In Situ Microscopy and Spectroscopy Poster session

Thursday, October 31, 2013 6:00 PM in Room Hall B

IS-ThP-1 Scanning Tunneling Microscopy of the Topological Crystalline Insulator SnTe
Duming Zhang, Jeonghoon Ha (NIST and University of Maryland); Hongwoo Baek (NIST and Seoul National University, Republic of Korea); Young Kuk (Seoul National University, Republic of Korea); Joseph Stroscio (Center for Nanoscale Science and Technology, NIST)
Recently, the topological classification of electronics states has been extended to a new class of matter called topological crystalline insulators. In contrast to topological insulators characterized by time reversal symmetry protected surface states with an odd number of Dirac cones, topological crystalline insulators arise from crystal symmetry and are characterized by surface states with an even number of Dirac cones. Here, we report in-situ low temperature scanning tunneling microscopy study of SnTe (001) surfaces grown by molecular beam epitaxy. SnTe high symmetry surfaces have been recently predicted and experimentally confirmed as hosting topological crystalline insulator surface states [1-3]. The growth of SnTe on multilayer graphene/SiC substrates is shown to produce SnTe (001) nanoplates with varying densities of Sn vacancies. The topological surface states on the SnTe (001) surface in these nanoplates were probed by scanning tunneling spectroscopic mapping. In this poster we discuss the spectroscopic mapping results in terms of scattering in Fermi surface contours of the topological surface states.

[1] T. H. Hsieh, et al., Nat. Comm. 3, 982 (2012).

[2] Y. Tanaka, et al., Nat. Phys. 8, 800 (2012).

[3] S.-Y. Xu, et al., Nat. Comm. 3, 1192 (2012).

IS-ThP-2 In Situ Electrostatic and Thermal Manipulation of Suspended Graphene Membranes
Wenzhong Bao, Kevin Myhro, Z. Zhao, Z. Chen, W. Jang, Lei Jing, F. Miao, H. Zhang, C. Dames, ChunNing Lau (University of California, Riverside)
Graphene is nature’s thinnest elastic membrane, and its morphology has important impacts on its electrical, mechanical, and electromechanical properties. Here we report manipulation of the morphology of suspended graphene via electrostatic and thermal control. By measuring the out-of-plane deflection as a function of applied gate voltage and number of layers, we show that graphene adopts a parabolic profile at large gate voltages with inhomogeneous distribution of charge density and strain. Unclamped graphene sheets slide into the trench under tension; for doubly clamped devices, the results are well-accounted for by membrane deflection with effective Young’s modulus E = 1.1 TPa. Upon cooling to 100 K, we observe buckling-induced ripples in the central portion and large upward buckling of the free edges, which arises from graphene’s large negative thermal expansion coefficient.
IS-ThP-3 Slow-Light Biomolecule Self-Trapping Sensor for Point-of-Care Applications
Khaled Mnaymneh (University of Michigan)

Slow-Light Biomolecule Self-Trapping Sensor

for Point-of-Care Applications

K. Mnaymneh1, M.-T. Chung2, P. Chen3 and K. Kurabayashi1,3

1Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, USA

2Electrical Engineering, University of Southern California, Los Angeles, California, USA

3Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, USA

While pathogenic bimolecular detection techniques based upon bio-labeling, such as ELISA, are widely used in clinical settings, they require many hours and several steps to achieve results creating long patient wait times that may, in some cases, prove dire. Furthermore, such systems are not portable nor compact requiring time-critical samples be shipped to labs far from the point-of-care adding further delays. However, with the advent of label-free techniques, problems such as the ones outlined may soon be a thing of the past.

In this talk, we present a compact, label-free optical biosensor based upon slow-light photonic crystal architecture [1] designed to both trap single biomolecules and provide high-sensitivity interferometry for single-particle detection. By integrating a robust cavity design for trapping [2] into a slow-light waveguide design, we combine the ability to trap single biomolecules and optical interrogate their properties in a compact, label-free environment ideal for point-of-care applications. The biomolecules are prepared, flowed and analyzed in a PDMS multi-chamber unit with the photonic crystal sensor housed in one of those units down-stream. After cell stimulation, the biomolecules of interested mix with anti-gen nanoparticles, bind and then flow towards the slow-light sensor where the nanoparticles are trapped and analyzed in a label-free and re-useable manner. The presentation will show coupled-mode theory and simulation results that indicate promising values for both trapping force, phase-sensitivity and compactness.

[1] K. Mnaymneh, et al., Opt. Lett. 37, 280 (2013)

[2] N. Descharmes, et al., Phys. Rev. Lett 110, 123601 (2013)