Effect of heavy Ag doping on the physical properties of ZnO

Abstract

The band structure, density of state and absorption spectrum of Zn[Formula: see text]Ag[Formula: see text]O (x = 0.02778, 0.04167) were calculated. Results indicated that a higher doping content of Ag led to a higher total energy, lower stability, higher formation energy, narrower bandgap, more significant red shift of the absorption spectrum, higher relative concentration of free hole, smaller hole effective mass, lower mobility and better conductivity. Furthermore, four types of model with the same doping content of double Ag-doped Zn[Formula: see text]Ag[Formula: see text]O (x = 0.125) but different manners of doping were established. Two types of models with different doping contents of double Ag-doped Zn[Formula: see text]Ag[Formula: see text]O (x = 0.0626, 0.0833) but the same manner of doping, were also established. Under the same doping content and different ordering occupations in Ag double doping, the doped system almost caused magnetic quenching upon the nearest neighbor –Ag–O–Ag– bonding at the direction partial to the a- or b-axis. Upon the next-nearest neighbor of –Ag–O–Zn–O–Ag– bonding at the direction partial to the c-axis, the total magnetic moment of the doped system increased, and the doped system reached a Curie temperature above the room-temperature. All these results indicated that the magnetic moments of Ag double-doped ZnO systems decreased with increased Ag doping content. Within the range of the mole number of the doping content of 0.02778–0.04167, a greater Ag doping content led to a narrower bandgap of the doped system and a more significant red shift in the absorption spectrum. The absorption spectrum of the doped ZnO system with interstitial Ag also shows a red shift.