Novel Carrier Doping Mechanism for Transparent Conductor: Electron Donation from Embedded Ag Nanoparticles to the Oxide Matrix

A trade-off between the Carrier concentration and carrier mobility is an inherent problem of traditional transparent conducting oxide.(TCO) films. In this study, we demonstrate that the electron concentration of TCO films can he increased without the carrier mobility by embedding Ag nanoparticles (NPs) into, Al-doped-ZtiO (AZO), films. An increment of Ag NP content up to 0.7 vol % in the AZO causes the electron concentration rising to 4 X 10(20) cm(-3). A dependence of the conductivity on temperature suggests that the energy barrier for the electron donation from Ag NPs at room temperature is similar to the Schottky barrier height at the Ag-AZO interface. In spite of an increase in the electron concentration, embedded Ag NPs do not compromise the carrier mobility at room temperature. This evidence, showing that this electron donation mechanism by Ag NPs is different from impurity doping which produces both electrons and ionized scattering centers; Instead, an increase in-the Perini energy level of the,AZO matrix partially neutralizes.A1 impurities,, and the-carrier mobility of Ag NP embedded AZO film is slightlyincreased: The optical transmittance of mixture films with resistivity less than 1 x 10(-3) acm still maintains abnve 85% in visible wavelengths. This opens a new paradigm to the design of alternative TCO composite materials which circumvent an inherent problem of the impurity doping.