High quality transparent TiO2/Ag/TiO2 composite electrode films deposited on flexible substrate at room temperature by sputtering

Aritra Dhar,T L Alford

doi:10.1063/1.4808438

Abstract

Multilayer structures of TiO2/Ag/TiO2 have been deposited onto flexible substrates by room temperature sputtering to develop indium-free transparent composite electrodes. The effect of Ag thicknesses on optical and electrical properties and the mechanism of conduction have been discussed. The critical thickness (tc) of Ag mid-layer to form a continuous conducting layer is 9.5 nm and the multilayer has been optimized to obtain a sheet resistance of 5.7 Ω/sq and an average optical transmittance of 90% at 590 nm. The Haacke figure of merit (FOM) for tc has one of the highest FOMs with 61.4 × 10−3 Ω−1/sq.

Highlights

A-ITO film deposited on flexible substrates has some limitations such as fairly lower conductivity owing to low process temperature and reduced dopant activation at lower temperatures
Promising alternative materials include pure SnO2, ZnO, or ZnO doped with metals (i.e., aluminum (Al), gallium (Ga), etc.), Nb2O5, TiO2, graphene, and carbon nanotube (CNT) sheets have been recently studied as potential alternatives to amorphous indium tin oxide (a-ITO) electrodes on flexible substrates.[5,6,7,8,9]
Insertions of a very thin metal layer sandwiched between the two transparent conducting oxide (TCO) layers have been studied to develop a transparent composite electrode (TCE) with the desired electrical conductivity.[9,10,11,12]

Summary

Introduction

Can be used as optical coatings on large area substrates for architectural, automotive and display applications and protective layers for very large-scale integrated circuits.[14,15,16] In this work, the high transparency of TiO2 in visible region and low resistivity of thin Ag layer lead us to the detailed study of optical and electrical properties of TiO2/Ag/TiO2 (TAT) multilayer as TCEs. The multilayer transparent conductive electrodes have been deposited onto flexible substrates by sputtering at room temperature. A more detailed investigation of Fig. 2 shows that the effective resistivity of the TAT multilayers drops significantly from 5 to 7 nm and indicates the presence of small Ag island structures in case of 5 nm deposition.

Results

Conclusion