Defect controlled space charge limited conduction in CdS nanostructured sandwich structure

Abstract

A defect induced space charge limited conduction mechanism in PVP capped CdS, CdS:Mn and CdS/ZnS nanostructured films has been discussed in this research paper. XRD confirms the hexagonal structure for core CdS and CdS:Mn nanostructure and a mixed type structure for CdS:Mn and CdS/ZnS core–shell nanostructure which agrees with HRTEM measurement. The optical properties shows average band gap around 2.3 eV. The current–voltage (I-V) characteristics of Cu/Film/Cu sandwich exhibit nearly ohmic behaviour at low bias, while at high it become trap induced space-charged limited conduction (SCLC), followed by trap free square law. A quantitative assessment has been done analysing the SCLC mechanism. The shallow traps owing to Mn doping and shelling, found within 0.15 eV to 0.20 eV may exponentially distributed above the electron Fermi level 0.24 eV. The free carrier density, total trap density, trap cross-section, escape frequency are estimated and co-related to growth.