Shuangzan Lu

Buckled Germanene Formation on Pt(111)

Germanene, a 2D honeycomb lattice analogous to graphene, is fabricated on a Pt(111) surface. It exhibits a buckled configuration with a (3 × 3) superlattice coinciding with the substrates (√19 × √19) superstructure. Covalent bonds exist throughout the germanene layer. The resulting high-quality germanene enables researchers to explore the fundamentals of germanene and its potential applications.

Direct Evidence of Dirac Signature in Bilayer Germanene Islands on Cu(111)

Bernal-stacked bilayer germanene with a stable buckled honeycomb structure has been successfully synthesized on Cu(111). Structural and electronic characterizations as well as theoretical calculations unequivocally demonstrate for the first time the presence of a nearly linear energy dispersion in the vicinity of the Fermi energy, as expected of the Dirac signature for theoretical freestanding germanene.

Ionic compound mediated rearrangement of 3, 4, 9, 10-perylene tetracarboxylic dianhydride molecules on Ag(100) surface

Tailoring of the assembly structure of organic molecular monolayer is of great importance to improve the performance of molecular devices. In this work, a typical ionic compound, namely KCl, was used to mediate the rearrangement of 3, 4, 9, 10-perylene tetracarboxylic dianhydride (PTCDA) monolayer on Ag(100). Combined scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) results indicate that both molecule and molecular superlattice would rotate after the dosing of KCl. The density functional theory calculation shows that KCl would exist in the form of molecules rather than ions on Ag(100) and demonstrates that experimentally observed structural transition induced by KCl molecules is energetically favored.

Nanostructured double-layer FeO as nanotemplate for tuning adsorption of titanyl phthalocyanine molecules

The growth, structure of Pt(111) supported double-layer FeO and the adsorption of titanyl phthalocyanine (TiOPc) molecules with tunable site and orientation were presented. According to the atomic-resolution STM image, the structure was rationalized as (8 root 3 x 8 root 3) R30 degrees/Pt(111) nanostructure constructed by Fe species coordinated with different number of oxygen on top of nonrotated (8 x 8) FeO/Pt(111) structure. Due to the modulation of the stacking of Fe atoms in the second layer relative to the O atoms in the second layer and the underlying layer, the interface and total dipole moment periodically vary within (8 root 3 x 8 root 3) R30 degrees/Pt(111) structure. The resulted periodically distributed dipole-dipole interaction benefits the growth of TiOPc molecules with area-selective sites and molecular orientations. Thus, this study provides a reliable method to govern the adsorption process of the polar molecules for potential applications in future functional molecular devices

Highly ordered molecular rotor matrix on a nanopatterned template: titanyl phthalocyanine molecules on FeO/Pt(111)

Molecular rotors, motors and gears play important roles in artificial molecular machines, in which rotor and motor matrices are highly desirable for large-scale bottom-up fabrication of molecular machines. Here we demonstrate the fabrication of a highly ordered molecular rotor matrix by depositing nonplanar dipolar titanyl phthalocyanine (TiOPc, C32H16N8OTi) molecules on a Moiré patterned dipolar FeO/Pt(111) substrate. TiOPc molecules with O atoms pointing outwards from the substrate (upward) or towards the substrate (downward) are alternatively adsorbed on the fcc sites by strong lateral confinement. The adsorbed molecules, i.e. two kinds of molecular rotors, show different scanning tunneling microscopy images, thermal stabilities and rotational characteristics. Density functional theory calculations clarify that TiOPc molecules anchoring upwards with high adsorption energies correspond to low-rotational-rate rotors, while those anchoring downwards with low adsorption energies correspond to high-rotational-rate rotors. A robust rotor matrix fully occupied by low-rate rotors is fabricated by depositing molecules on the substrate at elevated temperature. Such a paradigm opens up a promising route to fabricate functional molecular rotor matrices, driven motor matrices and even gear groups on solid substrates.

Fe on Sb(111): Potential Two-Dimensional Ferromagnetic Superstructures

It is highly desirable to fabricate two-dimensional ferromagnetic membranes based on orthodox magnetic elements because of their inherent magnetic properties. In this work, we report on two superstructures including a honeycomb-like lattice and identical nanocluster arrays formed by depositing Fe on Sb(111). Combined with first-principles calculations, both detailed atomic structures have been clarified. The honeycomb structure consists of a single layered Fe-Sb phase, and the cluster phase is assigned as a (3 × 3) Fe3Sb7 superlattice. Both structural phases exhibit high magnetic moments localized on d bands of Fe. Our results provide a method to fabricate 2D magnetic superstructures possessing great potential in the realization of the Haldane model, spintronics applications, and single atom catalysis.

Temperature Dependence of Spin Relaxation Time in InAs Columnar Quantum Dots at 10 to 50 K

1 Department of Applied Physics, Waseda University, Tokyo 169-8555, Japan Phone: +81-3-5286-3853, E-mail: nakasou10157@suou.waseda.jp 2 Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Dushu Lake Higher Education Town, Ruoshui Road 398, Szhou Industrial Park, Suzhou, China 3 Ecole Polytechnique Federale de Lausanne, Institute of Photonics and Quantum Electronics, Station 3, CH-1015 Lausanne, Switzerland 4 COBRA Research Institute, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands

Carrier spin relaxation in GaInNAsSb/GaNAsSb/GaAs quantum well

We have investigated the carrier spin relaxation in GaInNAsSb/GaNAsSb/GaAs quantum well (QW) by time‐resolved photoluminescence (PL) measurement. The sample consists of an 8‐nm‐thick GaIn0.36N0.006AsSb0.015 well, 5‐nm‐thick GaN0.01AsSb0.11 intermediate barriers and 100‐nm‐thick GaAs barriers grown by molecular beam epitaxy on a GaAs(100) substrate. The spin relaxation time and recombination lifetime at 10 K are measured to be 228 ps and 151 ps, respectively. As a reference, we have also obtained a spin relaxation time of 125 ps and a recombination lifetime of 63 ps for GaInNAs/GaNAs/GaAs QW. This result shows that crystal quality is slightly improved by adding Sb, although these short carrier lifetimes mainly originate from a nonradiative recombination. These spin relaxation times are longer than the 36 ps spin relaxation time of InGaAs/InP QWs and shorter than the 2 ns spin relaxation time of GaInNAs/GaAs QW.