Making Contact to Molecules: Interfacing to the Nanoworld

1. Making Contact to Molecules: Interfacing to the Nanoworld Peter Grutter Physics Department McGill University NSERC, FCAR, CIAR, McGill, IBM, CIHR, GenomeQuebec, CFI, NanoQuebec

2. What is Nanoelectronics?

3. What is Electronics? • By electronics we mean the handling of complicated electrical wave forms for communicatinginformation, probing (such as in radar) and data processing. • Data processing is the result of one complex stream of information interacting with another. • This requires non-linear behavior, otherwise information just gets passed on from one place to the other. (Landauer, Science 1968)

6. Contacts Structure-function relationship between transport process and molecular structure Dissipation Crosstalk (interconnects) Architecture I-O with a trillion processors Fault tolerance Manufacturing costs Molecular electronics: the issues

7. Does atomic structure of the contact matter? YES !

8. Does atomic structure of the contact matter? Mehrez, Wlasenko, et al., Phys. Rev. B 65, 195419 (2002)

9. Comparison of Experimental and Modeling Results Mehrez, Wlasenko, et al., Phys. Rev. B 65, 195419 (2002)

10. Calculating Conductance ‘Traditional’: infinite, structureless leads -> periodic boundary conditions. but: - result depends on lead size! - bias not possible due to periodic boundary condition! Jellium lead Jellium lead molecule

11. Calculation of electrical transport

12. lead ab-initio modelling of electronic transport

13. DFT plus non-equilibrium Green’s Functions J. Taylor, H. Guo , J. Wang, PRB 63, R121104 (2001) 1. Calculate long, perfect lead. Apply external potential V by shifting energy levels -> create electrode data base and get potential  right lead

14. 2. Solve Poisson equation for middle part (device plus a bit of leads); match wavefunctions  and potential as a function of V to leads (use data base) in real space. 3.  calculated with non-equilibrium Green’s functions (necessary as this is an open system). This automatically takes care of bound states

15. Contacts Structure-function relationship between transport process and molecular structure Dissipation Crosstalk (interconnects) Architecture I-O with a trillion processors Fault tolerance Manufacturing costs Molecular electronics: the issues

16. Reliable, chemically well defined contacts Cui et al. Nanotechnology 13, 5 (2002), Science 294, 571 (2001)

18. Low-T UHV STM/AFM/FIM 140K, 10-11mbar quick change between FIM - AFM/STM mode Stalder, Ph.D. Thesis 1995 Cross et al. PRL 80, 4685 (1998) Schirmeisen et al. NJP 2, 29.1 (2000)

19. Field Ion Microscopy (FIM) E. Muller, 1950’s

21. FIM of W(111) tip Imaging at 5.0 kV

22. FIM of W(111) tip Imaging at 5.0 kV Manipulating at 6.0 kV

23. FIM of W(111) tip Imaging at 5.0 kV Manipulating at 6.0 kV

24. FIM of W(111) tip Imaging at 5.0 kV Manipulating at 6.0 kV

25. Single Au atom on W(111) tip Imaged at 2.1 KV

26. W(111) tip on Au(111) Cross et al. PRL 80, 4685 (1998) Schirmeisen et al, NJP 2, 29.1 (2000)

27. Molecular Dynamics Simulations U. Landman et al, Science 248, 454 (1990)

28. W(111) trimer tip on Au(111) Ead = 21 eV l = 0.2 nm

29. Tip relaxation effects W tip on Au(111) surface Hofer, Fisher, Wolkow and Grutter Phys. Rev. Lett. 87, 236104 (2001)

30. Tip relaxation effects W tip on Au(111) surface Hofer, Fisher, Wolkow and Grutter Phys. Rev. Lett. 87, 236104 (2001)

31. F(z) and I(z) of W(111) trimer on Au(111) Schirmeisen et al, NJP 2, 29.1 (2000)

32. Yan Sun, Anne-Sophie Lucier Henrik Mortensen

33. The samples (measurements in progress) A) Au(111) 170 nm×170 nm, B) mixture of C6 and C8 thiol (ratio 6:1) on Au(111) 450nm×450nm C) C8 thiol, 6nm×6nm D) C8/C8 dithiol 36nm×36 nm.

34. Natural Process: Synaptic Transmission Experiment: Ligand-functionalized AFM tip Stimulation of Single Ligand-Gated Ion Channels Goal: To study channel gating kinetics and binding forces, while maintaining precise control of agonist location.

35. Tethering Scheme: GABA v.s. GABOB • Is it possible to tether a molecule of GABA without destroying its functionality? N. Cameron, B. Lennox (McGill)

36. Keeps the colloid complex soluble (?) Colloid simulates the AFM tip Tethering Scheme: Polymer Linker Au -S-(CH2)12-(O-CH2-CH2)23-O-GABOB {alkanethiol} {PEO}

37. Advanced microstructuring techniques are used to produce apertures in planar glass or quartz substrates. • Low noise recordings have been realized from both artificial lipid bilayers and whole cells. Planar Patch-Clamp Chips Fertig et. al.Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 2001 Oct;64(4-1):040901.

38. Ligand-receptor dissociation forces and rates depend on the rate at which the bond is ruptured!!! • Distinct binding states can be identified from a force v.s. loading rate plot. Most probable unbinding force: Loading Rate Dependent Unbinding: Good review: Evans, E. Annu. Rev. Biophys. Biomol. Struct. 2001. 30:105-28.

39. F(z) as a function of pulling speed Allows the determination of energy barriers and thus is a direct measure of the energy landscape in conformational space. Clausen-Schaumann et al., Current Opinions in Chem. Biol. 4, 524 (2000) Merkel et al., Nature 397, (1999) Evans, Annu. Rev. Biophys. Biomol. Struct., 30, 105 (2001)

40. Summary • Tools, both experimental and theoretical, drive our capabilities to understand the nanoworld! • We develop and apply SPM techniques to interface to: molecules and neurons in order to understand structure - property relationships

41. 14 graduate students, 6 post doctoral fellows Supported by NSERC, FCAR, CIAR, NanoQuebec CFI, IBM, GenomeQuebec, CIHR McGill Dawson Scholarship