Al-doped ZnO/Ag/Al-doped ZnO multilayer films with a high figure of merit

Abstract

In this study, we investigated the effects of the Al-doped ZnO (AZO)-layer thickness on the optical and electrical properties of AZO/Ag/AZO multilayer films deposited on glass substrates at room temperature. The optimal AZO/Ag/AZO (36nm/19nm/36nm) multilayer sample exhibited a transmittance of approximately 93% at 550nm. As the AZO-layer thickness increased from 9 to 45nm, the carrier concentration gradually decreased from 1.87×1022 to 6.36×1021cm−3, while the sheet resistance slightly increased from 3.86 to 4.47Ωsq−1 and the charge mobility increased from 24.15 to 25.42cm2V−1s−1. The samples had smooth surfaces with a root mean square (RMS) roughness ranging from 0.40 to 1.23nm. The Haacke figure of merit (FOM) was calculated for the samples as a function of the AZO-layer thickness. The optimal AZO/Ag/AZO multilayer film had the highest FOM of 99.9×10−3Ω−1.