Frequency dependent electrical characteristics of PbS quantum dots S. Chowdhury, A. M. P. Hussain, G. A. Ahmed and A. Choudhury Eur. Phys. J. Appl. Phys., 42 2 (2008) 113-119 Published online: 09 April 2008 DOI: 10.1051/epjap:2008043