However, it is important to mention that activation energy alone does not provide any information as to whether conduction takes place in the extended states above the mobility edge or by hopping in the localized states. This is due to the fact that both of these conduction mechanisms may take place simultaneously. The activation energy in the former case represents the energy difference between mobility edge and the Fermi level, E c − E F or

E F − E BV-6 purchase V, and in the latter case, it represents the sum of the energy GANT61 ic50 separation between the occupied localized states and the separation between the Fermi level and the mobility edge. It is evident from Table 1 that dc conductivity increases as the concentration of Cd increases, whereas the value of activation energy decreases with the increase in Cd contents in our lead chalcogenide nanoparticles. An increase in dc conductivity with a corresponding decrease in activation energy is found to be associated with a shift of the Fermi level for the impurity-doped chalcogenide [46, 61]. It also shows that the Fermi level changes after the incorporation of Cd. However, it has also been pointed out that the increase in conductivity could be caused by the increase in the portion

of hopping conduction BIX 1294 through defect states associated with the impurity atoms [62]. A clear distinction between these two conduction mechanisms can be made on the basis of the pre-exponential factor value. For conduction in extended states, the value of σ0 reported for a-Se and other Se alloys in thin films is of the order 104 Ω−1 cm−1[62]. In the present sample of a-(PbSe)100−x Cd x nanoparticles, the value of σ0 is of the order 107 Ω−1 cm−1. Therefore, extended state conduction is most likely to take place. An overall decrease in

the value of σ0 is observed with the increase in Cd contents in the PbSe system, which may be explained using the shift of Fermi level on adding Cd impurity. Therefore, the decrease in the value of σ0 may be due to the change in Fermi level on adding Cd in the PbSe System. Conclusions Thin films of amorphous (PbSe)100−x Cd x nanoparticles have been synthesized using thermal evaporation technique. The average diameter of these nanoparticles CYTH4 is approximately 20 nm. Raman spectra of these a-(PbSe)100−x Cd x nanoparticles revealed the presence of PbSe phases in as-synthesized thin films, and the observed wavelength shift in the peak position as compared with that of reported values on PbSe may be due to the addition of Cd impurity. PL spectra suggest that the peaks show a shift to the lower wavelength side as the metal (Cd) concentration increases, which may be attributed to the narrowing of the bandgap of a-(PbSe)100−x Cd x nanoparticles with the increase in cadmium concentration.