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High-Performance Stable Field Emission with Ultralow Turn on Voltage from rGO Conformal Coated TiO2 Nanotubes 3D Arrays.

Agrawal Y, Kedawat G, Kumar P, Dwivedi J, Singh VN, Gupta RK, Gupta BK - Sci Rep (2015)

Bottom Line: A facile method to produce conformal coated reduced graphene oxide (rGO) on vertically aligned titanium oxide (TiO2) nanotubes three dimensional (3D) arrays (NTAs) is demonstrated for enhanced field emission display applications.Moreover, these enhancements observed in nano arrays attribute to the contribution of low work function with non-rectifying barriers, which allow an easy injection of electrons from the conduction band of TiO2 into the Fermi level of reduced graphene oxide under external electric field.The obtained results are extremely advantageous for its potential application in field emission devices.

View Article: PubMed Central - PubMed

Affiliation: CSIR - National Physical Laboratory, Dr K S Krishnan Road, New Delhi, 110012, India.

ABSTRACT
A facile method to produce conformal coated reduced graphene oxide (rGO) on vertically aligned titanium oxide (TiO2) nanotubes three dimensional (3D) arrays (NTAs) is demonstrated for enhanced field emission display applications. These engineered nano arrays exhibit efficient electron field emission properties such as high field emission current density (80 mA/cm(2)), low turn-on field (1.0 V/μm) and field enhancement factor (6000) with high emission current stability. Moreover, these enhancements observed in nano arrays attribute to the contribution of low work function with non-rectifying barriers, which allow an easy injection of electrons from the conduction band of TiO2 into the Fermi level of reduced graphene oxide under external electric field. The obtained results are extremely advantageous for its potential application in field emission devices.

No MeSH data available.


Field emission characteristics of typical field emission devices based onrGO-TiO2 NTAs hybrid nanostructures(a) Field emission characteristics of different field emission devices(conformal coated rGO on annealed TiO2 NTAs hybrid structure,annealed TiO2 NTAs, as-synthesized TiO2 NTAs,rGO-commercial TiO2 NPs, commercial TiO2 NPs, rGO-Tisheet, rGO and Ti sheet samples), (b) stability of field emissioncurrents from a typical field emission device (conformal coated rGO onannealed TiO2 NTAs hybrid structure) at 230 voltages and(c) Fowler-Nordheim characteristics curves for different fieldemission devices (conformal coated rGO on annealed TiO2 NTAs,annealed TiO2 NTAs, as-synthesized TiO2 NTAs andcommercial TiO2 NPs).
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f4: Field emission characteristics of typical field emission devices based onrGO-TiO2 NTAs hybrid nanostructures(a) Field emission characteristics of different field emission devices(conformal coated rGO on annealed TiO2 NTAs hybrid structure,annealed TiO2 NTAs, as-synthesized TiO2 NTAs,rGO-commercial TiO2 NPs, commercial TiO2 NPs, rGO-Tisheet, rGO and Ti sheet samples), (b) stability of field emissioncurrents from a typical field emission device (conformal coated rGO onannealed TiO2 NTAs hybrid structure) at 230 voltages and(c) Fowler-Nordheim characteristics curves for different fieldemission devices (conformal coated rGO on annealed TiO2 NTAs,annealed TiO2 NTAs, as-synthesized TiO2 NTAs andcommercial TiO2 NPs).

Mentions: The electron field emission involves extraction of electrons from the NTAs by quantumtunneling through the surface potential barrier46. The field emissioncharacteristics (field emission current density (J) as a function of appliedelectric field (E)) at a sample to cathode distance of100 μm for conformal coated rGO on annealed TiO2NTAs hybrid structure, annealed TiO2 NTAs, as-synthesized TiO2NTAs, rGO-commercial TiO2 NPs, commercial TiO2 NPs, rGO-Tisheet, rGO and Ti sheet samples are shown in Fig. 4(a). It isfound that the emission current density exponentially increases with increase in theapplied field for all the samples. An emission current density of 80mA/cm2 at 230 V is obtained for conformal coated rGOon annealed TiO2 NTAs sample, which is the highest value compared to theother rGO-commercial TiO2 NPs, commercial TiO2 nanoparticles(NPs), as-synthesized TiO2 NTAs, annealed TiO2 NTAs samples,pure Ti sheet, rGO nanosheets and rGO on pure Ti sheet substrate samples. Theobtained results suggest that rGO conformal coated on TiO2 NTAs hybridstructure is ultimate choice for better field emission characteristics. It may bedue to the presence of large no. of delocalized π electrons on thesurface of rGO which act as electron injection carriers3334. Fieldemission current also depends on the aspect ratio of the TiO2 nanotubes,which is very high in the present case. The field emission characteristics ofconformal coated rGO on annealed TiO2 NTAs, annealed TiO2NTAs, as-synthesized TiO2 NTAs and commercial TiO2 NPs samplesare shown in Figure S10a (see Supplementary Information). It can benoticed that the turn-on field (Eto) for conformal coated rGO on annealedTiO2 NTAs, annealed TiO2 NTAs, as-synthesizedTiO2 NTAs and commercial TiO2 NPs are 1.0, 1.4, 3.7 and4.8 V/μm, respectively (from Fig. 4aand S10a). The turn-on fieldEto values follows the sequences Eto (conformal coated rGOon annealed TiO2 NTAs) < Eto (annealed TiO2NTAs) < Eto (as-synthesized TiO2 NTAs) <Eto (commercial TiO2 NPs). Furthermore, the field emissioncharacteristics of different as-synthesized samples of conformal coated rGO onannealed TiO2 NTAs (sample 1, sample 2, sample 3 and sample 4) are alsoexamined to explore reproducibility and the results are shown in Figure S10b (see Supplementary Information). It can be noticed thatall the samples show similar and consistent behaviour. In addition to the above, thefield emission behaviour of rGO, rGO-Ti sheet, rGO-commercial TiO2nanoparticles and conformal coated rGO on annealed TiO2 NTAs samples from1st to 4th cycle run are shown in the Figure S11a-d (see Supplementary Information). All tested samplesshow better emission uniformity and a good reproducibility of field emissionbehaviour during the initial 4 cycle run. The conformal coated rGO on annealedTiO2 NTAs clearly demonstrate the higher current density at lowturn-on field (80 mA/cm2,1.0 V/μm) in compared to all other samples (annealedTiO2 NTAs, as-synthesized TiO2 NTAs, rGO-commercialTiO2 NPs, commercial TiO2 NPs, rGO-Ti sheet, rGO and Tisheet; Fig. 4a). The stability of emission current is alsoevaluated at 230 V for conformal coated rGO on annealed TiO2NTAs, as shown in Fig. 4b and it is found to be very stableand no significant change is observed over a time period of 120 min at a currentdensity 80 mA/cm2. Thus, the conformal coated rGO onannealed TiO2 NTAs shows a good electrical contact between theTiO2 nanotubes and rGO as well as it provides a long term stabilityof field emission currents.


High-Performance Stable Field Emission with Ultralow Turn on Voltage from rGO Conformal Coated TiO2 Nanotubes 3D Arrays.

Agrawal Y, Kedawat G, Kumar P, Dwivedi J, Singh VN, Gupta RK, Gupta BK - Sci Rep (2015)

Field emission characteristics of typical field emission devices based onrGO-TiO2 NTAs hybrid nanostructures(a) Field emission characteristics of different field emission devices(conformal coated rGO on annealed TiO2 NTAs hybrid structure,annealed TiO2 NTAs, as-synthesized TiO2 NTAs,rGO-commercial TiO2 NPs, commercial TiO2 NPs, rGO-Tisheet, rGO and Ti sheet samples), (b) stability of field emissioncurrents from a typical field emission device (conformal coated rGO onannealed TiO2 NTAs hybrid structure) at 230 voltages and(c) Fowler-Nordheim characteristics curves for different fieldemission devices (conformal coated rGO on annealed TiO2 NTAs,annealed TiO2 NTAs, as-synthesized TiO2 NTAs andcommercial TiO2 NPs).
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Related In: Results  -  Collection

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f4: Field emission characteristics of typical field emission devices based onrGO-TiO2 NTAs hybrid nanostructures(a) Field emission characteristics of different field emission devices(conformal coated rGO on annealed TiO2 NTAs hybrid structure,annealed TiO2 NTAs, as-synthesized TiO2 NTAs,rGO-commercial TiO2 NPs, commercial TiO2 NPs, rGO-Tisheet, rGO and Ti sheet samples), (b) stability of field emissioncurrents from a typical field emission device (conformal coated rGO onannealed TiO2 NTAs hybrid structure) at 230 voltages and(c) Fowler-Nordheim characteristics curves for different fieldemission devices (conformal coated rGO on annealed TiO2 NTAs,annealed TiO2 NTAs, as-synthesized TiO2 NTAs andcommercial TiO2 NPs).
Mentions: The electron field emission involves extraction of electrons from the NTAs by quantumtunneling through the surface potential barrier46. The field emissioncharacteristics (field emission current density (J) as a function of appliedelectric field (E)) at a sample to cathode distance of100 μm for conformal coated rGO on annealed TiO2NTAs hybrid structure, annealed TiO2 NTAs, as-synthesized TiO2NTAs, rGO-commercial TiO2 NPs, commercial TiO2 NPs, rGO-Tisheet, rGO and Ti sheet samples are shown in Fig. 4(a). It isfound that the emission current density exponentially increases with increase in theapplied field for all the samples. An emission current density of 80mA/cm2 at 230 V is obtained for conformal coated rGOon annealed TiO2 NTAs sample, which is the highest value compared to theother rGO-commercial TiO2 NPs, commercial TiO2 nanoparticles(NPs), as-synthesized TiO2 NTAs, annealed TiO2 NTAs samples,pure Ti sheet, rGO nanosheets and rGO on pure Ti sheet substrate samples. Theobtained results suggest that rGO conformal coated on TiO2 NTAs hybridstructure is ultimate choice for better field emission characteristics. It may bedue to the presence of large no. of delocalized π electrons on thesurface of rGO which act as electron injection carriers3334. Fieldemission current also depends on the aspect ratio of the TiO2 nanotubes,which is very high in the present case. The field emission characteristics ofconformal coated rGO on annealed TiO2 NTAs, annealed TiO2NTAs, as-synthesized TiO2 NTAs and commercial TiO2 NPs samplesare shown in Figure S10a (see Supplementary Information). It can benoticed that the turn-on field (Eto) for conformal coated rGO on annealedTiO2 NTAs, annealed TiO2 NTAs, as-synthesizedTiO2 NTAs and commercial TiO2 NPs are 1.0, 1.4, 3.7 and4.8 V/μm, respectively (from Fig. 4aand S10a). The turn-on fieldEto values follows the sequences Eto (conformal coated rGOon annealed TiO2 NTAs) < Eto (annealed TiO2NTAs) < Eto (as-synthesized TiO2 NTAs) <Eto (commercial TiO2 NPs). Furthermore, the field emissioncharacteristics of different as-synthesized samples of conformal coated rGO onannealed TiO2 NTAs (sample 1, sample 2, sample 3 and sample 4) are alsoexamined to explore reproducibility and the results are shown in Figure S10b (see Supplementary Information). It can be noticed thatall the samples show similar and consistent behaviour. In addition to the above, thefield emission behaviour of rGO, rGO-Ti sheet, rGO-commercial TiO2nanoparticles and conformal coated rGO on annealed TiO2 NTAs samples from1st to 4th cycle run are shown in the Figure S11a-d (see Supplementary Information). All tested samplesshow better emission uniformity and a good reproducibility of field emissionbehaviour during the initial 4 cycle run. The conformal coated rGO on annealedTiO2 NTAs clearly demonstrate the higher current density at lowturn-on field (80 mA/cm2,1.0 V/μm) in compared to all other samples (annealedTiO2 NTAs, as-synthesized TiO2 NTAs, rGO-commercialTiO2 NPs, commercial TiO2 NPs, rGO-Ti sheet, rGO and Tisheet; Fig. 4a). The stability of emission current is alsoevaluated at 230 V for conformal coated rGO on annealed TiO2NTAs, as shown in Fig. 4b and it is found to be very stableand no significant change is observed over a time period of 120 min at a currentdensity 80 mA/cm2. Thus, the conformal coated rGO onannealed TiO2 NTAs shows a good electrical contact between theTiO2 nanotubes and rGO as well as it provides a long term stabilityof field emission currents.

Bottom Line: A facile method to produce conformal coated reduced graphene oxide (rGO) on vertically aligned titanium oxide (TiO2) nanotubes three dimensional (3D) arrays (NTAs) is demonstrated for enhanced field emission display applications.Moreover, these enhancements observed in nano arrays attribute to the contribution of low work function with non-rectifying barriers, which allow an easy injection of electrons from the conduction band of TiO2 into the Fermi level of reduced graphene oxide under external electric field.The obtained results are extremely advantageous for its potential application in field emission devices.

View Article: PubMed Central - PubMed

Affiliation: CSIR - National Physical Laboratory, Dr K S Krishnan Road, New Delhi, 110012, India.

ABSTRACT
A facile method to produce conformal coated reduced graphene oxide (rGO) on vertically aligned titanium oxide (TiO2) nanotubes three dimensional (3D) arrays (NTAs) is demonstrated for enhanced field emission display applications. These engineered nano arrays exhibit efficient electron field emission properties such as high field emission current density (80 mA/cm(2)), low turn-on field (1.0 V/μm) and field enhancement factor (6000) with high emission current stability. Moreover, these enhancements observed in nano arrays attribute to the contribution of low work function with non-rectifying barriers, which allow an easy injection of electrons from the conduction band of TiO2 into the Fermi level of reduced graphene oxide under external electric field. The obtained results are extremely advantageous for its potential application in field emission devices.

No MeSH data available.