Measurement of Negative Differential Resistance Properties of Dipyridinium Self-Assembled Monolayers by Ultrahigh-Vacuum Scanning Tunneling Microscopy

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We fabricated organic monolayers onto a Au(111) substrate by the self-assembly method using 4-{4[4-(4-{1-[4-(4-acetylsulfanyl-phenylethynyl)-phenyl]-2,6-diphenyl-pyridinium-4-yl}-phenyl)-2,6-diphenyl-pyridinium-1-yl]-phenylethynyl}-phenylthioacetate (dipyridinium). Also, we selected an organic single molecule in the organic monolayers and measured their current–voltage ($I$–$V$) properties by ultrahigh-vacuum scanning tunneling microscopy (UHV-STM). Self-assembly monolayers (SAMs) were prepared on a Au(111) substrate that had been thermally deposited onto freshly cleaved, heated mica. The Au substrate was exposed to a 1 mM solution of 1-dodecanethiol in ethanol for 24 h to form a monolayer. After thoroughly rinsing the sample, it was exposed to a 0.3 mM solution of dipyridinium in tetrahydrofuran (THF) for 30 min. Finally, the electrical property of the organic monolayers was investigated by UHV-STM. The applied voltages were from $-2.0$ to $+2.0$ V at 299 K. The vacuum condition is $6\times 10^{-8}$ Torr. As a result, we confirmed the property of a negative differential resistance (NDR) in the positive-voltage region in between 1.5 and 2.0 V.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2006-01-15