Limits...
Fe(NO3)3-assisted large-scale synthesis of Si₃N₄ nanobelts from quartz and graphite by carbothermal reduction-nitridation and their photoluminescence properties.

Liu S, Fang M, Huang Z, Huang J, Ji H, Liu H, Liu YG, Wu X - Sci Rep (2015)

Bottom Line: The large-scale synthesis of Si3N4 nanobelts from quartz and graphite on a graphite-felt substrate was successfully achieved by catalyst-assisted carbothermal reduction-nitridation.The Fe(NO3)3 played a crucial role in promoting the nanobelt formation in the initial stage.The room-temperature photoluminescence spectrum of Si3N4 nanobelts consists of three emission peaks centered at 413, 437, and 462 nm, indicating potential applications in optoelectronic nanodevices.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Technology, Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, China University of Geosciences, Beijing, 100083.

ABSTRACT
The large-scale synthesis of Si3N4 nanobelts from quartz and graphite on a graphite-felt substrate was successfully achieved by catalyst-assisted carbothermal reduction-nitridation. The phase composition, morphology, and microstructure of Si3N4 nanobelts were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. The Si3N4 nanobelts were ~4-5 mm long and ~60 nm thick and exhibited smooth surfaces and flexible shapes. The Si3N4 nanobelts were well crystallized and grow along the [101] direction. The growth is dominated by the combined mechanisms of vapor-liquid-solid base growth and vapor-solid tip growth. The Fe(NO3)3 played a crucial role in promoting the nanobelt formation in the initial stage. The room-temperature photoluminescence spectrum of Si3N4 nanobelts consists of three emission peaks centered at 413, 437, and 462 nm, indicating potential applications in optoelectronic nanodevices.

No MeSH data available.


The emission spectra of Si3N4 nanobelts under 365 nm excitation (the black line is the as-obtained PL line, the red and green line is the simulated line).The top right corner is a simplified energy transitions between different energy levels.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4355634&req=5

f8: The emission spectra of Si3N4 nanobelts under 365 nm excitation (the black line is the as-obtained PL line, the red and green line is the simulated line).The top right corner is a simplified energy transitions between different energy levels.

Mentions: Fig. 8 shows the room-temperature PL spectrum of the Si3N4 nanobelts measured at the excitation of 365 nm (3.40 eV). As shown in the spectrum, three emission peaks were observed in the violet–blue spectral range: 413 nm (3.00 eV), 437 nm (2.84 eV), and 462 nm (2.69 eV). A comparison of the direct band gap of Si3N4 (5.0–5.3 eV) shows that the three peaks clearly did not arise from the energy transition between the valence and conduction bands. They can be attributed to the trap-level defects in the materials. Normally, Si3N4 has a tetragonal structure where the Si atom is tetracoordinated by the N atoms, and the N atoms are tricoordinated by the Si atoms34. It has been widely accepted that four types of defects are present in Si3N4: Si–Si and N–N bonds, and Si and N dangling bonds32. Furthermore, a bonding σ orbital and an antibonding σ* orbital were formed by the Si–Si bond, and the energy gap was ~4.6 eV3637. The dangling bonds also led to energy level splitting. The Si dangling bonds form one defect state in the midgap between these two orbitals marked as N3 ≡ Si*3538. The other two N defective states are called N4+ and N2°, generating the levels within the gap. Moreover, an unclear X level found by Zhang et al. was close to the N3 ≡ Si* level39. Based on a previous study, the PL behavior of the Si3N4 nanobelts can be explained by the model. The emission at 3.00 eV can be attributed to the recombination between the Si–Si σ* level and the N2° level or between the N4+ level and the valence-band edge. The peak at 2.84 eV can be attributed to the recombination from the N2° level to the X level. Huang et al. also reported a similar emission peak at 2.87 eV; however, they assumed that the presence of oxygen, which introduced the N–Si–O defective state in the gap, caused the emission ~2.8 eV21. As shown in the PL spectrum, the contribution from the 2.69 eV peak is much lower than the others. Thus, the double-photon absorption excitation from the valence edge to N3 ≡ Si* and then to the conduction edge may lead to the emission39.


Fe(NO3)3-assisted large-scale synthesis of Si₃N₄ nanobelts from quartz and graphite by carbothermal reduction-nitridation and their photoluminescence properties.

Liu S, Fang M, Huang Z, Huang J, Ji H, Liu H, Liu YG, Wu X - Sci Rep (2015)

The emission spectra of Si3N4 nanobelts under 365 nm excitation (the black line is the as-obtained PL line, the red and green line is the simulated line).The top right corner is a simplified energy transitions between different energy levels.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4355634&req=5

f8: The emission spectra of Si3N4 nanobelts under 365 nm excitation (the black line is the as-obtained PL line, the red and green line is the simulated line).The top right corner is a simplified energy transitions between different energy levels.
Mentions: Fig. 8 shows the room-temperature PL spectrum of the Si3N4 nanobelts measured at the excitation of 365 nm (3.40 eV). As shown in the spectrum, three emission peaks were observed in the violet–blue spectral range: 413 nm (3.00 eV), 437 nm (2.84 eV), and 462 nm (2.69 eV). A comparison of the direct band gap of Si3N4 (5.0–5.3 eV) shows that the three peaks clearly did not arise from the energy transition between the valence and conduction bands. They can be attributed to the trap-level defects in the materials. Normally, Si3N4 has a tetragonal structure where the Si atom is tetracoordinated by the N atoms, and the N atoms are tricoordinated by the Si atoms34. It has been widely accepted that four types of defects are present in Si3N4: Si–Si and N–N bonds, and Si and N dangling bonds32. Furthermore, a bonding σ orbital and an antibonding σ* orbital were formed by the Si–Si bond, and the energy gap was ~4.6 eV3637. The dangling bonds also led to energy level splitting. The Si dangling bonds form one defect state in the midgap between these two orbitals marked as N3 ≡ Si*3538. The other two N defective states are called N4+ and N2°, generating the levels within the gap. Moreover, an unclear X level found by Zhang et al. was close to the N3 ≡ Si* level39. Based on a previous study, the PL behavior of the Si3N4 nanobelts can be explained by the model. The emission at 3.00 eV can be attributed to the recombination between the Si–Si σ* level and the N2° level or between the N4+ level and the valence-band edge. The peak at 2.84 eV can be attributed to the recombination from the N2° level to the X level. Huang et al. also reported a similar emission peak at 2.87 eV; however, they assumed that the presence of oxygen, which introduced the N–Si–O defective state in the gap, caused the emission ~2.8 eV21. As shown in the PL spectrum, the contribution from the 2.69 eV peak is much lower than the others. Thus, the double-photon absorption excitation from the valence edge to N3 ≡ Si* and then to the conduction edge may lead to the emission39.

Bottom Line: The large-scale synthesis of Si3N4 nanobelts from quartz and graphite on a graphite-felt substrate was successfully achieved by catalyst-assisted carbothermal reduction-nitridation.The Fe(NO3)3 played a crucial role in promoting the nanobelt formation in the initial stage.The room-temperature photoluminescence spectrum of Si3N4 nanobelts consists of three emission peaks centered at 413, 437, and 462 nm, indicating potential applications in optoelectronic nanodevices.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Technology, Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, China University of Geosciences, Beijing, 100083.

ABSTRACT
The large-scale synthesis of Si3N4 nanobelts from quartz and graphite on a graphite-felt substrate was successfully achieved by catalyst-assisted carbothermal reduction-nitridation. The phase composition, morphology, and microstructure of Si3N4 nanobelts were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. The Si3N4 nanobelts were ~4-5 mm long and ~60 nm thick and exhibited smooth surfaces and flexible shapes. The Si3N4 nanobelts were well crystallized and grow along the [101] direction. The growth is dominated by the combined mechanisms of vapor-liquid-solid base growth and vapor-solid tip growth. The Fe(NO3)3 played a crucial role in promoting the nanobelt formation in the initial stage. The room-temperature photoluminescence spectrum of Si3N4 nanobelts consists of three emission peaks centered at 413, 437, and 462 nm, indicating potential applications in optoelectronic nanodevices.

No MeSH data available.