Vacancy cluster in ZnO films grown by pulsed laser deposition

Wang, Zilan; Luo, Ching Hsing; Anwand, W.; Wagner, A.; Butterling, Maik; Rahman, M. Azizar; Phillips, M. R.; Ton-That, Cuong; Younas, Muhammad; Su, Shichen; Ling, Francis Chi‐Chung

doi:10.1038/s41598-019-40029-3

Cited by 31 publications

(22 citation statements)

References 37 publications

(61 reference statements)

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“…However, the interplanar distance slightly reduces when the annealing temperature further increases to 800 °C, possibly due to the creation of new vacancy defects. Zn out-diffusion at similar annealing temperature (900 °C) has been observed by other group [40][41][42]. Oxygen out-diffusion may be another possible reason for the decrease of interplanar distance as inferred from the XPS results.…”

Section: Resultssupporting

confidence: 79%

“…Another possible reason for the increase of refractive index can be the enhancement in crystallinity as indicated by the XRD and scanning electron microscopy (SEM) results. However, annealing at 800 °C might cause out-diffusion of zinc or oxygen atoms, leading to the decrease of refractive index [ 40 , 41 , 42 ]. The optical band gap ( E g ) was also calculated from the refractive index at 630 nm according to the following model [ 43 ]: n 2 = 1 + [13.6/( E g + 3.4)] 2 …”

Section: Resultsmentioning

confidence: 99%

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Suppression of Oxygen Vacancy Defects in sALD-ZnO Films Annealed in Different Conditions

et al. 2020

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Zinc oxide (ZnO) has drawn much attention due to its excellent optical and electrical properties. In this study, ZnO film was prepared by a high-deposition-rate spatial atomic layer deposition (ALD) and subjected to a post-annealing process to suppress the intrinsic defects and improve the crystallinity and film properties. The results show that the film thickness increases with annealing temperature owing to the increment of oxide layer caused by the suppression of oxygen vacancy defects as indicated by the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) spectra. The film transmittance is seldom influenced by annealing. The refractive index increases with annealing temperature at 300–700 °C, possibly due to higher density and crystallinity of the film. The band gap decreases after annealing, which should be ascribed to the decrease in carrier concentration according to Burstein–Moss model. The carrier concentration decreases with increasing annealing temperature at 300–700 °C since the oxygen vacancy defects are suppressed, then it increases at 800 °C possibly due to the out-diffusion of oxygen atoms from the film. Meanwhile, the carrier mobility increases with temperature due to higher crystallinity and larger crystallite size. The film resistivity increases at 300–700 °C then decreases at 800 °C, which should be ascribed primarily to the variation of carrier concentration.

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Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Suppression of Oxygen Vacancy Defects in sALD-ZnO Films Annealed in Different Conditions

et al. 2020

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“…There is strong evidence that interstitial hydrogen, H i , plays a role of donor [ 6 , 8 ], while hydrogen molecule, H 2 , has been shown to be electrically inert in ZnO [ 9 , 10 ]. However, recent investigations strongly suggest that hydrogen impurity in ZnO material may be involved in a number of complexes with native point defects, such as V Zn ·nH, Zn i ·V O ·H, and others [ 2 , 3 , 4 , 5 , 11 , 12 , 13 , 14 ]. Some of these complexes introduce shallow donor and acceptor levels that affect the resulting ZnO conductivity [ 4 , 10 , 15 , 16 , 17 , 18 ].…”

Section: Introductionmentioning

confidence: 99%

Structural Properties of Thin ZnO Films Deposited by ALD under O-Rich and Zn-Rich Growth Conditions and Their Relationship with Electrical Parameters

et al. 2021

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The structural, optical, and electrical properties of ZnO are intimately intertwined. In the present work, the structural and transport properties of 100 nm thick polycrystalline ZnO films obtained by atomic layer deposition (ALD) at a growth temperature (Tg) of 100–300 °C were investigated. The electrical properties of the films showed a dependence on the substrate (a-Al2O3 or Si (100)) and a high sensitivity to Tg, related to the deviation of the film stoichiometry as demonstrated by the RT-Hall effect. The average crystallite size increased from 20–30 nm for as grown samples to 80–100 nm after rapid thermal annealing, which affects carrier scattering. The ZnO layers deposited on silicon showed lower strain and dislocation density than on sapphire at the same Tg. The calculated half crystallite size (D/2) was higher than the Debye length (LD) for all as grown and annealed ZnO films, except for annealed ZnO/Si films grown within the ALD window (100–200 °C), indicating different homogeneity of charge carrier distribution for annealed ZnO/Si and ZnO/a-Al2O3 layers. For as grown films the hydrogen impurity concentration detected via secondary ion mass spectrometry (SIMS) was 1021 cm−3 and was decreased by two orders of magnitude after annealing, accompanied by a decrease in Urbach energy in the ZnO/a-Al2O3 layers.

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“…In contrast, a similar yellow emission attributed to Li impurities in ZnO is not passivated by an equivalent hydrogen plasma treatment [46].…”

Section: Zinc Interstitialsmentioning

confidence: 96%

Dopants and Impurity-Induced Defects in ZnO

Rahman¹,

Phillips²

2020

Defects in Functional Materials

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In recent years, there has been resurgent interest in ZnO due to its efficient UV emission and potential application in opto-electronic devices.The problem of self-compensating defects, especially those related to acceptor-like dopants, remains a major challenge to date. In this chapter, we provide an overview of the fundamental properties of point defects and dopants as well as their complexes in bulk crystals and nanostructures. Nominally undoped ZnO is typically n-type, which has been widely ascribed to O vacancies or Zn interstitials; however, these defect assignments are controversial as O vacancies are deep donors while Zn interstitials are highly mobile at room temperature and considered to be unstable. Accordingly, H and group III impurities have also been suggested to be responsible for the observed n-type conductivity. Although there are still many unanswered questions concerning defect-related luminescence bands in ZnO, great progress has been made in recent years to identify and characterize them using spatially resolved luminescence spectroscopies and first-principles calculations. The ubiquitous green emission has several possible origins, including O and Zn vacancies as well as Cu impurities. The properties of group I (Li, Na, and Cu), group III (Ga, Al, 177 March 4, 2020 19:49 Defects in Functional Materials 9in x 6in 1st Reading b3851-ch06 page 178 178 M. A. Rahman, M. R. Phillips & C. Ton-That and In), and group V (N, P, and Sb) impurities as well as their complexes with native point defects and H are discussed, along with a concluding outlook for future research into the optical properties of ZnO.

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Vacancy cluster in ZnO films grown by pulsed laser deposition

Cited by 31 publications

References 37 publications

Suppression of Oxygen Vacancy Defects in sALD-ZnO Films Annealed in Different Conditions

Suppression of Oxygen Vacancy Defects in sALD-ZnO Films Annealed in Different Conditions

Structural Properties of Thin ZnO Films Deposited by ALD under O-Rich and Zn-Rich Growth Conditions and Their Relationship with Electrical Parameters

Dopants and Impurity-Induced Defects in ZnO

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