Structural optical and electrical properties of a transparent conductive ITO/Al-Ag/ITO multilayer contact

Aliyu Kabiru Isiyaku; Ahmad Hadi Ali; Nafarizal Nayan

doi:10.3762/bjnano.11.57

Structural optical and electrical properties of a transparent conductive ITO/Al-Ag/ITO multilayer contact

Beilstein J Nanotechnol. 2020 Apr 27:11:695-702. doi: 10.3762/bjnano.11.57. eCollection 2020.

Authors

Aliyu Kabiru Isiyaku^{1

2}, Ahmad Hadi Ali¹, Nafarizal Nayan³

Affiliations

¹ Optical Fiber Laser Technology Group, Department of Physics and Chemistry, Faculty of Applied Sciences and Technology Pagoh Educational Hub, University Tun Hussein Onn Malaysia, 84600 Pagoh, Johor, Malaysia.
² Department of Physics, Faculty of Science, Kaduna State University, P.M.B 2339, Kaduna State, Nigeria.
³ Microelectronic and Nanotechnology Shamsuddin Research Centre (MiNT-SRC), Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia.

Abstract

Indium tin oxide (ITO) is a widely used material for transparent conductive oxide (TCO) films due to its good optical and electrical properties. Improving the optoelectronic properties of ITO films with reduced thickness is crucial and quite challenging. ITO-based multilayer films with an aluminium-silver (Al-Ag) interlayer (ITO/Al-Ag/ITO) and a pure ITO layer (as reference) were prepared by RF and DC sputtering. The microstructural, optical and electrical properties of the ITO/Al-Ag/ITO (IAAI) films were investigated before and after annealing at 400 °C. X-ray diffraction measurements show that the insertion of the Al-Ag intermediate bilayer led to the crystallization of an Ag interlayer even at the as-deposited stage. Peaks attributed to ITO(222), Ag(111) and Al(200) were observed after annealing, indicating an enhancement in crystallinity of the multilayer films. The annealed IAAI film exhibited a remarkable improvement in optical transmittance (86.1%) with a very low sheet resistance of 2.93 Ω/sq. The carrier concentration increased more than twice when the Al-Ag layer was inserted between the ITO layers. The figure of merit of the IAAI multilayer contact has been found to be high at 76.4 × 10^-3 Ω^-1 compared to a pure ITO contact (69.4 × 10^-3 Ω^-1). These highly conductive and transparent ITO films with Al-Ag interlayer can be a promising contact for low-resistance optoelectronics devices.

Keywords: DC sputtering; RF sputtering; annealing; figure of merit; indium tin oxide (ITO); multilayer structure.

Grants and funding

The support from Universiti Tun Hussein Onn Malaysia, Ministry of Higher Education Malaysia and Kaduna State University, Nigeria are gratefully acknowledged. This research was partially funded by the Fundamental Research Grant Scheme FRGS (Vot. No 1600) and Incentive Grant Scheme for Publication IGSP (U670).