The role of Ga and Bi doping on the local structure of transparent zinc oxide thin films

JOURNAL OF ALLOYS AND COMPOUNDS

卷:870

Article

Correia, Filipe C.¹  Ribeiro, Joana M.¹  Kuzmin, Alexei²  Pudza, Inga²  Kalinko, Aleksandr^3,4  Welter, Edmund⁴  Mendes, Adelio⁵  Rodrigues, Joana^6,7  Sedrine, Nabiha Ben^6,7  Monteiro, Teresa^6,7  Correia, Maria Rosario^6,7  Tavares, Carlos J.¹ 

[1] Univ Minho, Ctr Phys, P-4710057 Braga, Portugal

[2] Univ Latvia, Inst Solid State Phys, LV-1063 Riga, Latvia

[3] Univ Paderborn, Dept Chem, Naturwissenschaftl Fak, Warburger Str 100, D-33098 Paderborn, Germany

[4] Deutsch Elektronen Synchrotron Res Ctr Helmholtz, Notkestr 85, D-22607 Hamburg, Germany

[5] Univ Porto, LEPABE, Fac Engn, Rua Roberto Frias S-N, P-4200465 Porto, Portugal

[6] Univ Aveiro, Dept Fis, P-3810193 Aveiro, Portugal

[7] Univ Aveiro, I3N, P-3810193 Aveiro, Portugal

关键词: Zinc oxide;    Thin films;    Sputtering;    Thermoelectric;    X-ray absorption spectroscopy;    Raman spectroscopy;   

DOI  :  10.1016/j.jallcom.2021.159489

来源: Elsevier

【 摘 要 】

Transparent undoped ZnO and additionally doped with Ga and Bi thin films were produced by magnetron sputtering. The thin films were comprehensively characterized by X-ray absorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission and scanning transmission electron (TEM, STEM) microscopy and Raman spectroscopy. All undoped and doped films crystallise in a ZnO phase with the hexagonal wurtzite crystal structure. The local structure of the thin films was investigated by temperaturedependent X-ray absorption spectroscopy at the Zn and Ga K-edges, as well as at the Bi L3-edge. It was found that the doping of Ga3+ and Bi3+ ions in the ZnO wurtzite structure produces distinct effects on the thin film microstructure. The substitution of Zn2+ ions by smaller Ga3+ ions introduces a static disorder to the thin film structure, which is evidenced by an increase in the mean-square relative displacements sigma(2)(Zn-O) and sigma(2)(Zn-Zn). At the same time, large Bi3+ ions do not substitute zinc ions, but are likely located in the disordered environment at the ZnO grain boundaries. This conclusion was directly supported by energy-dispersive X-ray spectroscopy combined with TEM and STEM observations as well as by resonant and non-resonant mu-Raman experiments at room temperature, where the ZnO and ZnO:Bi spectra are similar, suggesting a lack of structural disorder in the wurtzite cell. On the other hand, the Raman disorderactivated phonon is pronounced for Ga-doping of the ZnO lattice, confirming the compositional disorder. Both XRD and XPS ruled out Ga2O3 phase in Ga-doped ZnO; conversely, Bi2O3 and a small amount of Bi.metal phases are clearly discerned by XPS experiments, further suggesting that Bi is not incorporated in the ZnO wurtzite cell, but segregated to grain boundaries. (c) 2021 Elsevier B.V. All rights reserved.

【 授权许可】

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