Organic Molecules on Silicon

The functionalization of semiconductor surfaces with organic molecules has attracted much interest, especially with respect to the challenges arising from the miniaturization in semiconductor device physics. In our group, we study the fundamental adsorption mechanism as well as the adsorption kinetics and dynamics of organic molecules on the Si(001) surface using scanning tunnelling microscopy (STM), photoelectron spectroscopy (XPS, UPS), molecular beam techniques and optical second-harmonic generation (SHG).

Adsorption Mechanism

Using scanning tunneling microscopy (STM) and photoelectron spectroscopy (XPS), we study fundamental adsorption mechanisms of different functional group. e.g. in the left figure, STM images of diethyl ether on Si(001) are shown for different surface temperatures. We can distinguish between different adsorption states, namely a datively bonded intermediate state at low temperature (top) and a covalently attached final state at room temperature (bottom).

Adsorption Dynamics

The adsorption dynamics are studied by means of molecular beam experiments using the King and Wells method and second-harmonic generation (SHG). The left figure shows typical measurements of the sticking coefficient of tetrahydrofuran (THF) on Si(001). At t = 0 s, the molecular beam hits the surface and the background pressure decreases due to the adsorption of THF on the surface. Depending on surface temperature, the initial sticking coefficient decreases, as desorption from the surface becomes more likely. By changing the kinetic energy of the molecular beam, the adsorption dynamics of THF is monitored (right figure). The lower initial sticking coefficient at higher kinetic energy implies an overall nonactivated adsorption process.



contact: Prof. Dr. Michael Dürr, Dr. Gerson Mette, Prof. Dr. Ulrich Höfer

Literature

  • T. Bohamud, M. Reutzel, A. Adamkiewicz, U. Höfer, and M. Dürr
    Electric field induced depolarization of Si-C bond leads to strongly reduced barrier for Alkyl-hopping on Si(001)
    J. Phys. Chem. C 124, 5270 (2020). DOI: 10.1021/acs.jpcc.0c00656
  • T. Bohamud, M. Reutzel, M. Dürr, and U. Höfer
    Dynamics of proton transfer reactions on Si(001)
    J. Chem. Phys. 150, 224703 (2019). DOI: 10.1063/1.5092804
  • G. Mette, A. Adamkiewicz, M. Reutzel, U. Koert, H. Dürr, and U. Höfer
    Controlling an SN2 reaction by electronic and vibrational excitation ‐ tip‐induced ether cleavage on Si(001)
    Angew. Chemie Int. Ed. 58, 3417 (2019). DOI: 10.1002/anie.201806777
  • C. Länger, J. Heep, P. Nikodemiak, T. Bohamud, P. Kirsten, U. Höfer, U. Koert, and M. Dürr
    Formation of Si/organic interfaces using alkyne-functionalized cyclooctynes – precursor-mediated adsorption of linear alkynes versus direct adsorption of cyclooctyne on Si(001)
    J. Phys.-Condens. Mat. 31, 034001 (2019). DOI: 10.1088/1361-648X/aaefc3
  • C. Länger, T. Bohamud, J. Heep, T. Glaser, M. Reutzel, U. Höfer, and M. Dürr
    Adsorption of methanol on Si(001): Reaction channels and energetics
    J. Phys. Chem. C 122, 14756 (2018). DOI: 10.1021/acs.jpcc.8b04583
  • J. Pecher, G. Mette, M. Dürr, and R. Tonner
    Site-specific reactivity of ethylene at distorted dangling bond configurations on Si(001)
    Chem. Phys. Chem. 18, 357 (2017). DOI: 10.1002/cphc.201601134
  • M. Reutzel, N. Münster, M. A. Lipponer, C. Länger, U. Höfer, U. Koert, and M. Dürr
    Chemoselective reactivity of bifunctional cyclooctynes on Si(001)
    J. Phys. Chem. C 120, 26284 (2016). DOI: 10.1021/acs.jpcc.6b0751
  • M. A. Lipponer, M. Reutzel, M. Dürr, and U. Höfer
    Energy Dependent Sticking Coefficients of Trimethylamine on Si(001) – Influence of the Datively Bonded Intermediate State on the Adsorption Dynamics
    Surf. Sci. 651, 118 (2016). DOI:10.1016/j.susc.2016.04.005
  • M. Reutzel, M. Lipponer, M. Dürr, and U. Höfer
    Binding Energy and Dissociation Barrier – Experimental Determination of the Key Parameters of the Potential Energy Curve of Diethyl Ether on Si(001)
    J. Phys. Chem. Lett. 6, 3971 (2015). DOI: 10.1021/acs.jpclett.5b01510
  • M. Reutzel, G. Mette, P. Stromberger, U. Koert, M. Dürr, and U. Höfer
    Dissociative adsorption of diethyl ether on Si(001) studied by means of scanning tunneling microscopy and photoelectron spectroscopy
    J. Phys. Chem. C 119, 6018 (2015). DOI: 10.1021/jp511780p
  • M. Lipponer, M. Dürr, and U. Höfer
    Adsorption dynamics of tetrahydrofuran on Si(001) studied by means of molecular beam techniques
    Chem. Phys. Lett. 624, 69 (2015). DOI: 10.1016/j.cplett.2015.02.008