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Electrical, structural, and optical properties of sulfurized Sn-doped In2O 3 nanowires.

Zervos M, Mihailescu CN, Giapintzakis J, Othonos A, Travlos A, Luculescu CR - Nanoscale Res Lett (2015)

Bottom Line: We observe the existence of cubic bixbyite In2O3 and hexagonal SnS2 after processing the Sn:In2O3 nanowires to H2S at 300 °C but also cubic bixbyite In2O3, which remains dominant, and the emergence of rhombohedral In2(SO4)3 at 400 °C.The resultant nanowires maintain their metallic-like conductivity, and exhibit photoluminescence at 3.4 eV corresponding to band edge emission from In2O3.In contrast, Sn:In2O3 nanowires grown on glass at 500 °C can be treated under H2S only below 200 °C which is important for the fabrication of Cu2S/Sn:In2O3 core-shell p-n junctions on low-cost transparent substrates such as glass suitable for quantum dot-sensitized solar cells.

View Article: PubMed Central - PubMed

Affiliation: Nanostructured Materials and Devices Laboratory, Department of Mechanical and Manufacturing Engineering, P.O. Box 20537, Nicosia, 1678, Cyprus, zervos@ucy.ac.cy.

ABSTRACT
Sn-doped In2O3 nanowires have been grown on Si via the vapor-liquid-solid mechanism at 800 °C and then exposed to H2S between 300 to 600 °C. We observe the existence of cubic bixbyite In2O3 and hexagonal SnS2 after processing the Sn:In2O3 nanowires to H2S at 300 °C but also cubic bixbyite In2O3, which remains dominant, and the emergence of rhombohedral In2(SO4)3 at 400 °C. The resultant nanowires maintain their metallic-like conductivity, and exhibit photoluminescence at 3.4 eV corresponding to band edge emission from In2O3. In contrast, Sn:In2O3 nanowires grown on glass at 500 °C can be treated under H2S only below 200 °C which is important for the fabrication of Cu2S/Sn:In2O3 core-shell p-n junctions on low-cost transparent substrates such as glass suitable for quantum dot-sensitized solar cells.

No MeSH data available.


PL spectra of SnO2 (a), Sn:In2O3 (b), and SnS2:In2O3 (c) NWs obtained from Sn:In2O3 exposed to H2S at 300 °C for 60 min, taken at 300 K. Left inset shows the I–V characteristic of the Sn:In2O3 and SnS2:In2O3 NWs; right inset shows EDX spectrum of the Sn:In2O3 NWs processed at 400 °C
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Fig3: PL spectra of SnO2 (a), Sn:In2O3 (b), and SnS2:In2O3 (c) NWs obtained from Sn:In2O3 exposed to H2S at 300 °C for 60 min, taken at 300 K. Left inset shows the I–V characteristic of the Sn:In2O3 and SnS2:In2O3 NWs; right inset shows EDX spectrum of the Sn:In2O3 NWs processed at 400 °C

Mentions: Sn-doped In2O3 NWs were grown by the VLS mechanism on 1 nm Au/Si(001) at 800 °C using 1–5 % Sn [11]. A typical SEM image of the Sn-doped In2O3 NWs is shown in Fig. 1a. Their diameters varied between 50 to 100 nm as shown by the inset in Fig. 1a while their lengths reached up to 100 μm. We have shown previously that the Sn-doped In2O3 NWs have the cubic bixbyite crystal structure of In2O3 as confirmed by GIXD but also by high resolution transmission electron microscopy (HRTEM) analysis which showed that the lattice spacing is equal to 0.718 nm and corresponds to the d-spacing of the {−1,1,0} crystallographic planes of the cubic bixbyite crystal structure of In2O3 [11]. However, we also observed the formation of SnO2 nanoparticles with a tetragonal rutile crystal structure on the surface of the Sn-doped In2O3 NWs as shown by the inset of Fig. 1a which is attributed to the limited miscibility and different ionic radii of Sn and In. We do not observe the fluorite structure of InxSnyO3.5 as shown recently by Meng et al. [19] who observed a flux-induced crystal phase transition in the VLS growth of Sn-doped In2O3 NWs. The PL of the Sn-doped In2O3 NWs was found to be broad with a maximum at λ = 500 nm or 2.5 eV that shifts to 450 nm or ≈2.8 eV upon reducing the content of Sn to 1 % which also results into an increase in the carrier lifetime as shown previously by time-resolved PL [11]. The PL of the as-grown Sn-doped In2O3 NWs at 2.8 eV, which is shown in Fig. 3, is not related to band edge emission from In2O3, which is an n-type semiconductor with a direct energy band gap of 3.5 eV and a lower indirect gap of 2.6 eV. Instead, the PL at 2.8 eV is attributed to radiative recombination related to oxygen vacancies and states residing energetically in the upper half of the energy band gap of In2O3 as we have shown previously from ultrafast absorption-transmission spectroscopy. Furthermore the n-type Sn-doped In2O3 NWs had metallic-like conductivities and resistances up to 100 Ω determined from the linear I–V characteristics, shown as an inset in Fig. 3, due to the larger carrier densities of the order of 1019 to 1020 cm−3 [18].Fig. 1


Electrical, structural, and optical properties of sulfurized Sn-doped In2O 3 nanowires.

Zervos M, Mihailescu CN, Giapintzakis J, Othonos A, Travlos A, Luculescu CR - Nanoscale Res Lett (2015)

PL spectra of SnO2 (a), Sn:In2O3 (b), and SnS2:In2O3 (c) NWs obtained from Sn:In2O3 exposed to H2S at 300 °C for 60 min, taken at 300 K. Left inset shows the I–V characteristic of the Sn:In2O3 and SnS2:In2O3 NWs; right inset shows EDX spectrum of the Sn:In2O3 NWs processed at 400 °C
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Fig3: PL spectra of SnO2 (a), Sn:In2O3 (b), and SnS2:In2O3 (c) NWs obtained from Sn:In2O3 exposed to H2S at 300 °C for 60 min, taken at 300 K. Left inset shows the I–V characteristic of the Sn:In2O3 and SnS2:In2O3 NWs; right inset shows EDX spectrum of the Sn:In2O3 NWs processed at 400 °C
Mentions: Sn-doped In2O3 NWs were grown by the VLS mechanism on 1 nm Au/Si(001) at 800 °C using 1–5 % Sn [11]. A typical SEM image of the Sn-doped In2O3 NWs is shown in Fig. 1a. Their diameters varied between 50 to 100 nm as shown by the inset in Fig. 1a while their lengths reached up to 100 μm. We have shown previously that the Sn-doped In2O3 NWs have the cubic bixbyite crystal structure of In2O3 as confirmed by GIXD but also by high resolution transmission electron microscopy (HRTEM) analysis which showed that the lattice spacing is equal to 0.718 nm and corresponds to the d-spacing of the {−1,1,0} crystallographic planes of the cubic bixbyite crystal structure of In2O3 [11]. However, we also observed the formation of SnO2 nanoparticles with a tetragonal rutile crystal structure on the surface of the Sn-doped In2O3 NWs as shown by the inset of Fig. 1a which is attributed to the limited miscibility and different ionic radii of Sn and In. We do not observe the fluorite structure of InxSnyO3.5 as shown recently by Meng et al. [19] who observed a flux-induced crystal phase transition in the VLS growth of Sn-doped In2O3 NWs. The PL of the Sn-doped In2O3 NWs was found to be broad with a maximum at λ = 500 nm or 2.5 eV that shifts to 450 nm or ≈2.8 eV upon reducing the content of Sn to 1 % which also results into an increase in the carrier lifetime as shown previously by time-resolved PL [11]. The PL of the as-grown Sn-doped In2O3 NWs at 2.8 eV, which is shown in Fig. 3, is not related to band edge emission from In2O3, which is an n-type semiconductor with a direct energy band gap of 3.5 eV and a lower indirect gap of 2.6 eV. Instead, the PL at 2.8 eV is attributed to radiative recombination related to oxygen vacancies and states residing energetically in the upper half of the energy band gap of In2O3 as we have shown previously from ultrafast absorption-transmission spectroscopy. Furthermore the n-type Sn-doped In2O3 NWs had metallic-like conductivities and resistances up to 100 Ω determined from the linear I–V characteristics, shown as an inset in Fig. 3, due to the larger carrier densities of the order of 1019 to 1020 cm−3 [18].Fig. 1

Bottom Line: We observe the existence of cubic bixbyite In2O3 and hexagonal SnS2 after processing the Sn:In2O3 nanowires to H2S at 300 °C but also cubic bixbyite In2O3, which remains dominant, and the emergence of rhombohedral In2(SO4)3 at 400 °C.The resultant nanowires maintain their metallic-like conductivity, and exhibit photoluminescence at 3.4 eV corresponding to band edge emission from In2O3.In contrast, Sn:In2O3 nanowires grown on glass at 500 °C can be treated under H2S only below 200 °C which is important for the fabrication of Cu2S/Sn:In2O3 core-shell p-n junctions on low-cost transparent substrates such as glass suitable for quantum dot-sensitized solar cells.

View Article: PubMed Central - PubMed

Affiliation: Nanostructured Materials and Devices Laboratory, Department of Mechanical and Manufacturing Engineering, P.O. Box 20537, Nicosia, 1678, Cyprus, zervos@ucy.ac.cy.

ABSTRACT
Sn-doped In2O3 nanowires have been grown on Si via the vapor-liquid-solid mechanism at 800 °C and then exposed to H2S between 300 to 600 °C. We observe the existence of cubic bixbyite In2O3 and hexagonal SnS2 after processing the Sn:In2O3 nanowires to H2S at 300 °C but also cubic bixbyite In2O3, which remains dominant, and the emergence of rhombohedral In2(SO4)3 at 400 °C. The resultant nanowires maintain their metallic-like conductivity, and exhibit photoluminescence at 3.4 eV corresponding to band edge emission from In2O3. In contrast, Sn:In2O3 nanowires grown on glass at 500 °C can be treated under H2S only below 200 °C which is important for the fabrication of Cu2S/Sn:In2O3 core-shell p-n junctions on low-cost transparent substrates such as glass suitable for quantum dot-sensitized solar cells.

No MeSH data available.