Study on the structure and properties of gallium bismuth oxide alloy thin films prepared by sol-gel method

• Published in: Journal of sol-gel science and technology Vol. 103; no. 1; pp. 280 - 289
• Main Authors: Zhang, Q., Deng, J. X., Li, R. D., Luo, J. X., Kong, L., Meng, J. H., Gao, H. L., Yang, Q. Q., Wang, G. S., Wang, X. L., Wang, J. Y.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.07.2022; Springer Nature B.V
• Subjects: Absorption spectra; Bismuth oxides; Bowing; Ceramics; Chemistry and Materials Science; Composites; Crystal structure; Crystallization; Curve fitting; Electronic structure; Energy gap; Ethylene glycol; Fourier transforms; Gallium oxides; Gamma phase; Glass; Infrared spectrometers; Infrared spectroscopy; Inorganic Chemistry; Materials Science; Monoclinic lattice; Monoethanolamine (MEA); Nanotechnology; Natural Materials; Optical and Electronic Materials; Optical properties; Original Paper: Sol-gel and hybrid materials for optical; Parameters; Photoelectrons; photonic and optoelectronic applications; Sol-gel processes; Spectrum analysis; Thin films; X ray photoelectron spectroscopy; Sol-gel; Bi; ); Ga; Band gap; Alloy; O
• DOI: 10.1007/s10971-022-05784-2
• ISSN: 0928-0707

(Bi x Ga 1-x ) 2 O 3 films were prepared at 820 °C by sol-gel method, an ethylene glycol solution of hydrated gallium nitrate and bismuth nitrate stabilized by monoethanolamine, of which crystallization, surface morphology and electronic structure as well as optical properties were studied in detail by X-ray diffraction, Scanning electron microscope-energy dispersive spectrometer, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and Ultraviolet-visible spectroscopy. XRD showed Ga 2 O 3 film prepared from solutions consisted of two crystal structures, β and γ, increasing Bi atoms into Ga 2 O 3 that enable the inhibition of γ phase formation and (Bi x Ga 1-x ) 2 O 3 and Ga 2 O 3 capable of holding the same monoclinic crystal structure. EDS displayed (Bi x Ga 1-x ) 2 O 3 films of varied compositions were obtained with content of different Bi atoms into the solution, which kept same monoclinic crystal as β-Ga 2 O 3 when Bi ranged from 0 < x < 0.056. FTIR revealed that the absorption band below 480 cm −1 corresponded to the octahedral position of Ga 2 O 3 and the Bi atoms in the (Bi x Ga 1-x ) 2 O 3 films substituted the Ga in the [GaO 6 ] octahedron. XPS exhibited increasing Bi content raised Ga 3+ /Ga ratio. UV-VIS provided evidence that optical band gap of (Bi x Ga 1-x ) 2 O 3 down to 3.2 eV indicating Bi-doping achieved Ga 2 O 3 band gap tunable, concurrently, the bowing parameter c  = 1.83 eV was obtained on the basis of the fitting curve of band gap. Combination monoclinic gallium oxide which has ultra wide band gap and a small amount of Bi 3+ by sol-gel method can form (Bi x Ga 1-x ) 2 O 3 alloy. Bi 3+ mainly replaces gallium at the octahedral position of gallium oxide, which lifts the valence band position and reduces the band gap of gallium oxide, and can transfer the optical absorption spectrum of gallium oxide from deep ultraviolet region to blue ultraviolet region. Highlights The addition of Bi can effectively inhibit the formation of γ-phase gallium oxide and change the cell parameters of gallium oxide. The range of Bi in bismuth gallium oxide alloy with monoclinic crystal structure is 0 < x < 0.056. Bi atoms mainly replace Ga in [GaO6] octahedron. Bi atoms increase the proportion of Ga 3+ /Ga in bismuth gallium oxide alloy. Increasing the content of Bi atoms effectively reduces the band gap of bismuth gallium oxide alloy.