Evolution and Recovery of Electrical Property of Reactive Sputtered Al‐Doped ZnO Transparent Electrode Exposed to Harsh Environment

Machda, Fahmi; Ogawa, Takahira; Okumura, Hideyuki; Ishihara, Keiichi N.

doi:10.1002/pssa.201900519

Cited by 3 publications

(3 citation statements)

References 26 publications

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“…Furthermore, before the damp heat test, the carrier concentration of AZO-15/60 was higher than AZO-3/60 that could lead to higher durability. This result is in line with the findings reported by Machda et al 30 where higher carrier concentration contributes to better durability of AZO films. Despite that both are having main crystal orientation (110), fewer crystal orientations of AZO-3/60 as compared to AZO-15/60 could contribute to this different level of decrease in Hall mobility.…”

Section: Resultssupporting

confidence: 93%

Damp Heat Durability of Al-Doped ZnO Transparent Electrodes with Different Crystal Growth Orientations

Machda¹,

Ogawa²,

Okumura³

et al. 2019

ECS J. Solid State Sci. Technol.

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Al-doped ZnO (AZO) transparent electrodes deposited by reactive sputtering are investigated to clarify the influences of crystal orientations on film durability. During the deposition, argon gas flow was varied from 3 to 60 sccm amidst fixed oxygen gas flow at 60 sccm. With increasing argon gas flow, the crystal orientations exhibit a major transition from ( 110) to (002). During damp heat test at 85% relative humidity and 85°C, the films with more variations in crystal orientations exhibit more decreased Hall mobility, while the films having crystal orientation (002) exhibit less reduced carrier concentrations. Conductivity degradation over time is monotonous with argon gas flow, and the tendency is more similar to reduced carrier concentrations rather than decreased mobility. It is suggested that the degradation differences among AZO films are rather caused by the effectiveness of major crystal orientation in protecting carrier concentrations.

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Section: Resultssupporting

confidence: 93%

Damp Heat Durability of Al-Doped ZnO Transparent Electrodes with Different Crystal Growth Orientations

Machda¹,

Ogawa²,

Okumura³

et al. 2019

ECS J. Solid State Sci. Technol.

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“…Owing to its non-toxic nature as well as abundance in the Earth's crust, impurity-doped ZnO has become a very promising alternative TCO material [13][14][15][16]. Taking into account the fact that the tetrahedral covalent radii of Al (∼123 pm) is nearly equal to that of Zn (∼122.5 pm) as well as the low ionization energy of Al Zn in ZnO (∼57 meV) [15], Al is an ideal n-type dopant for ZnO that can lead to rather low resistivity (ρ) of ∼1 × 10 −4 Ω cm.…”

Section: Introductionmentioning

confidence: 99%

“…Although AZO can readily reach a low ρ ∼ 10 −4 Ω cm, its chemical/thermal stability is typically inferior to other TCOs (e.g. ITO, SnO 2 ), and this is a major issue to be overcome for its wide applications [14,[20][21][22]. The chemical instability of AZO is mainly related with the formation of Zn(OH) 2 and Znbased carbonates at the grain boundaries due to the reaction of the AZO with water and CO 2 molecules from the environment [20], while the thermal instability is linked to diffusion of point defects as well as the formation of new phases and defects [23].…”

Section: Introductionmentioning

confidence: 99%

Effects of oxygen flow ratio and thermal annealing on defect evolution of aluminum doped zinc oxide thin films by reactive DC magnetron sputtering

Liu

Egbo

et al. 2021

J. Phys.: Condens. Matter

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Al doped ZnO (AZO) is a promising transparent conducting oxide to replace the expensive Sn doped In2O3 (ITO). Understanding the formation and evolution of defects in AZO is essential for its further improvement. Here, we synthesize transparent conducting AZO thin films by reactive DC magnetron sputtering. The effects of oxygen flow ratio as well as the rapid thermal annealing (RTA) in different conditions on their structural and optoelectrical properties were investigated by a variety of analytical techniques. We find that AZO thin films grown in O-rich conditions exhibit inferior optoelectrical performance as compared with those grown in Zn-rich conditions, possibly due to the formation of excessive native acceptor defects and/or secondary phases (e.g. Al2O3). Temperature-dependent Hall measurements indicate that mobilities of these highly degenerate AZO films with N > 1020 cm−3 are primarily limited by ionized and neutral impurities, while films with relatively low N ∼ 1019 cm−3 exhibit a temperature-activated mobility owing to the grain-barrier scattering. As N increases, the optical band gap of AZO thin film increases as a result of Burstein–Moss shift and band gap narrowing. RTA treatments under appropriate conditions (i.e. at 500 °C for 60 s in Ar) can further improve the electrical properties of AZO thin film, with low resistivity of ∼6.2 × 10−4 Ω cm achieved, while RTA at high temperature with longer time can lead to the formation of substantial sub-gap defect states and thus lowers the electron mobility. X-ray photoelectron spectroscopy provides further evidence on the variation of Al (Zn) content at the surface of AZO thin films with different processing conditions.

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Defect-dependent environmental stability of high mobility transparent conducting In-doped CdO

Wu,

Zha,

Zhang

et al. 2024

Journal of Applied Physics

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Highly degenerate n-type CdO with high electron mobility is a promising transparent conducting oxide (TCO) for optoelectronic devices utilizing a spectrum in the Vis-NIR range. In particular, it has been shown that doped CdO thin films can show much superior transparency of >80% in the NIR region compared to conventional transparent conducting oxide (e.g., Sn-doped In2O3) thin films with a similar sheet resistance. However, CdO thin films typically experience rapid degradation in their electron mobilities when exposed to environmental conditions with H2O moisture. Here, we studied the effects of thermal annealing on the environmental stability of In-doped CdO (CdO:In) using a combination of different analytical techniques. CdO:In thin films with different In concentration (0%–8.3%) synthesized by magnetron sputtering were subjected to different post-thermal annealing (PTA) and then aged in different environmental conditions with varying relative humidity (RH) in the range of 0%–85%. Our results reveal that the degradation of CdO:In thin films can be primarily attributed to the oxygen vacancy-related defects at the grain boundaries, which can readily react with the OH− in the moisture. The moisture induced degradation can be mitigated by appropriate PTA at high temperatures (>400 °C) where grain boundary defects, primarily associated with Cd vacancies, can be passivated through hydrogen (H), thus enhancing their environmental stability. The present study provides a comprehensive understanding of the instability mechanisms and defect passivation in transparent conducting CdO:In thin films, which can also be relevant for other wide gap oxides.

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Evolution and Recovery of Electrical Property of Reactive Sputtered Al‐Doped ZnO Transparent Electrode Exposed to Harsh Environment

Cited by 3 publications

References 26 publications

Damp Heat Durability of Al-Doped ZnO Transparent Electrodes with Different Crystal Growth Orientations

Damp Heat Durability of Al-Doped ZnO Transparent Electrodes with Different Crystal Growth Orientations

Effects of oxygen flow ratio and thermal annealing on defect evolution of aluminum doped zinc oxide thin films by reactive DC magnetron sputtering

Defect-dependent environmental stability of high mobility transparent conducting In-doped CdO

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