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Variation of the contact resistance with electric current for gold electrodes on a squaraine single crystal
Author(s) -
Govor Leonid V.,
Reiter Günter,
Parisi Jürgen
Publication year - 2015
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201532241
Subject(s) - electrode , contact resistance , materials science , crystal (programming language) , single crystal , analytical chemistry (journal) , metal , voltage , chemistry , optoelectronics , electrical engineering , crystallography , metallurgy , organic chemistry , computer science , programming language , engineering
We examined the dependence of the contact resistances between gold electrodes and a single crystal of small organic molecules, namely, squaraine (2,4‐bis[4‐(N,N‐diisobutylamino)‐2,6‐dihydroxyphenyl]), on the electric current. Applying four gold electrodes on the crystal allows to measure twelve current–voltage ( I − V ) characteristics. The dependence of all eight contact resistances (four for the injecting and four for the extracting electrodes, respectively) on the electric current was determined. We found: (i) the contact resistance of all electrodes (ranging from ≃ 10 5 to ≃ 10 8 Ω ) was larger than the resistance of the squaraine crystal ( ≤ 10 5 Ω ); (ii) for the same electrode, the values of the resistance for charge injection and charge extraction were different; (iii) the values of all contact resistances were not constant, but depended on the value of the current. Furthermore, each of the measured total I – V characteristics could be decomposed into three components representing charge transfer through the injecting electrode, the squaraine crystal, and the extracting electrode. We demonstrate that, for the correct interpretation of the I – V characteristics measured on metal/squaraine/metal structures, determination of the contact resistances at the interface between metal electrode and organic crystal is ultimately crucial.