Efficient Fabrication of Stable Graphene‐Molecule‐Graphene ...
Graphene - web.stanford.eduweb.stanford.edu/~sidaw/projects/graphene.pdfPotential Applications...
Transcript of Graphene - web.stanford.eduweb.stanford.edu/~sidaw/projects/graphene.pdfPotential Applications...
Graphene
Sida Wang
Overview
• Overview– Current Research– Current Research
– Potential Application
• My Work– Theoretical
– Experimental
– Patterns
Graphene: Overview of Properties
• Graphene has many impressive properties
– It is not supposed to exist (Landau and Peierls)
– zero-gap semiconductor
– Its charge carriers mimic relativistic particles– Its charge carriers mimic relativistic particles
– Ballistic electrons
– Non-diminishing conductivity
– Room temperature quantum hall effect
Stabilization Mechanism
• Small deformation in the third dimension
Potential Applications
� Graphene based electronics
� Battery (High surface to volume ratio)
� Light weight micromechanical resonator
� Sensitive chemical detector� Sensitive chemical detector
� Molecular Sieves
My Work: Making Graphene
• Background
• Experimental Work
• The goal: observe photocurrent in • The goal: observe photocurrent in graphene as predicted by E. J. Mele, Petr Kra´l, David Toma´nek
Methods
• Micromechanical Exfoliation
• Chemical Synthesis (222 carbons)
• Decomposition of SiC wafer
• Reduction of graphene oxide
Pealing with tape
• Reduction of graphene oxide
• Other Sophisticated Methods
Detection Methods
• AFM is the only direct detection method
– Limited by scanning range, and speed
• Optical detection was crucial to the discovery of graphenediscovery of graphene
Optical Contrast
• The thickness of graphene is ~0.3 nm
• Transparent in air
• The contrast is high only for specific substrates (300nm of SiO on Si)substrates (300nm of SiO2 on Si)
• P. Blake et al, Making graphene visible
The Problem
Contrast = (R2 – R1)/R1
graphene
R2R1
SiO2
Si
graphene
The Abstract Problem
The Simpler Problem
The Solution
ResultsPlot of Contrast
Wavelength (nm)
Contrast = (R2 – R1)/R1
Designing New Substrate
• A good substrate with higher contrast must be possible.
More Contrast
• Changing n of the substrate(n0=5.4-0.4i)
n=2.2-0.4i
More Contrast
• By changing n of the thinfilm (n0=1.41)
n=2.3
Experimental Work
• There is a 10% contrast
• But there are other troubles experimentallyA
Experimental Concerns
• The probability distribution number of layers
Another Unhelpful Distribution
• The probability distribution area
A Beneficial Distribution
• Probability of spotting the sample in 1 sec
Mostly random but certain things help
• Parameters
– Pressure (strength and time and what type)
– Number of cleave
– Surface treatment of wafer– Surface treatment of wafer
– Other details
My Samples
Analysis
Intensity Analysis
Intensity vs. Position
Errors In Intensity Analysis
Some Patterns
• Patterns are interesting
On the graphite
59 degrees
60 degrees
SEM Image of Graphene
A. K. GEIM, K. S. NOVOSELOV, Rise of graphene, Nature
Graphene Industries and UBC Samples
Graphene industries UBC
Folding
The graphite
Angles and Straight Edges
120 degrees
118 degrees117 degrees
118 degrees
120 degrees122 degrees
30 microns
Upper Limit in Size
Current Price of Graphene
• Graphene Industries sold a 900µm2 piece for £400 = $820
• $ 1,227,000,000,000,000 per gram
– Lasts 3 million years at a rate of spending of 1 – Lasts 3 million years at a rate of spending of 1 million dollars a day
– 36m x 36m =1300m2 in area
Future Works
• More and larger samples
• Reliably characterizing the samples
• Shoot the samples with a laser
• Placing electrodes on the samples• Placing electrodes on the samples
Summary
• Current Research
– Properties and potential applications of graphene
• My Work• My Work
– Theoretical, multilayer reflection problem
– Experimental, making samples
– Patterns on the samples
I sincerely thank
• Prof. van Driel for this opportunity
• Everyone for being very nice and very helpful
• Ryan for patiently explaining a lot of things• Ryan for patiently explaining a lot of things
• Thank you!
Extra Slides
Stronger than modelled
• Heats of hydrogenation
– 29 kilocalories
3x29=87 > 50
– 50 kilocalories
Features of Contrast Function
• The contrast between n layer and n+1 layers remains approximately constant when n is small. And approaches 0 when n is large.n is large.
• High contrast at low reflectivity
• Linear