Graphene

1. Graphene A modern material with unique physical and electrical properties that could reshape our future. By: Steven Douglas 4/24/15

2. Outline: • Introduction to graphene. • History. • Physical properties. • Electrical properties. • Other properties. • How graphene is created. • Graphene’s current uses. • Batteries • Capacitors • Transistors • Graphene’s future. • Challenges surrounding graphene. • Summary/Conclusion • Key concepts. • References.

3. Introduction to Graphene • The first 2-dimensional material ever discovered. • One-atom thick of carbon atoms arranged in a hexagonal lattice. • Found in graphite, coal, and created in other fashions. • Hard to manufacture in large quantities, just about all graphene produced is used for R&D within companies and universities. • The strongest, lightest, and most conductive material known to man.

4. Graphene’s short history: • Discovered by Andre Geim and Konstantin Novoselov in 2004, however this is apparently debatable. • First conceived in 1946. But they didn’t believe it could be created at room temperature. • Graphene as we know it was theoretically mentioned as recent as 1984 to describe the layers of graphite. • The term “Graphene” was used mainly In working with Carbon Nano-tubes.

5. Amazing Physical Properties: • The strongest material ever measured. Up to 150X stronger than the equivalent weight of steel. • Pliable as rubber and has the ability to stretch up to 120% of its length then recover its original shape. • Extremely light weight, its said that a single sheet of Graphene covering a whole football field would weigh less than 1g.

6. Electrical Properties • Graphene is classified as a zero-overlap semi-metal, which means that either holes or electrons are charge carriers. • Very high electrical conductivity when exposed to an electric field. • In a vacuum, it had a mobility that was up to 250X that of Si. Out conducts copper by a thousand times. • Effective mass at the Dirac point is zero for both electrons and holes.

7. Other Properties: • Only known substance that is completely impermeable to gas. • Graphene oxide reportedly has the ability to attract radioactive material. • Safer creation of “Quantum Dots”. Reduces the price from $1million a kg to $100 a ton. • Also has some optical properties that are being tested as we speak. • Graphene has the ability to transmit up to 98% of light.

8. How graphene is created:Mechanical Exfoliation • Typically involves scotch tape. • Stick the tape to a graphite block. • Use another piece of tape and stick the two sticky sides together. Repeat this process 20-100x • Press the piece of tape with the graphene on a substrate.

9. Chemical exfoliation • The block graphite is submerged into a solvent. • An ultrasound is used to cause a splitting effect within the graphite structure. • Prolonged exposure causes little platelets to be formed. • Enriched by a centrifuge.

10. CE via graphene oxide • Uses the same process as chemical exfoliation but graphene is oxidized. • After the CE process, it is then deposited on substrate and reduced to parent graphene in some fashion.

11. Chemical Vapour Deposition • The most common practice in creating graphene today. • Typically a copper substrate is exposed to a low pressure, 1000˚C annealing process. • Methane and Hydrogen gas flows through the furnace. • Carbon atoms from Methane deposite on the copper, creating a continuous graphene sheet.

12. Silicon Carbide • A small amount of silicon carbide is placed in a box with a hole in it. • The box is sealed in a vacuum or argon gas and heated to 1500˚C. • Si molecules evaporate from the surface leaving a layer of graphene.

13. Graphene’s current uses: • In early 2014 I.B.M announced that it had built the first integrated circuit for wireless devices. • Today a tennis racquet with a graphene layer has been manufactured. • Graphene is an ingredient to conductive inks for printing circuitry. • Samsung is reportedly releasing a screen that employs Graphene to deliver current to the display.

14. Optical Electronics • Believed to mainly be used in touchscreens, OLED, and LCD. • Graphene matches Indium-Tin Oxide performance in its basic state.

15. Energy storage • Graphene is being experimented in both supercapacitor and battery construction.

16. Energy storage cont. • Graphene based supercapacitors have potential to replace small batteries. • Uses the chemical exfoliation discussed earlier. • Was able to light LED’s with a two minute charge for around twelve hours.

17. Graphene & Transistors • Clocked at 427 Ghz. • Create a false band gap by employing “Negative” resistance. • Another type of FET uses dual gate construction.

18. Graphene’s future • Biomedical Engineering • Optical Electronics • Ultra-Filtration • Composite Materials • Photo-Voltaic cells • Energy Storage • Radioactive Clean-up

19. Challenges Surrounding Graphene • Graphene has no bandwidth, which means it cannot be shut off. • A very hydrophobic material • Very expensive and hard to manufacture for most companies. • When deployed it seemed that the results weren’t duplicated. • Graphene is hard to produce in large usable sheets. Small flakes are what we use to test usually.

20. Conclusion • Graphene has many obstacles to work around before it can be implemented into today’s technology. • Researchers are suggesting that it’s a matter of months rather than years for the next graphene break through. • Graphene has so many amazing properties, so expect it to impact many types of technologies.

21. References: • http://www.sciencedaily.com/releases/2012/09/120910082304.htm • De la Fuente, Jesus. www.graphene.com.13 April 2015 • Colapinto, John. “Graphene may be the most remarkable substance ever discovered. But what is it for?”.The New Yorker, 22 December, 2014.Web.13 April, 2015 • Wang, Brian.”Graphene Hybrid Supercapacitors storing as much as lead acid batteries which is six times commercial supercapacitors” www.nextbigfuture.com 17 April, 2015. Web 20 April, 2015. • Johnson, Dexter. “Graphene circuit competes head to head with Si technology.”www.spectrum.ieee.org 3 February, 2014.Web.20 April, 2014. • Malasarn, Davin. “UCLA Researchers develop new technique to scale up production of graphene micro super capacitors”. www.newsroom.ucla.edu. 19 February, 2013.Web. 20 April, 2015

22. Key Concepts • The first 2-D material ever discovered, only measuring 1-atom thick. • Lightest material ever discovered. • Strongest material ever discovered per unit weight. • Best electrical/thermal conductivity discovered at room temperature. • Currently does not possess a band-gap like a Si gate does.

23. Questions?