First principles study and variable range hopping conductivity in disordered Al/Ti/Mn-doped ZnO

Subgap states in aluminium- and hydrogen-doped zinc-oxide thin-film transistors

“…2(a), (d), and (g) displays the temperature-dependent transfer characteristics of the ZnO TFTs with and without the top Al 2 O 3 layer at temperatures from 180 to 300 K. Charges in the disordered semiconductors transport through localized states via thermally activated hopping, showing an increase in the electrical current as the temperature increases. 30,31 The electrical currents of the pure and doped ZnO TFTs increase with increasing temperature. Thus, the charge transport behavior of the ZnO TFTs can be described by a thermally activated hopping model.…”

“…3(b) presents the total density of states (TDOS) of the ZnO films as a function of the number of Zn vacancies. Although the electronic bandgap of ZnO is slightly underestimated due to the well-known Kohn-Sham energy functionals, 24,30,41 it is clear that, as the number of Zn vacancies increases, the distance between the CBM and VBM increases. The shortened Zn-O bond lengths due to the removal of Zn atoms and the resulting upward shifts of the Zn S-band lead to an increase in the bandgap.…”

Maxwell–Wagner Polarization and Mixed Ferromagnetic and Antiferromagnetic State in Eu2CoMnO6

“…Below 200 K temperature, ρ ( T ) is fitted with the variable range hopping (VRH) model. [ 12,39,49–52 ] The equation relating the VRH is given as…”

“…[ 49 ] According to Mott criteria of the VRH model, W should be greater than thermal energy ( k B T ) and R should be such that αR > 1. [ 50 ] Table 1 summarizes the different VRH parameters of ECMO signifying the validity of Mott's criteria. At temperatures above 200 K, the ρ ( T ) best follows a thermally activated small polaron hopping (SPH), [ 53,54 ] due to an increase in drift mobility and hopping frequency of the carriers.…”

“…Below 200 K temperature, ρ(T ) is fitted with the variable range hopping (VRH) model. [12,39,[49][50][51][52] The equation relating the VRH is given as…”