Tuning the band gap, electronic polarizability and conduction mechanism of DyxZn1−xO nanostructures: the role of band tail states

Abstract

We study the effect of varying band tail states on the electronic polarizability and conduction mechanism of the ZnO host matrix with varying Dy3+ concentration. The disorder caused by varying concentration of Dy3+ ions leads to change the local polarizability due to the charge redistribution and the mixing of cations in a host matrix. This results in varying coordination environment, leading to varying local density of states in the forbidden energy gap. The disorder induced intra gap localized states play a vital role in controlling the band gap, which varies between 2.7 and 2.9 eV in this study and determining the conduction mechanism. The nanoparticles were synthesized via wet chemical route. Phase identifications and local distortions were identified using x-ray diffraction and Raman spectroscopy analysis respectively. The strong E2(high) mode corresponding to the intrinsic ZnO is depressed substantially, which shows the mixing of two different cations in a host matrix. The band gap and band tail states were determined from the diffuse reflectance spectroscopy data. The changing behaviour regarding the relaxation and conductivity of the host material has been discussed using impedance spectroscopy.