TY - JOUR
T1 - Capacitance Behavior of Alkanethiol Self-Assembled Monolayer Studied by Scanning Tunneling Microscope Light Emission Spectroscopy
AU - Ahamed, Jamal Uddin
AU - Katano, Satoshi
AU - Uehara, Yoichi
N1 - Funding Information:
Part of this work was carried out in the Nano-Photoelectronics Laboratory, Tohoku University, Japan and was supported in part by the Tohoku University Electro-Related Departments Global COE Program. The Authors would like to thank Mr. Tomonori Sanbongi and Wataru Iida for their cooperation and technical assistance.
Publisher Copyright:
© 2016, The Indian Institute of Metals - IIM.
PY - 2016/10/1
Y1 - 2016/10/1
N2 - We have studied the capacitance behavior of alkanethiol self-assembled monolayer (SAM)-covered Au film by scanning tunneling microscope light emission (STM-LE) spectroscopy in the Kretschmann geometry. Although, the STM-LE from tip-sample gap into the vacuum (tip-side emission) is fundamentally weak and very difficult to detect, we have succeeded in detecting the STM-LE radiated into the prism (prism-side emission) by virtue of the enhancement of prism-coupled geometry. Our experimental results shows that the cutoff energy of STM-LE spectra have been redshifted with increase in thickness (chain length) of the SAM film. In order to explain the cutoff energy shift, we have designed a two-layer tunnel junction model by considering the capacitance response of the SAM film depending on the molecular chain length. It has been found from the model analysis, that the capacitance of the SAM changes with changing of the molecular thickness. Hence, it is concluded that the shift of the cutoff energy has originated from the change of the capacitance of the SAM film depending on the molecular chain length.
AB - We have studied the capacitance behavior of alkanethiol self-assembled monolayer (SAM)-covered Au film by scanning tunneling microscope light emission (STM-LE) spectroscopy in the Kretschmann geometry. Although, the STM-LE from tip-sample gap into the vacuum (tip-side emission) is fundamentally weak and very difficult to detect, we have succeeded in detecting the STM-LE radiated into the prism (prism-side emission) by virtue of the enhancement of prism-coupled geometry. Our experimental results shows that the cutoff energy of STM-LE spectra have been redshifted with increase in thickness (chain length) of the SAM film. In order to explain the cutoff energy shift, we have designed a two-layer tunnel junction model by considering the capacitance response of the SAM film depending on the molecular chain length. It has been found from the model analysis, that the capacitance of the SAM changes with changing of the molecular thickness. Hence, it is concluded that the shift of the cutoff energy has originated from the change of the capacitance of the SAM film depending on the molecular chain length.
KW - Capacitance response
KW - Cutoff energy
KW - Molecular chain length
KW - Redshift
KW - STM light emission
KW - Self-assembled monolayer
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U2 - 10.1007/s12666-015-0733-3
DO - 10.1007/s12666-015-0733-3
M3 - Article
AN - SCOPUS:84981180130
SN - 0019-493X
VL - 69
SP - 1579
EP - 1585
JO - Transactions of the Indian Institute of Metals
JF - Transactions of the Indian Institute of Metals
IS - 8
ER -