract: The polyaniline (PANI) coated titania (TiO2) has been prepared with ammonium persulfate (APS) as an oxidant in sodium dodecylsulfate(SDS) micellar aqueous solution. These nanosized powders could transfer into the organic phase. With increase in the amount of SDS, the dispersibility into the organic solvent was increased. Consequently, the electrical conductivity of the product was also decreased. The obtained composites showed 14.16 S/cm of conductivity at maximum while the value was almost independent on the polyaniline coating ratio in range of 100~20wt%. The conductivity value of composite with 20wt% polyaniline was 70000 times higher than that of raw titania. Modified titania had properties of polyaniline and titania together. In addition these composite showed the photoconductive response against the UV irradiation, which might show the existence of P-N junction between titania and polyaniline. The detailed structure and property analyses with X-ray, UV-spectroscopy, electron microscopy and so on will be discussed in relation to the synthetic conditions

Abstract: Single-wall Carbon nanotubes (SWNTs) bonded with dodecylamine groups were obtained by chemical modification. The modified SWNTs showed improved solubility in organic solvents. Both its chemical and aggregated structure was characterized by means of FTIR and TEM. The photoconductivity of oxotitanium phthalocyanine (TiOPc) doped with the modified SWNTs was investigated by xerographic photoinduced discharge method. The results showed that the photosensitivity of the double-layered photoreceptor composed of the SWNTs/TiOPc composite as charge generation material was higher than that of pristine TiOPc, and the sensitivity increased with the content of modified SWNTs in the composites. It is the photoinduced charge transfer between TiOPc and SWNTs that contributes to the improved photosensitivity of the modified SWNTs/TiOPc composites.

Abstract: In this paper superlinear dependence in the intensity–current characteristic, optical and temperature quenching of photocurrent and photoelectric memory in structures made on the basis of compensated 6H-SiC at room and high temperatures are reported. The maximal time of decreasing of the residual current was 5*104 s. With illumination by additional light with 0.62 μm wavelength and increasing of the applied voltage the value of residual current can be changed. The depth sensitivity centre is positioned at Ec -1.1eV and the cross section of captured holes on this centre is 10-21-10-22 cm2 based on our measurements.

Abstract: We investigated the influence of photoexcited nonequilibrium electrons in Bi4Ti3O12-d which contains a high density of oxygen vacancies. As increasing oxygen deficiency, the photocurrent undergoes a rapid enhancement, accompanied by a remarkable change of kinetics. In heavily oxygen deficient Bi4Ti3O12-d (d=0.45), we observed dispersive photoconductivity, a behavior resembles with persistent photoconductivity phenomena in some perovskites. We argue that oxygen vacancies acting as trapping centers for electrons are linked to dispersive diffusion in the perovskite blocks, which control carrier recombination.

Abstract: In this study, X-ray detectors with coplanar metal-semiconductor-metal structure, were fabricated employing high quality chemical vapour deposited (CVD) diamond film grown by a direct current arc jet plasma system. In which the electrical contacts with dimension of 25 µm in width with a 25 µm inter-electrode spacing, were patterned on the growth side of the diamond film using lift-off technology. The performance of the fabricated detectors was evaluated by steady-state X-ray illumination. The photoconductivity of the diamond detectors was found to linearly increase with increase in the X-ray photon flux. This demonstrates that high quality CVD diamond can be used for X-ray detectors.