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Long-term oxidization and phase transition of InN nanotextures.

Sarantopoulou E, Kollia Z, Dražic G, Kobe S, Antonakakis NS - Nanoscale Res Lett (2011)

Bottom Line: The long-term (6 months) oxidization of hcp-InN (wurtzite, InN-w) nanostructures (crystalline/amorphous) synthesized on Si [100] substrates is analyzed.The densely packed layers of InN-w nanostructures (5-40 nm) are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-Ox-Ny (indium oxynitride) phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture.When the oxidized area exceeds the critical size of 5 nm, the amorphous In-Ox-Ny phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vassileos Constantinou Avenue, Athens 11635, Greece. esarant@eie.gr.

ABSTRACT
The long-term (6 months) oxidization of hcp-InN (wurtzite, InN-w) nanostructures (crystalline/amorphous) synthesized on Si [100] substrates is analyzed. The densely packed layers of InN-w nanostructures (5-40 nm) are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-Ox-Ny (indium oxynitride) phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture. High-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy and selected area electron diffraction are used to identify amorphous In-Ox-Ny oxynitride phase. When the oxidized area exceeds the critical size of 5 nm, the amorphous In-Ox-Ny phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase.

No MeSH data available.


TEM image and EDXS of InN surface following electron beam impact. (a) TEM image of the destroyed nanocrystalline domains deposited on Ni grids after electron irradiation. (b) EDXS of the e-beam-irradiated crystal nanodomains. Only the indium peak is observed. (c) Indium nanocrystal sphere of tetragonal structure formed after e-beam irradiation. (d) SAED of the nanosphere with the tetragonal crystalline structure of pure indium.
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Figure 4: TEM image and EDXS of InN surface following electron beam impact. (a) TEM image of the destroyed nanocrystalline domains deposited on Ni grids after electron irradiation. (b) EDXS of the e-beam-irradiated crystal nanodomains. Only the indium peak is observed. (c) Indium nanocrystal sphere of tetragonal structure formed after e-beam irradiation. (d) SAED of the nanosphere with the tetragonal crystalline structure of pure indium.

Mentions: The capturing of HRTEM images of InN crystals is not a trivial issue because InN is unstable under electron irradiation [32], due to its low dissociation energy (0.073 eV) [33]. The InN crystals first are transferred to a lacey-carbon-coated Ni grid using a scalpel knife, and then they are transferred to the carbon-coated TEM grid. The samples are examined under mild electron beam conditions; current density of the order of 10-5 nA/nm2, 50-μm condenser aperture, and spot size 3. With this method, although the information of relative orientation between the InN and Si substrate is lost, there are no artifacts such as structure alteration related to ion-milling. In addition, ion-milling is not recommended because InN is thermally dissociated. The electron beam destroys the InN structure by changing the morphology of the dendrite structures, and new aggregations of 20-40 nm nanospheres distributed selectively around the periphery of the grid cells are formed (Figure 4a). The change of the film morphology is accompanied by structural changes and the EDXS of the areas exposed to e-beam and a deficiency in nitrogen (Figure 4b). This is additionally confirmed by SAED, and the image of one indium nanosphere (Figure 4c) reveals the tetragonal crystal structure of pure indium (Figure 4d). In addition, no traces of oxygen are identified.


Long-term oxidization and phase transition of InN nanotextures.

Sarantopoulou E, Kollia Z, Dražic G, Kobe S, Antonakakis NS - Nanoscale Res Lett (2011)

TEM image and EDXS of InN surface following electron beam impact. (a) TEM image of the destroyed nanocrystalline domains deposited on Ni grids after electron irradiation. (b) EDXS of the e-beam-irradiated crystal nanodomains. Only the indium peak is observed. (c) Indium nanocrystal sphere of tetragonal structure formed after e-beam irradiation. (d) SAED of the nanosphere with the tetragonal crystalline structure of pure indium.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211480&req=5

Figure 4: TEM image and EDXS of InN surface following electron beam impact. (a) TEM image of the destroyed nanocrystalline domains deposited on Ni grids after electron irradiation. (b) EDXS of the e-beam-irradiated crystal nanodomains. Only the indium peak is observed. (c) Indium nanocrystal sphere of tetragonal structure formed after e-beam irradiation. (d) SAED of the nanosphere with the tetragonal crystalline structure of pure indium.
Mentions: The capturing of HRTEM images of InN crystals is not a trivial issue because InN is unstable under electron irradiation [32], due to its low dissociation energy (0.073 eV) [33]. The InN crystals first are transferred to a lacey-carbon-coated Ni grid using a scalpel knife, and then they are transferred to the carbon-coated TEM grid. The samples are examined under mild electron beam conditions; current density of the order of 10-5 nA/nm2, 50-μm condenser aperture, and spot size 3. With this method, although the information of relative orientation between the InN and Si substrate is lost, there are no artifacts such as structure alteration related to ion-milling. In addition, ion-milling is not recommended because InN is thermally dissociated. The electron beam destroys the InN structure by changing the morphology of the dendrite structures, and new aggregations of 20-40 nm nanospheres distributed selectively around the periphery of the grid cells are formed (Figure 4a). The change of the film morphology is accompanied by structural changes and the EDXS of the areas exposed to e-beam and a deficiency in nitrogen (Figure 4b). This is additionally confirmed by SAED, and the image of one indium nanosphere (Figure 4c) reveals the tetragonal crystal structure of pure indium (Figure 4d). In addition, no traces of oxygen are identified.

Bottom Line: The long-term (6 months) oxidization of hcp-InN (wurtzite, InN-w) nanostructures (crystalline/amorphous) synthesized on Si [100] substrates is analyzed.The densely packed layers of InN-w nanostructures (5-40 nm) are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-Ox-Ny (indium oxynitride) phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture.When the oxidized area exceeds the critical size of 5 nm, the amorphous In-Ox-Ny phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vassileos Constantinou Avenue, Athens 11635, Greece. esarant@eie.gr.

ABSTRACT
The long-term (6 months) oxidization of hcp-InN (wurtzite, InN-w) nanostructures (crystalline/amorphous) synthesized on Si [100] substrates is analyzed. The densely packed layers of InN-w nanostructures (5-40 nm) are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-Ox-Ny (indium oxynitride) phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture. High-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy and selected area electron diffraction are used to identify amorphous In-Ox-Ny oxynitride phase. When the oxidized area exceeds the critical size of 5 nm, the amorphous In-Ox-Ny phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase.

No MeSH data available.