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 Tb(III)- and Dy(III)-Phthalocyanine Molecules

Abstract

The crystal structures of double-decker single molecule magnets (SMM) LnPc(2) (Ln = Tb(III) and Dy(III); Pc = phthalocyanine) and non-SMM YPc(2) were determined by using X-ray diffraction analysis. The compounds are isomorphous to each other. The compounds have metal centers (M = Tb(3+), Dy(3+), and Y(3+)) 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 degrees. 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 MPc(2) 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 approximately 250 K was observed near the Fermi level (V = 0 V). On the other hand, DyPc, YPc, and MPc(2) 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 (mu(H)) of approximately 10(-4) cm(2) V(-1) s(-1). Interestingly, the Dy-Pc based devices exhibited ambipolar semiconducting properties with an electron mobility (mu(e)) of approximately 10(-5) and a mu(H) of approximately 10(-4) cm(2) V(-1) s(-1). This behavior has important implications for the electronic structure of the molecules.

Spin and charge dynamics in[TbPc2]0and[Branzoli1, Carretta2, Filibian3 et al. 2010Phys. Rev. B341290View full textAdd to dashboardCite

“…The [LnPc 2 ] 0 molecules crystallized in the space group P 2 1 2 1 2 1 (γ-phase) as reported in Ref. 15 and were isomorphous to each other.…”

Bis(phthalocyaninato)yttrium grown on Au(111): Electronic structure of a single molecule and the stability of two-dimensional films investigated by scanning tunneling microscopy/spectroscopy at 4.8 K

“…4(d) and 4(f)). These abnormal HOMO/ LUMO images may indicate that these molecules are located in a different chemical environment from the neighboring ones [28].…”

Metal-free phthalocyanine (H2Pc) molecule adsorbed on the Au(111) surface: formation of a wide domain along a single lattice direction

“…Scanning tunneling microscopy (STM) has played an important role in the characterization of Pc films [6]. However, STM can only reveal the topmost surface, and the direct information of the interface cannot be obtained with this technique [7][8][9][10]. In studying the adsorption of the double-layer molecules, it might be necessary to compare the results with those obtained on metal-free Pc, as the bottom Pc layer does not contain a metal atom.…”