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Organic devices & potential mapping 3D simulations and experiments

TU / e. Organic devices & potential mapping 3D simulations and experiments. Dimitri Charrier , M. Kemerink and R.A.J. Janssen. Agenda. Scanning Kelvin Probe Microscope - why & basics SKPM - Problems Parameter free modeling Conclusions. Introduction. = I, , E, V. = organic device. tip.

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Organic devices & potential mapping 3D simulations and experiments

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  1. TU/e Organic devices & potential mapping3D simulations and experiments Dimitri Charrier, M. Kemerink and R.A.J. Janssen

  2. Agenda • Scanning Kelvin Probe Microscope - why & basics • SKPM - Problems • Parameter free modeling • Conclusions

  3. Introduction = I, , E, V = organic device

  4. tip Scanning Kelvin probe microscope • Interleave mode • Atomic Force Microscope in tapping mode • Surface potential at Lift Height ZL V Au Au V SiO2

  5. Principle: Force microscope F = force between tip and sample V = tip-sample voltage difference C = capacity between tip and sample Vdc = tip voltage Vac = amplitude voltage Vcpd = contact potential difference Then Vcpd= Vdc For F=0

  6. Experimental results true surface potential V = 10 V Au Au SiO2 Room temperature experiments 3D problem

  7. What is wrong? “the linear drop along the contacts […] “ Vexp < 10 V K.P. Puntambekar, P.V. Pesavento, and C.D. Frisbie Appl. Phys. Lett. 83, 5539 (2003)

  8. What is the real potential? Limited resolutions due to • Capacitive coupling between the tip and the surface SOURCE DRAIN (8 V)

  9. Analytical resolution? APEX CONTRIBUTION IN 2 DIMENSIONS CONE CONTRIBUTION IN 2 DIMENSIONS IT CAN WORK ONLY FOR SYMETRICAL PROBLEMS: APEX + CONE C. Argento and R.H. French, J. Appl. Phys. 80 (1996) 6081

  10. Steps of modeling Software used: COMSOL (Finite Element Method software) + MatLab 3D Drawing in COMSOL Olympus tip: Pt coat 2D simulations done in 2001 by T.S. Gross et al, Ultramicroscopy 87 (2001) 147

  11. Steps of modeling Meshing Zoom on meshing of the tip tip surface Discretization problem: finite amount of tetrahedrons Memory limit with 2 GB of RAM = 370 000 tetrahedrons

  12. Vertical resolution of modeling Scattering due to meshing limitation For obtaining good lateral resolution, first check the vertical resolution For each tip position we calculate the tip-sample force for few tip voltages, then we deduce the surface potential

  13. tip Modeling TRICK source channel drain MOVE THE SURFACE POTENTIAL AND NOT THE TIP OTHERWISE remeshing = scattering

  14. Modeling results - match perfectly Calculation time for ONE curve = 5 min X 3 voltages x 30 points8 hours

  15. Further results =  . Vx (Vsd/) Rescaling: Vx (Vsd) Modeling results

  16. Further results Au SiO2 Experimental results

  17. CONCLUSION • We developed a FREE-PARAMETER-FREE SKPM simulation tool, taking into account the lift height influence • Experimental data ≠ real potential due to the capacitive coupling • Experimental response of SKPM is understood • But: so far we cannot ‘invert the system response’

  18. Thanks to The M2N group René Janssen, Martijn Kemerink, Klara Maturova, Alexandre Nardes, Yingxin Liang, Ron Willems, Simon Mathijssen, … TU/e Technical University of Eindhoven The clean-room people Erik-Jan Geluk, Tjibbe de Vries, and Barry Smalbrugge

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