ZnO-Based Transparent Conductive Thin Films: Doping, Performance, and Processing

Yanli Liu,Haibo Zeng,Yufang Li

doi:10.1155/2013/196521

Yanli Liu, Haibo Zeng + Show 1 more

Open Access

https://doi.org/10.1155/2013/196521

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Abstract

ZnO-based transparent conductive thin films have attracted much attention as a promising substitute material to the currently used indium-tin-oxide thin films in transparent electrode applications. However, the detailed function of the dopants, acting on the electrical and optical properties of ZnO-based transparent conductive thin films, is not clear yet, which has limited the development and practical applications of ZnO transparent conductive thin films. Growth conditions such as substrate type, growth temperature, and ambient atmosphere all play important roles in structural, electrical, and optical properties of films. This paper takes a panoramic view on properties of ZnO thin films and reviews the very recent works on new, efficient, low-temperature, and high-speed deposition technologies. In addition, we highlighted the methods of producing ZnO-based transparent conductive film on flexible substrate, one of the most promising and rapidly emerging research areas. As optimum-processing-parameter conditions are being obtained and their influencing mechanism is becoming clear, we can see that there will be a promising future for ZnO-based transparent conductive films.

Highlights

Transparent conductive oxides (TCOs), capable of transporting electrical charge and transmitting visible photon, are necessary for use as transparent electrodes in flat panel displays such as liquid crystal displays (LCDs), plasma display panels, electronic paper displays, light-emitting-diodes (LEDs) [1], and touch panels [2, 3]
In comparison with Al3+, Ga3+ has similar ionic radius to Zn2+ ions, which minimizes the ZnO lattice deformations even at higher doping concentrations [18, 21]. This may explain the reason why the best electrical properties of ZnO-based films are observed in Ga-doped ZnO thin films [22]
The low electrical resistivity and wide band gap energy of Mg and Ga codoped ZnO thin films (MGZO) thin films can be ascribed to the dopant of Ga and Mg, respectively

Summary

Introduction

Transparent conductive oxides (TCOs), capable of transporting electrical charge and transmitting visible photon, are necessary for use as transparent electrodes in flat panel displays such as liquid crystal displays (LCDs), plasma display panels, electronic paper displays, light-emitting-diodes (LEDs) [1], and touch panels [2, 3]. ZnO thin films are a promising alternative to the commonly used ITO, which are low cost, nontoxic, highly durable against hydrogen plasma compared to ITO [11]. It has a more proper work function for the transparent contact cathode electrodes of transparent OLEDs [12]. Minami summed up the resistivity of impurity-doped binary compound TCO films reported among thirty years and found that the obtained minimum resistivity of impurity-doped ZnO films is still decreasing, while SnO2 and In2O3 films have essentially remained unchanged [4] Such trend indicates the possible significant promotion of ZnO-based TCO films. Whether we can optimize the fabrication of high-quality doped zinc oxide thin films at low cost determines the future of ZnO-based TCO films.

Different Dopant Elements

Doping Concentration

Effect of Growth Conditions

Findings

Summary