Hybrid Graphene and Carbon Nanotube Thin Films

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Transcript of Hybrid Graphene and Carbon Nanotube Thin Films

Slide 1

Hybrid Graphene and Carbon Nanotube Thin Films: Theres Node Way OutJohn Sandford ONeillMSci Presentation

17/03/2015

1

ITO and Transparent ElectrodesTransparent electrodes are a key part of display devices and touchscreens

Dominant material is Indium Tin Oxide (ITO)High conductivity (20 /sq sheet resistance)High transparency (~90%)Price fluctuations due to indium scarcityBrittle and easily cracked

Image: Planet AnalogGraph: US Geological Survey

Carbon NanomaterialsAllotropes of carbon with extraordinary propertiesHigh electron mobilityMechanical StrengthOptical TransparencyPotential applications(Flexible) display devicesCapacitorsComposite materialsMicroprocessor architecturesLiquid-phase processing Industrially scalable

Images: Bae, Sukang, et al. Nature nano, 5.8, 574-578.

Synthesis of Single-Walled Carbon Nanotubes (SWNTs)Intercalation of bundled carbon nanotubes with sodium metal ammonia solution

Image credit: The Linde Group

Dissolution of nanotubide salt in DMF organic polar solvent

Synthesis of Single-Walled Carbon Nanotubes (SWNTs)

Intercalation of bundled carbon nanotubes with sodium metal ammonia solution

Dissolution of nanotubide salt in DMF organic polar solvent

Synthesis of Graphene

Graphite intercalated with potassium-ammonia solution to yield KC24(NH3)4 graphite intercalation compound (GIC)GIC dissolved in THF solventSolvated graphene sheet (graphenide)

Thin Film FabricationDeposition methods: drop coating, spin coatingInert atmosphereSolvent evaporates leaving immobilised nanocarbons on substrateMulti-layered films made by allowing each layer to dry before deposition of next layerSubstrateDeposition Layer 1Deposition Layer 2

Carbon Nanotube Thin Films

MicaCNT

0.1 mg/ml SWNTs in DMF drop coated onto mica substrate

Cross-section indicates a mixture of individualised SWNT and small tube bundles

Carbon Nanotube Thin Films

MicaCNT0.01 mg/ml SWNTs in DMF drop coated onto mica substrateCross-section indicates a mixture of individualised SWNT and small tube bundles

Graphene Thin Films

MicaGIC0.1 mg/ml GIC in THF drop coated onto mica substrate

Cross-section shows graphene platelets ~1 nm in height and ~300nm diameter (same as starting graphite material)

Hybrid Thin Films

MicaGICCNT

0.1 mg/ml GIC in THF followed by 0.1 mg/ml SWNT in DMF drop coated onto mica substrateExperimented with concentration and order of graphene/SWNT layers

ConductivitySheet resistance of thin films measured with 4-point probe

ProbesThin Film SampleThin Film Sample Sheet ResistanceITO sample20.4 /sqGraphene Carbon Nanotubes51.64 k/sq1st layer: Graphene 2nd layer: Carbon Nanotubes15.76 k/sq1st layer: Carbon Nanotubes 2nd layer: Graphene80.63 k/sq

Hybrid filmsDepositing graphene below the CNTs resulted in lower resistances than graphene above the CNTs, or films consisting only of CNTs

Carbon Nanotube Network Nodes

Carbon Nanotube Film51.64 k/sq

Hybrid Film15.76 k/sq

MicaCNTMicaGICCNT

Optimisation of Graphene ConcentrationMicaGICCNTThin films had 1st layer of graphene of varying concentration then 0.1 mg/ml CNT in DMFSuperior FOM for all hybrid filmsBest performance around 0.05 mg/ml graphene concentration

ConclusionsThe metal-ammonia intercalation method was successfully used to exfoliate carbon nanomaterials Graphene and single-walled carbon nanotubes were individualised in solutionHybrid thin films were shown to have superior electrical and optical properties to single-component films

Future WorkPost-deposition treatments: washing, annealingOptimisation of CNT concentrationCharacterisation with Raman SpectroscopyDetailed analysis of deposition techniquesDifferent substrates glassDifferent solvents NMP, DMSO

AcknowledgementsNeal SkipperChris HowardPaddy CullenDave BuckleyLuca SantarelliKashim Bin SubhanKathy CoxRichard Thorogate

Any [email protected]

Characterisation of KC24(NH3)4 GIC: Powder X-Ray Diffraction

Stage 1Stage 2Stage 33.356.376.506.61Mainly stage 2 and stage 3 GIC graphene bilayers and trilayers

Characterisation of KC24(NH3)4 GIC: UV-Vis Spectroscopy270nm absorption peak corresponding to interband transitions of graphene in solution

Characterisation of SWNT Solution: UV-Vis Spectroscopy270nm absorption peak corresponding to plasmon resonance

Post-Deposition Thin Film Treatment