Correlated barrier hopping in CdS nanoparticles and nanowires

The ac conduction in CdS nanoparticles and nanowires was investigated in the frequency range 10(2) to 10(6) Hz and in the temperature range 303-573K. The behavior of ac conductivity was found to agree with that reported for amorphous materials and doped semiconductors. The values of ac conductivities were found to be higher than those reported for bulk CdS. The experimental results were analyzed with the CBH model proposed by Elliott. This model provided reasonable values for the maximum barrier height and characteristic relaxation time. The electrical properties of CdS nanowires and nanoparticles were compared. It was also found that the concentration of charged defect centers was large in nanowires and nanoparticles and it tended to decrease with an increase in temperature. The density of neutral defect, formed by the conversion of charged defects was also calculated. The defects in both types of nanostructures were studied by photoluminescence spectroscopy. It was found that nanoparticles possessed higher defect density than nanowires. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3569744]