Transparent Conductive p-Type Cuprous Oxide Films in Vis-NIR Region Prepared by Ion-Beam Assisted DC Reactive Sputtering

Hui Sun,Tsung-Yen Kuo,Song-Sheng Lin,Fen Liu,Ming-Jiang Dai,Qian Shi,Wan-Xia Wang,Sheng-Chi Chen

doi:10.3390/coatings10050473

Abstract

Cu2O thin film has been widely studied due to its intrinsic p-type conductivity. It can be used as p-type transparent conductive electrode or hole transport layer in various potential applications. However, its intrinsic p-type conductivity is very limited, which needs to be optimized by introducing acceptor defects. In this work, the electrical properties of the Cu2O films was improved through introducing interstitial oxygen in the films those were deposited via direct current sputtering assisted by oxygen ion beam. The results show that with oxygen ion beam current increase, the carrier concentration effectively improves. However, with more interstitial oxygen introduced, the film’s crystallinity significantly reduces, as well as the carrier mobility decreases. Meanwhile, all of the Cu2O films present moderate transmittance in the visible region (400–800 nm), but ideal transmittance in the near infrared (NIR) light region (800–2500 nm). When compared with the strong reflection of the n-type transparent conductive film to the near infrared light, the Cu2O film is transparent conductive in NIR region, which expands its application in the fabrication of NIR electrical devices.

Highlights

The transparent conductive oxides (TCOs) combined high optical transmittance and ideal electrical conductivity are widely used in various fields, for example, flat panel displays, touch screens, transparent electrodes, and so on [1,2,3]
The Cu2 O films were deposited by reactive magnetron sputtering under Ar + O2 atmosphere
With the oxygen ion beam current (IO2 ) increase, the crystallinity of Cu2 O film degrades. This is primarily due to more defects of interstitial oxygen being introduced into the film

Summary

Introduction

The transparent conductive oxides (TCOs) combined high optical transmittance and ideal electrical conductivity are widely used in various fields, for example, flat panel displays, touch screens, transparent electrodes, and so on [1,2,3]. The currently widely used TCO are mostly n-type semiconductors, such as SnO2 :F (FTO), In2 O3 :Sn (ITO), ZnO:In,Ga (IGZO), etc. [4,5,6] Their transmittance in the visible region can reach more than 85%, while their conductivity can achieve. In the near infrared (NIR) region (800–2500 nm), the transmittance of these n-type TCOs drops sharply [7,8]. The transmittance of ITO decreases rapidly beyond 1200 nm, its band gap is higher than 3.0 eV [9]. This severely restricts the application of transparent conductive materials in Coatings 2020, 10, 473; doi:10.3390/coatings10050473 www.mdpi.com/journal/coatings

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