Graphene Nano gap

1. Graphene Nano gap Phys 570X: Research Proposal Yusung Kim 04/29/2009

2. Outline • Introduction and Background • What is a nano gap and its use? • Studies on Graphene Nano gap • Current flow mechanisms in Graphene Nanogap • Motivation • Proposed Experiment and study

3. What is a nano gap and its use? Nano gap: Simply a gap of nano scale sizes between two electrodes or contacts Why are we interested? • Applications • Molecular electronics (Moletronics) • Measurement of electrical properties of molecules • Biosensors - Nano gap Field Effect Transistors • Two terminal memories - metal filamentary mechanism • Negative Differential Resistance observed in CNTs • Study of transport properties • Tunneling? • Filamentary mechanisms? • Spin-blockade Transport? [1] [2] resistance switching effect www.physics.mcgill.ca/SPM/JEOL/images/fig1.jpg

4. Recent studies on Carbon & Graphene Nano gap Devices Switching behaviors

5. Outline • Introduction and Background • What is a nano gap and its use? • Studies on Graphene Nano gap • Current flow mechanisms in Graphene Nanogap • Motivation • Proposed Experiment and study

6. Current flow Mechanisms Formation and breaking of linear chains of carbon atoms that bridge the gap under a strong electric field Filamentary Effect - Formation ofconducting path which bridge the gap sp3 insulating carbon switched to conductive sp2 conductive carbon by inducing electrical breakdown

7. Outline • Introduction and Background • What is a nano gap and its use? • Studies on Graphene Nano gap • Current flow mechanisms in Graphene Nanogap • Motivation • Proposed Experiment and study

8. Motivation • Although the effects of conduction process of nano gap formed by electric breakdown has been studied for quite a long time, sound explanation for the conduction process is lacking. • When electric breakdown method is used to form a nano gap, the control on the location of the gap has only been possible for nano wires or filaments in which the geometrical shape has to be patterned by lithography or etching techniques. We hope to use the sensitive nature of graphene material property to control the formation of a nano gap of large area which has not been performed yet. • The conduction process through the nano gap for graphene may be totally different from other nano gap devices due to its anomalous properties.

9. Outline • Introduction and Background • What is a nano gap and its use? • Studies on Graphene Nano gap • Current flow mechanisms in Graphene Nanogap • Motivation • Proposed Experiment and study

10. Proposed Experiment and Study 1. Control of the formation of the band gap Current Flow Drain Source Defect site Defect site is where the nano gap is likely to form Junction formed As Graphene is a very sensitive material to adsorbed atoms, the electronic properties may change and will eventuall cause a lot of scattering here and result in joule heating which leads to the formation of the nanogap at this point Different electronic properties in SLG and BLG may result in the formation of nano gap at the interface SLG - massless Bilayer

11. Proposed Experiment and Study 1. Control of the formation of the band gap Drain Current Flow Source Defect site Defect site is where the nano gap is likely to form Junction formed Current Flowing from a region with lots of channels to a region with relatively small channels would cause scattering mechanisms at the junction which may give same effect as a defect site. Geometrically bent graphene sheet may result in the formation of the gap at that location..

12. Proposed Experiment and Study 2. Study of the conduction process of nano gap structure Possibilities: • Filamentary process • After the electrical breakdown , there may be carbon left as a residue which may lead to the conduction process through percolation. • Singlet Triplet state conduction process observed in two coupled quantum dots may be possible which gives similar I-V characteristics – Spin blockaded Transport? (Magnetic zigzag edges) • Other possible interpretations… [3]

13. Proposed Experiment and Study In overall, our objectives include: • Fabrication of graphene nano gap in a controlled fashion. • Gather current flow data from our fabricated graphene device • Theoretical study of the conduction process which can best fit the data • Use theoretical formalisms to predict the performances of graphene-based memory devices or switches

14. Thank You!

15. References [1] C. Kerguerisa et al., “Electron transport through a metal-molecule-metal junction,” arXiv:cond-mat/9904037v2 [2] Y. Naitoh et al., “Non-volatile Resistance Switching using Single-Wall Carbon Nanotube Encapsulating Fullerene Molecules,” Applied Physics Express 2 (2009) 035008 [3] A.G Rinzler et al. (Smalley), “Unraveling Nanotube: Field Emission from an Atomic Wire,” Science, New Series, Vol. 269, No. 5230 (Sep. 15, 1995), pp. 1550-1553 [4] B. Standley et al., “Graphene-Based Atomic-Scale Switches,” Nano Lett., 2008, 8 (10) [5] Y. Li et al., (Tour) “Electronic two-terminal bistablegraphitic memories”Nature mat. Vol. 7 doi:10.1038/nmat2331 (2008) [6] Y. Naitoh et al., “Non-volatile Resistance Switching using Single-Wall Carbon Nanotube Encapsulating Fullerene Molecules,” Applied Physics Express 2 (2009) 035008 [7] D.E. Johnston et al., “Parallel Fabrication of NanogapElectrodes,” Nano Lett., 2007, 7 (9), pp 2774–2777 [8] F. Kreupl., et al., “Carbon-Based Resistive Memory,” arXiv:0901.4439v1 [cond-mat.mtrl-sci]