Issue 20, 2010

Surface morphologies, electronic structures, and Kondo effect of lanthanide(iii)-phthalocyanine molecules on Au(111) by using STM, STS and FET properties for next generation devices

Abstract

The crystal structures of double-decker single-molecule magnets (SMMs) LnPc2 (Ln = Tb(III) and Dy(III); Pc = phthalocyanine) and non-SMM YPc2 were determined by using single crystal X-ray diffraction analysis. The compounds are isomorphous to each other. The compounds have metal-centers (M3+ = Tb, Dy, and Y) sandwiched by two Pc ligands via eight isoindole-nitrogen atoms in a square-antiprism fashion. The twist angle between the two Pc ligands is 41.4°. Scanning tunneling microscopy (STM) was used to investigate the compounds adsorbed on a Au(111) surface, deposited by using thermal evaporation in ultra-high vacuum. Both MPc2 with eight-lobes and MPc with four-lobes, which has lost one Pc ligand, were observed. In the scanning tunneling spectroscopy (STS) images of TbPc molecules at 4.8 K, a Kondo peak with a Kondo temperature (TK) of ∼250 K was observed near the Fermi level (V = 0 V). On the other hand, DyPc, YPc and MPc2 exhibited no Kondo peak. In order to understand the observed Kondo effect, the energy splitting of sublevels in a crystal field should be taken into consideration. As the next step in our studies on the SMM/Kondo effect in Tb-Pc derivatives, we investigated the electronic transport properties of Ln-Pc molecules as the active layer in top- and bottom-contact thin-film organic field effect transistor (OFETs) devices. Tb-Pc molecule devices exhibit p-type semiconducting properties with a hole mobility (μH) of ∼10−4 cm2 V−1 s−1. Interestingly, the Dy-Pc based devices exhibited ambipolar semiconducting properties with an electron mobility (μe) of ∼10−5 and a hole mobility (μH) of ∼10−4 cm2 V−1 s−1. This behavior has important implications for the electronic structure of the molecules.

Graphical abstract: Surface morphologies, electronic structures, and Kondo effect of lanthanide(iii)-phthalocyanine molecules on Au(111) by using STM, STS and FET properties for next generation devices

Supplementary files

Article information

Article type
Perspective
Submitted
10 Dec 2009
Accepted
10 Mar 2010
First published
15 Apr 2010

Dalton Trans., 2010,39, 4708-4723

Surface morphologies, electronic structures, and Kondo effect of lanthanide(III)-phthalocyanine molecules on Au(111) by using STM, STS and FET properties for next generation devices

K. Katoh, T. Komeda and M. Yamashita, Dalton Trans., 2010, 39, 4708 DOI: 10.1039/B926121D

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