7 October 2014 Interface formation between pentacene and silver contacts investigated by surface-enhanced Raman spectroscopy
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Interface formation between organic semiconductors and substrates or electrodes is of great interest to develop functional devices. In this paper we discuss on the interface formation between the organic semiconductor pentacene and silver as the top electrode. Pentacene is commonly used as active layer in organic field-effect transistors (OFETs). It is known that in OFEts significant percentage of the drain current is realized at organic layer thickness below 5 nm. Therefore, understanding the monolayer regime is vital to identify the physics and chemistry of the organic semiconductor. We report Raman spectroscopy measurements of 1.5 nm pentacene films deposited under high vacuum conditions onto Au or SiO2 and covered by silver contacts. In order to achieve a detailed molecular identity upon metal evaporation, Raman spectra at each evaporation stage was recorded. Analysis proved that a bare 1.5 nm pentacene film on smooth Au substrates reflects significant enhancement of the Raman signal. Silver contact of about 1 nm thickness promotes enhancement of the Raman internal vibrational modes along the activation of normally infrared-active modes, and the enhancement factors are estimated to be close to 100. The Raman spectroscopy measurements indicate absence of metallorganic pentacene-Ag complexes regardless of the substrate.
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Beynor A. Paez-Sierra, Beynor A. Paez-Sierra, Diana Maritza Marulanda, Diana Maritza Marulanda, Hernán Rodríguez, Hernán Rodríguez, "Interface formation between pentacene and silver contacts investigated by surface-enhanced Raman spectroscopy", Proc. SPIE 9185, Organic Field-Effect Transistors XIII; and Organic Semiconductors in Sensors and Bioelectronics VII, 918521 (7 October 2014); doi: 10.1117/12.2062367; https://doi.org/10.1117/12.2062367

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