Doping Mechanism of Ge4+ Ions in Ge4+‐Doped TiO2

Han, Zhongxing; Yu, Yanlong; Cao, Yaán

doi:10.1002/pssb.201700289

Cited by 6 publications

(4 citation statements)

References 31 publications

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“…In parallel, we also undertook XPS measurement of the as‐prepared crystals to examine the chemical valance of the Ge atoms, the binding energy of Ge 3d peak at 33.8 eV provides clear evidence to support the existence of Ge 4+ in the crystals. [ 38 ] From these results, we then can draw a solid conclusion that the 2D Ge‐TCNQ complex crystals are successfully synthesized based on the proposed synthesis route.…”

Section: Resultsmentioning

confidence: 93%

2D Metal‐Organic Complex Luminescent Crystals

Pei

Zhao

et al. 2021

Adv Funct Materials

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2D emissive crystals have attracted tremendous research interests due to their outstanding compatibility with an integrated planar photonic system, which ideally meet the requirement for versatile photonic device applications, such as lasers, light-emitting devices, and optical waveguides. Among 2D emissive materials, metal-organic complex crystals are highly desirable because of their strong charge-transfer interactions and enhanced optical absorption that benefit superior luminescence efficiency. Here, the in-air sublimation method is adopted to synthesize 2D Ge-TCNQ microplate crystals (TCNQ, 7,7,8,8-tetracyanoquinodimethane) with thickness down to 13.4 nm. Such ultrathin Ge-TCNQ crystals exhibit an exciton binding energy of 40.7 meV and a decent photoluminescence (PL) quantum efficiency of 5.53%. The fitting slope of excitation power-dependent PL intensity displays a transition from linear to superlinear characteristics that reveals both trap-assisted recombination and free carrier recombination are present in the luminescence process. The energy band structure of Ge-TCNQ is examined by ultraviolet photoelectron spectroscopy and UV-vis spectroscopy to elucidate the physical mechanism of photo excitation and fluorescence processes. The emissive Ge-TCNQ crystals are further employed as high-performance optical waveguides with a small optical loss coefficient of 0.078 dB µm −1 . This work opens new avenues using 2D metal-organic complex crystals to develop advanced optoelectronic devices.

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Section: Resultsmentioning

confidence: 93%

2D Metal‐Organic Complex Luminescent Crystals

Pei

Zhao

et al. 2021

Adv Funct Materials

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“…It is evident from figure 9 that the shape of the VB spectra in the mixed Ti doped a-GeO 2 changes continuously from a-GeO 2 to a-TiO 2 . Since the ionic radius of Ti 4+ is 68 pm and that of the Ge 4+ is 54 pm [48], substituting Ti in place of Ge effectively decreases the average O-O separation [46,49,50]. It is this separation of the oxygen atoms that is responsible for the broadening of the O 2p nonbonding band and results in the broadening of the VB spectra due to the incorporation of Ti atoms [46,49].…”

Section: Resultsmentioning

confidence: 99%

Unveiling the cation ratio mediated structural modifications in TiO₂:GeO₂ mixtures for gravitational-wave detectors

Bhowmick,

Osovsky,

Davenport

et al. 2024

Class. Quantum Grav.

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Amorphous thin films of Ti doped GeO2 are of interest for coatings of the mirrors in gravitational wave detectors due to their low internal friction (Phys. Rev. Lett 127 071101). The addition of Ti to a-GeO2 enables tailoring of the optical and structural properties of the mixtures. However, the specific modifications that occur in the amorphous network with the addition of Ti are not known. In this work, x-ray photoelectron spectroscopy is used to identify modifications to the bonding of Ge and Ti atoms in mixtures of Ti doped a-GeO2 with different Ti cation content. The formation of (Ti-O-Ge) bonds is evidenced from: 1) the presence of a peak which intensity increases with Ti content and causes a shift to lower binding energy of the core level O 1s peak; 2) the shift to higher binding energy of the Ti 2p3/2 peak and a decrease in the energy split; and 3) the shift to lower binding energy of the Ge 3d5/2 peak and increase in the energy split. These changes reflect modifications to the bonding when Ge replaces Ti in Ti-O-Ti bonds and viceversa in Ge-O-Ge bonds due to their difference in electronegativity. A decrease in the O-O nearest-neighbour distance due to the incorporation of Ti atom is also observed from the broadening of the valence band spectra. The results also show the Ti doped a-GeO2 mixture with 0.44 Ti cation concentration has an optimum balance between mixed network (Ti-O-Ge) and pure (Ge-O-Ge)/(Ti-O-Ti) networks than Ti poor and Ti rich mixtures. This finding could have important consequences in the optimization of amorphous Ti doped a-GeO2 mixtures for low internal friction coatings of gravitational wave detectors.

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“…[30] The systematic blue shift in this peak is assigned to the increased disorder in the structure of GeO 2 as a result of insertion and increasing the thickness of Ag 2 O nanosheets. The ionic radius of Ag þ1 being 128 pm [31] is much larger than that of Ge þ4 (54 pm [13] ), indicating the inability of Ag to fill vacant sites of germanium. In addition, vacant sites of oxygen (140 pm [32] ) can behave as deep trapping sites for positrons.…”

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confidence: 98%

“…However, it is mentioned that the accumulation of positively charged ions around oxygen atoms in SiO 2 is more pronounced than the accumulation around oxygen atoms in GeO 2 [12] for cations having the same ionic radius. The ionic radius of germanium ion being 54 pm [13] is the same as that of Si þ4 (54 pm). [14] This property indicates that compared with Ge-O, stronger coulombic interaction between Si and O is expected.…”

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confidence: 99%

Effects of Ag₂O Nanosheets on the Structural, Optical, and Dielectric Properties of GeO₂ Stacked Layers

Alharbi

Qasrawi²,

Algarni

2021

Physica Status Solidi (b)

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Germanium dioxide is an attractive material that can be used in the design of optoelectronic devices. As for example, thin films of GeO 2 , which are prepared by the sputtering technique, are found to be suitable for photonic applications including waveguides. [1] In addition, Ge/GeO 2 -reduced graphene oxide composites are nominated as promising materials for use in high-performance lithium-ion batteries. [2] The incorporation of GeO 2 into these batteries enhanced the reversible capacity and forced good cycling stability. Moreover, GeO 2 is nominated as a promising material for visible light photodetection, [3] lightemitting devices, [4] and as memristors. [5] As a photovoltaic material, when exposed to light irradiation of wavelength 540 nm and power of 0.20 mW cm À2 , GeO 2 displayed a photoresponse of %100 times with an external quantum efficiency of 17% under a reverse-biased voltage of À2.0 V. [3] As light-emitting materials, GeSi x O y films containing germanium nanoclusters displayed photoluminescence signals in the spectral range of 1400-1600 nm. [4] Memristors made of GeO[SiO 2 ] and GeO[SiO] films on Si substrates are mentioned, exhibiting features that nominate them for the fabrication of neuromorphic devices. [5] Various doping agents were used to enhance the optoelectronic performances of germanium dioxide glasses. Bismuth doping into the structure of GeO 2 -SiO 2 glasses, which are used in fiber optics, is mentioned, enhancing the photostability of laser-active centers (generated by bismuth) under pumping at 1550 nm at different temperatures. [6] When illuminated with 805 nm pump lasers (1.6 mW), neodymium-doped GeO 2 -PbO glasses are observed to have a high relative gain of 3.6 dB cm À1 . This property makes the GeO 2 -PbO glasses good candidates for use in the fabrication of amplifiers and lossless components. [7] The wide range of applications of GeO 2 -SiO 2 and GeO 2 -PbO glasses motivated us to form a new class of glasses composed of GeO 2 -Ag 2 O. Yet the literature data that concern the effect of insertion of silver oxide nanosheets between stacked layers of germanium dioxide are absent. As silver oxide exhibits energy bandgap of E g ¼ 1.20 eV and work function of qϕ ¼ 5.47 eV, [8] interfacing it with wide-bandgap GeO 2 (E g ¼ 5.30 eV, qϕ > 7.5 eV [9] ) may engineer the optical properties of GeO 2 and make it more appropriate for visible light detection. Thus, here in this work, we will report the effect of insertion of Ag 2 O nanosheets of thicknesses 25-75 nm between stacked layers of GeO 2 (each of thickness 500 nm) and explore the changes in the optical transmittance, reflectance, absorption coefficient, light absorbability, energy band tails, dielectric constant, and optical conductivity. The study is conducted by the X-ray diffraction (XRD), scanning electron microscopy (SEM), and visible-infrared (IR) light spectrophotometry.

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Doping Mechanism of Ge⁴⁺ Ions in Ge⁴⁺‐Doped TiO₂

Cited by 6 publications

References 31 publications

2D Metal‐Organic Complex Luminescent Crystals

2D Metal‐Organic Complex Luminescent Crystals

Unveiling the cation ratio mediated structural modifications in TiO₂:GeO₂ mixtures for gravitational-wave detectors

Effects of Ag₂O Nanosheets on the Structural, Optical, and Dielectric Properties of GeO₂ Stacked Layers

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Doping Mechanism of Ge4+ Ions in Ge4+‐Doped TiO2

Cited by 6 publications

References 31 publications

2D Metal‐Organic Complex Luminescent Crystals

2D Metal‐Organic Complex Luminescent Crystals

Unveiling the cation ratio mediated structural modifications in TiO2:GeO2 mixtures for gravitational-wave detectors

Effects of Ag2O Nanosheets on the Structural, Optical, and Dielectric Properties of GeO2 Stacked Layers

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Product

Resources

About

Doping Mechanism of Ge⁴⁺ Ions in Ge⁴⁺‐Doped TiO₂

Unveiling the cation ratio mediated structural modifications in TiO₂:GeO₂ mixtures for gravitational-wave detectors

Effects of Ag₂O Nanosheets on the Structural, Optical, and Dielectric Properties of GeO₂ Stacked Layers