| AVS 61st International Symposium & Exhibition | |
| Scanning Probe Microscopy Focus Topic | Thursday Sessions |
| Session SP+AS+BI+NS+SS-ThA |
| Session: | Probing Chemical Reactions at the Nanoscale |
| Presenter: | Fabian Natterer, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland |
| Authors: | F.D. Natterer, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland F. Patthey, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland Y. Zhao, NIST J.E. Wyrick, NIST J.A. Stroscio, NIST H. Brune, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland |
| Correspondent: | Click to Email |
Inelastic electron tunneling spectroscopy (IETS) with the scanning tunneling microscope (STM) has vastly fueled the study of magnetic, electronic and vibrational properties of individual atoms and molecules due to its unmatched spatial and excellent energy resolution. Recently [1,2], rotational excitations could be characterized with IETS for the first time and yielded valuable insights into surface dynamics, bond lengths, and, notably about the nuclear spin state of homonuclear molecules. In particular, the two alike nuclei induce symmetry constraints in consequence of the Pauli principle and a certain alignment of nuclear spins requires a specific set of rotational levels J. We demonstrate rotational excitation spectroscopy (RES) with the STM for hydrogen, its isotopes, and mixtures thereof, physisorbed on metal supported graphene and hexagonal boron nitride, as well as on exfoliated graphene devices. We observe excitation energies that are equivalent with rotational transitions (ΔJ = 2) of molecules in the gas phase for hydrogen, hydrogen-deuteride, and deuterium, respectively. Notably, these values represent the nuclear spin isomers para-H2 and ortho-D2. For HD, an additional J = 0 → 1 transition is discerned, which is allowed for heteronuclear diatomics. We discuss the excitation mechanism in the light of resonant enhanced tunneling [3,4], and illustrate how the dynamics of molecules could be controlled by applying an electric field using a back gating graphene device geometry [5].
[1] F. D. Natterer, F. Patthey, H. Brune, Phys. Rev. Lett.111, 175303 (2013)
[2] Li et al., Phys. Rev. Lett.111, 146102 (2013)
[3] F. D. Natterer, F. Patthey, H. Brune, arXiv:1403.1312 (2014)
[4] B. N. Persson, A. Baratoff, Phys. Rev. Lett. 59, 339 (1987)
[5] J. Chae et al.,Phys. Rev. Lett.109, 116802 (2012)
Funding from the Swiss National Science Foundation under project number 148891 is greatly appreciated.