TY - JOUR
T1 - Experimental Observation of Real Time Molecular Dynamics Using Electromigrated Tunnel Junctions
AU - Bellisario, Darin O.
AU - Liu, Albert Tianxiang
AU - Kozawa, Daichi
AU - Han, Rebecca
AU - Harris, Jasmine K.
AU - Zabala, Robert Brandon
AU - Wang, Qing
AU - Agrawal, Kumar V.
AU - Son, Youngwoo
AU - Strano, Michael S.
N1 - Funding Information:
Device fabrication was performed in part at the MIT Research Laboratory for Electronics’ (RLE) Scanning Electron Beam Lithography (SEBL) facility and the Harvard Center for Nanoscale Studies (CNS). Mark Mondol at the RLE SEBL facility provided invaluable consultation on nanowire device fabrication. SEM device characterization was performed at the MIT Institute of Soldier Nanotechnologies (ISN). DOB would like to thank the Department of Defense for a National Defense Science & Engineering Graduate Fellowship and the American Physical Society for a Ovshinsky Sustainable Energy Fellowship.
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/10/12
Y1 - 2017/10/12
N2 - Single molecule tunnel junctions (SMTJs) can provide important physical insights into electronic and vibrational phenomena at the molecular scale. However, observations and analysis are typically confined to sufficiently low temperatures as to suppress molecular motion and the resulting stochastic fluctuations in the tunneling current. In this work, we introduce and experimentally validate a methodology whereby a slightly higher temperature (9 K) compared to a typical SMTJ study can be used to induce sparse fluctuations in the inelastic tunneling current and provide the fingerprints of dynamics between the conformational states of the molecule. Two examples of benzene dithiol and cysteine are studied in electromigratively formed W/Au nanowire SMTJs on SiO2 at 9 K. The second-order transform of the tunneling current reveals the expected vibrational spectra. However, we show that temporal fluctuations can be analyzed using a hidden Markov Model to reveal dynamics assigned to millisecond rearrangements of the molecule, with apparent energy barriers ranging from 35 to 66 meV, consistent with theoretical predictions. The observed transitions are consistent with a model of lateral migration of the thiol-anchored molecules in an asymmetric junction. The use of temperature in SMTJs in this way can provide new insights into molecule dynamics in confined volumes and at electrode interfaces.
AB - Single molecule tunnel junctions (SMTJs) can provide important physical insights into electronic and vibrational phenomena at the molecular scale. However, observations and analysis are typically confined to sufficiently low temperatures as to suppress molecular motion and the resulting stochastic fluctuations in the tunneling current. In this work, we introduce and experimentally validate a methodology whereby a slightly higher temperature (9 K) compared to a typical SMTJ study can be used to induce sparse fluctuations in the inelastic tunneling current and provide the fingerprints of dynamics between the conformational states of the molecule. Two examples of benzene dithiol and cysteine are studied in electromigratively formed W/Au nanowire SMTJs on SiO2 at 9 K. The second-order transform of the tunneling current reveals the expected vibrational spectra. However, we show that temporal fluctuations can be analyzed using a hidden Markov Model to reveal dynamics assigned to millisecond rearrangements of the molecule, with apparent energy barriers ranging from 35 to 66 meV, consistent with theoretical predictions. The observed transitions are consistent with a model of lateral migration of the thiol-anchored molecules in an asymmetric junction. The use of temperature in SMTJs in this way can provide new insights into molecule dynamics in confined volumes and at electrode interfaces.
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U2 - 10.1021/acs.jpcc.7b08228
DO - 10.1021/acs.jpcc.7b08228
M3 - Article
AN - SCOPUS:85031321219
SN - 1932-7447
VL - 121
SP - 22550
EP - 22558
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 40
ER -