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AFM for Graphene and 2D Materials

Graphene AFM image: flakes imaged on boron nitride using atomic force microscopy

The 2004 report by Novoselov and Geim on transistors made from single-layer graphitic films created overnight the field of graphene AFM research. This single, free-standing plane of carbon atoms has proven to exhibit many unique and desirable properties: it provides a high surface area, excellent electrical and thermal conductivity, and superior mechanical strength. Graphene is an ideal two-sided surface without a bulk in between, has the highest known room-temperature carrier mobility, 25 times the thermal conductivity of silicon, a reported Young's modulus of ~1 TPa and breaking strength approaching the theoretical limit. Potentials for breakthrough technologies thus abound, including: next generation electronics (quantum computing, spintronics); energy collection and storage (photovoltaics, fuel cells, supercapacitors); nanoelectromechanical (NEMS) devices and resonators; and electrochemical sensors and lab-on-chip biosensors. This has also spurred attendant interest in other 2D materials such as MoS2 and boron nitride films.
 
Atomic force microscopy is a critical enabling technology in graphene research. Its high (sub-angstrom) resolution distinguishes with ease single atomic layers on a substrate, and is suitable for characterizing film quality, such as morphology, roughness, and uniformity. Moreover, AFM imaging requires a probe to be in physical contact with the surface, which makes it possible to determine electrical and mechanical properties simultaneously with topography. Material properties such as conductivity and permittivity, stiffness and dissipation, viscoelastic and friction responses can thus be mapped-out with nanoscale lateral precision. Long-range electrical properties such as electrostatic charge, surface potential, and magnetic fields can be probed as well by bringing the tip in close proximity of the surface during measurement.

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Metrology

  • Film thickness
  • Roughness, morphology, uniformity

Electrical Properties

  • Conductivity and permittivity (sMIM, CAFM)
  • Surface potential (KPFM)
  • Stored charge (EFM)
  • I-V profiles (CAFM)

Magnetic Properties

  • Magnetic force gradients (MFM)

Mechanical Properties

  • Stiffness, Young's modulus (Force Curves, Fast Force Mapping, AM-FM)
  • Elastic modulus, loss modulus, loss tangent (AM-FM, Contact Resonance, Loss Tangent Imaging)
  • Energy dissipation (AM-FM, Contact Resonance, Loss Tangent Imaging)

Tribological Properties

  • Friction (LFM)
  • Adhesion (Force Curves, Fast Force Mapping)

Thermal Properties

  • Thermal conductivity (SThM)
  • Quantum computing, spintronics
  • Electronic circuit components: transistors, field emitters, interconnects, supercapacitors
  • Resistive non-volatile memory technology
  • Transparent electrodes for optoelectronics, photovoltaics, and display technology
  • Energy collection and storage: solar cells, fuel cells, batteries
  • Terahertz plasmon oscillators
  • Sensor technologies: single-molecule sensors, electrochemical sensors, biosensors, lab-on-chip devices
  • Semipermeable membranes for (bio)molecular and ion transport
  • Nanoelectromechanical systems and mechanical resonators

"Direct growth of high crystallinity graphene from water-soluble polymer powders," Q. Chen, Y. Zhong, M. Huang, G. Zhao, Z. Zhen, and H. Zhu, 2D Mater. 5, 035001 (2018). https://doi.org/10.1088/2053-1583/aab729

"Multi-terminal memtransistors from polycrystalline monolayer molybdenum disulfide," V. K. Sangwan, H. S. Lee, H. Bergeron, I. Balla, M. E. Beck, K. S. Chen, and M. C. Hersam, Nature 554, 500 (2018). https://doi.org/10.1038/nature25747

"Robust microscale superlubricity under high contact pressure enabled by graphene-coated microsphere," S. W. Liu, H. P. Wang, Q. Xu, T. B. Ma, G. Yu, C. Zhang, D. Geng, Z. Yu, S. Zhang, W. Wang, Y. Z. Hu, H. Wang, and J. Luo, Nat. Commun. 8, 14029 (2017). https://doi.org/10.1038/ncomms14029

"Domain-wall conduction in ferroelectric BiFeO3 controlled by accumulation of charged defects," T. Rojac, A. Bencan, G. Drazic, N. Sakamoto, H. Ursic, B. Jancar, G. Tavcar, M. Makarovic, J. Walker, B. Malic, and D. Damjanovic, Nat. Mater. 16, 322 (2017). https://doi.org/10.1038/nmat4799

"A novel approach to decrease friction of graphene," X. Zeng, Y. Peng, and H. Lang, Carbon 118, 233 (2017). https://doi.org/10.1016/j.carbon.2017.03.042

"Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes," F. Liu, L. You, K. L. Seyler, X. Li, P. Yu, J. Lin, X. Wang, J. Zhou, H. Wang, H. He, S. T. Pantelides, W. Zhou, P. Sharma, X. Xu, P. M. Ajayan, J. Wang, and Z. Liu, Nat. Commun. 7, 12357 (2016). https://doi.org/10.1038/ncomms12357

"Covalent functionalization and passivation of exfoliated black phosphorus via aryl diazonium chemistry," C. R. Ryder, J. D. Wood, S. A. Wells, Y. Yang, D. Jariwala, T. J. Marks, G. C. Schatz, and M. C. Hersam, Nat. Chem. 8, 597 (2016). https://doi.org/10.1038/nchem.2505

"Strain-engineered graphene grown on hexagonal boron nitride by molecular beam epitaxy," A. Summerfield, A. Davies, T. S. Cheng, V. V. Korolkov, Y. J. Cho, C. J. Mellor, C. T. Foxon, A. N. Khlobystov, K. Watanabe, T. Taniguchi, L. Eaves, S. V. Novikov, and P. H. Beton, Sci. Rep. 6, 22440 (2016). https://doi.org/10.1038/srep22440

"Large-area epitaxial monolayer MoS2," D. Dumcenco, D. Ovchinnikov, K. Marinov, P. Lazić, M. Gibertini, N. Marzari, O. Lopez Sanchez, Y.-C. Kung, D. Krasnozhon, M.-W. Chen, S. Bertolazzi, P. Gillet, A. Fontcuberta i Morral, A. Radenovic, and A. Kis, ACS Nano 9, 4611 (2015). https://doi.org/10.1021/acsnano.5b01281

"Planar carbon nanotube-graphene hybrid films for high-performance broadband photodetectors," Y. Liu, F. Wang, X. Wang, X. Wang, E. Flahaut, X. Liu, Y. Li, X. Wang, Y. Xu, Y. Shi, and R. Zhang, Nat. Commun. 6, 8589 (2015). https://doi.org/10.1038/ncomms9589

"Gate-tunable memristive phenomena mediated by grain boundaries in single-layer MoS2," V. K. Sangwan, D. Jariwala, I. S. Kim, K. S. Chen, T. J. Marks, L. J. Lauhon, and M. C. Hersam, Nat. Nanotechnol. 10, 403 (2015). https://doi.org/10.1038/nnano.2015.56

"Strong oxidation resistance of atomically thin boron nitride nanosheets," L. H. Li, J. Cervenka, K. Watanabe, T. Taniguchi, and Y. Chen, ACS Nano 8, 1457 (2014). https://doi.org/10.1021/nn500059s

"Fluorination of graphene enhances friction due to increased corrugation," Q. Li, X.-Z. Liu, S.-P. Kim, V. B. Shenoy, P. E. Sheehan, J. T. Robinson, and R. W. Carpick, Nano Lett. 14, 5212 (2014). https://doi.org/10.1021/nl502147t

"Exploring flatland: AFM of mechanical and electrical properties of graphene, MoS2 and other low-dimensional materials," S. Bertolazzi, J. Brivio, A. Radenovic, A. Kis, H. Wilson, L. Prisbrey, E. Minot, A. Tselev, M. Philips, M. Viani, D. Walters, and R. Proksch, Microscopy and Analysis 27, 21 (2013). link to magazine

"Scalable one-step wet-spinning of graphene fibers and yarns from liquid crystalline dispersions of graphene oxide: Towards multifunctional textiles," R. Jalili, S. H. Aboutalebi, D. Esrafilzadeh, R. L. Shepherd, J. Chen, S. Aminorroaya-Yamini, K. Konstantinov, A. I. Minett, J. M. Razal, and G. G. Wallace, Adv. Funct. Mater. 23, 5345 (2013). https://doi.org/10.1002/adfm.201300765

"Friction force microscopy: a simple technique for identifying graphene on rough substrates and mapping the orientation of graphene grains on copper," A. J. Marsden, M. Phillips, and N. R. Wilson, Nanotechnology 24, 255704 (2013). https://doi.org/10.1088/0957-4484/24/25/255704

"Near-field microwave scanning probe imaging of conductivity inhomogeneities in CVD graphene," A. Tselev, N. V. Lavrik, I. Vlassiouk, D. P. Briggs, M. Rutgers, R. Proksch, and S. V. Kalinin, Nanotechnology 23, 385706 (2012). https://doi.org/10.1088/0957-4484/23/38/385706

"Stretching and breaking of ultrathin MoS2," S. Bertolazzi, J. Brivio, and A. Kis, ACS Nano 5, 9703 (2011). https://doi.org/10.1021/nn203879f

"Grains and grain boundaries in single-layer graphene atomic patchwork quilts," P. Y. Huang, C. S. Ruiz-Vargas, A. M. van der Zande, W. S. Whitney, M. P. Levendorf, J. W. Kevek, S. Garg, J. S. Alden, C. J. Hustedt, Y. Zhu, and J. Park, Nature 469, 389 (2011). https://doi.org/10.1038/nature09718

"Multiply folded graphene," K. Kim, Z. Lee, B. D. Malone, K. T. Chan, B. Aleman, W. Regan, W. Gannett, M. F. Crommie, M. L. Cohen, and A. Zettl, Phys. Rev. B 83, 245433 (2011). https://doi.org/10.1103/physrevb.83.245433

"Single-layer MoS2 transistors," B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, Nat. Nanotechnol. 6, 147 (2011). https://doi.org/10.1038/nnano.2010.279

"The large-scale production of graphene flakes using magnetically-enhanced arc discharge between carbon electrodes," I. Levchenko, O. Volotskova, A. Shashurin, Y. Raitses, K. Ostrikov, and M. Keidar, Carbon 48, 4570 (2010). https://doi.org/10.1016/j.carbon.2010.07.055

"Layer-by-layer transfer of multiple, large area sheets of graphene grown in multilayer stacks on a single SiC wafer," S. Unarunotai, J. C. Koepke, C.-L. Tsai, F. Du, C. E. Chialvo, Y. Murata, R. Haasch, I. Petrov, N. Mason, M. Shim, J. Lyding, and J. A. Rogers, ACS Nano 4, 5591 (2010). https://doi.org/10.1021/nn101896a

"Effective doping of single-layer graphene from underlying SiO2 substrates," Y. Shi, X. Dong, P. Chen, J. Wang, and L.-J. Li, Phys. Rev. B 79, 115402 (2009). https://doi.org/10.1103/physrevb.79.115402