Direct Observation of Lanthanide(III)-Phthalocyanine Molecules on Au(111) by Using Scanning Tunneling Microscopy and Scanning Tunneling Spectroscopy and Thin-Film Field-Effect Transistor Properties of

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• 作者：Keiichi Katoh ; Yusuke Yoshida ; Masahiro Yamashita ; Hitoshi Miyasaka ; Brian K. Breedlove ; Takashi Kajiwara ; Shinya Takaishi ; Naoto Ishikawa ; Hironari Isshiki ; Yan Feng Zhang ; Tadahiro Komeda ; Masakazu
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：July 29, 2009
• 年：2009
• 卷：131
• 期：29
• 页码：9967-9976
• 全文大小：447K
• 年卷期：v.131,no.29(July 29, 2009)
• ISSN：1520-5126

文摘

The crystal structures of double-decker single molecule magnets (SMM) LnPc₂ (Ln = Tb(III) and Dy(III); Pc = phthalocyanine) and non-SMM YPc₂ were determined by using X-ray diffraction analysis. The compounds are isomorphous to each other. The compounds have metal centers (M = Tb³⁺, Dy³⁺, and Y³⁺) 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 was used to investigate the compounds adsorbed on a Au(111) surface, deposited by using the thermal evaporation in ultrahigh vacuum. Both MPc₂ with eight lobes and MPc with four lobes, which has lost one Pc ligand, were observed. In the scanning tunneling spectroscopy images of TbPc molecules at 4.8 K, a Kondo peak with a Kondo temperature (T_K) of 250 K was observed near the Fermi level (V = 0 V). On the other hand, DyPc, YPc, and MPc₂ exhibited no Kondo peak. 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 devices. Tb-Pc molecule devices exhibit p-type semiconducting properties with a hole mobility (μ_H) of 10⁻⁴ cm² V⁻¹ s⁻¹. Interestingly, the Dy-Pc based devices exhibited ambipolar semiconducting properties with an electron mobility (μ_e) of 10⁻⁵ and a μ_H of 10⁻⁴ cm² V⁻¹ s⁻¹. This behavior has important implications for the electronic structure of the molecules.