Enhancing the thermoelectric performance of ZnO film by sputter-deposition of Ag nanoparticles

Abstract

Owing to the surface plasmon resonance (SPR), noble metal nanoparticles (NPs) have been intensively employed to improve the optical properties of semiconductors. In this work, Ag NPs are deposited on fully c-axis oriented ZnO film with high-crystallinity prepared by radiofrequency magnetron sputtering on glass substrates. After Ag sputtering of 15 s, the ultraviolet light emission intensity of ZnO film significantly is increased by 50% due to the SPR of Ag NPs. Moreover, the conductive behavior changes from n-type semiconductor to metal-like with room-temperature conductivity sharply increasing by nearly three orders of magnitude from 4.8 for pure ZnO film to 3400 S cm ^−1 for Ag-deposited ZnO film. The change of conductive behavior and the remarkable increase of the conductivity can be ascribed to isolated Ag NPs with high-density electrons which are distributed on the ZnO film, leading to an increase of carrier concentration that exceeds Mott’s critical density (>10 ^19 cm ^−3 ). Hall measurements show that after Ag sputtering of 15 s, the mobility increases from about 8 to 40 cm ^2 V ^−1 s ^−1 and that the carrier concentration increases from 4 × 10 ^18 to 5 × 10 ^20 cm ^−3 . Owing to the remarkable improvement of the conductivity, the power-factor value at room temperature is enhanced from 11.5 to 49.2 μ Wm ^−1 K ^−2 .

Keywords

• ZnO film
• thermoelectric
• Ag nanoparticles
• carrier concentration