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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.


EELS spectra of nanostructures. (a) EELS spectra of large nanostructures where only oxygen is present. (b) EELS spectra of small nanostructures, where both oxygen and nitrogen are present.
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Figure 8: EELS spectra of nanostructures. (a) EELS spectra of large nanostructures where only oxygen is present. (b) EELS spectra of small nanostructures, where both oxygen and nitrogen are present.

Mentions: In addition, the elemental analysis with EDXS depends on the film morphology, and therefore EELS elemental analysis is used on small (<5 nm), and larger crystal and amorphous domains. The average concentration of elements (mol%) of the small-sized domains with EELS is 40% In, 40% O, and 20% N, respectively (Figure 8a, b). No traces of nitrogen are detected on large-sized domains as can be seen in Figure 6b. These results imply that oxidization starts by forming a small nucleus of the oxidized areas in the InN nanodomains with dimensions less than 5 nm. Taking into consideration that the surface of InN films is highly porous, the atmospheric oxygen diffuses first into the InN grid and then slowly oxidizes InN to an amorphous In-Ox-Ny phase (Figure 6a, C). The amorphous phase eventually undergoes a second-order phase transition to a crystal line In2O3 phase, when the size of the oxidized areas exceeds the critical value of approx. 5 nm. The results of EELS and HRTEM suggest that the chemical reaction is accompanied by agglomeration of small-sized oxidized domains, forming larger crystal domains of indium oxide only.


Long-term oxidization and phase transition of InN nanotextures.

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

EELS spectra of nanostructures. (a) EELS spectra of large nanostructures where only oxygen is present. (b) EELS spectra of small nanostructures, where both oxygen and nitrogen are present.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 8: EELS spectra of nanostructures. (a) EELS spectra of large nanostructures where only oxygen is present. (b) EELS spectra of small nanostructures, where both oxygen and nitrogen are present.
Mentions: In addition, the elemental analysis with EDXS depends on the film morphology, and therefore EELS elemental analysis is used on small (<5 nm), and larger crystal and amorphous domains. The average concentration of elements (mol%) of the small-sized domains with EELS is 40% In, 40% O, and 20% N, respectively (Figure 8a, b). No traces of nitrogen are detected on large-sized domains as can be seen in Figure 6b. These results imply that oxidization starts by forming a small nucleus of the oxidized areas in the InN nanodomains with dimensions less than 5 nm. Taking into consideration that the surface of InN films is highly porous, the atmospheric oxygen diffuses first into the InN grid and then slowly oxidizes InN to an amorphous In-Ox-Ny phase (Figure 6a, C). The amorphous phase eventually undergoes a second-order phase transition to a crystal line In2O3 phase, when the size of the oxidized areas exceeds the critical value of approx. 5 nm. The results of EELS and HRTEM suggest that the chemical reaction is accompanied by agglomeration of small-sized oxidized domains, forming larger crystal domains of indium oxide only.

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.