Effect of O2/Ar Gas Flow Ratios on Properties of Cathodic Vacuum Arc Deposited ZnO Thin Films on Polyethylene Terephthalate Substrate

Chien-Wei Huang,Cheng-Tang Pan,Min-Hang Weng,Ru-Yuan Yang

doi:10.1155/2016/6479812

Abstract

Cathodic vacuum arc deposition (CVAD) can obtain a good quality thin film with a low growth temperature and a high deposition rate, thus matching the requirement of film deposition on flexible electronics. This paper reported the room-temperature deposition of zinc oxide (ZnO) thin films deposited by CVAD on polyethylene terephthalate (PET) substrate. Microstructure, optical, and electrical measurements of the deposited ZnO thin films were investigated with various O2/Ar gas flow ratios from 6 : 1 to 10 : 1. The films showed hexagonal wurtzite crystal structure. With increasing the O2/Ar gas flow ratios, thec-axis (002) oriented intensity decreased. The crystal sizes were around 16.03 nm to 23.42 nm. The average transmittance values in the visible range of all deposited ZnO films were higher than 83% and the calculated band gaps from the absorption data were found to be around 3.1 to 3.2 eV. The resistivity had a minimum value in the 3.65 × 10−3 Ω·cm under the O2/Ar gas flow ratio of 8 : 1. The luminescence mechanisms of the deposited film were also investigated to understand the defect types of room-temperature grown ZnO films.

Highlights

During the last few decades, flexible electronics such as thinfilm transistors, solar cells, and light-emitting diodes have been studied intensively owing to their advantages of light weight and low cost over present rigid electronics [1]
We reported a detailed investigation on the effects of various O2/Ar gas flow ratios on properties of pure zinc oxide (ZnO) films deposited by using Cathodic vacuum arc deposition (CVAD) on the polyethylene terephthalate (PET) substrate at a room temperature and investigated the relation between the microstructure, optical, and electrical properties by using Xray diffraction (XRD), ultraviolet-visible spectroscopy (UVVIS), Hall measurement, a four-point probe, and photoluminescence (PL)
The PET substrates were loaded into the CVAD chamber with a substrateanode distance of approximately 21 cm, and the chamber was evacuated to 10−5 Torr by a rotary and diffusion pump arrangement in the depositions of ZnO films

Summary

Introduction

During the last few decades, flexible electronics such as thinfilm transistors, solar cells, and light-emitting diodes have been studied intensively owing to their advantages of light weight and low cost over present rigid electronics [1]. The high polymer flexible substrate, such as polyethylene terephthalate (PET), polycarbonate (PC), polyethersulfone (PES), polyethylene naphthalate (PEN), or polyimide (PI) [3,4,5] are commonly used for the above flexible applications. Deposition of such TCO films on the plastic substrates requires a lowtemperature technique since most of polymer substrates could not be used above 200∘C. Low temperature deposition becomes the most important issue for growing high quality TCO films on flexible polymer substrates [1]

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Discussion

Conclusion