Carlos Manzano

Manipulating molecular quantum states with classical metal atom inputs: demonstration of a single molecule NOR logic gate.

Quantum states of a trinaphthylene molecule were manipulated by putting its naphthyl branches in contact with single Au atoms. One Au atom carries 1-bit of classical information input that is converted into quantum information throughout the molecule. The Au-trinaphthylene electronic interactions give rise to measurable energy shifts of the molecular electronic states demonstrating a NOR logic gate functionality. The NOR truth table of the single molecule logic gate was characterized by means of scanning tunnelling spectroscopy.

Mapping the Excited States of Single Hexa-peri-benzocoronene Oligomers

Electronic states of a molecule are usually analyzed via their decomposition in linear superposition of multielectronic Slater determinants built up from monoelectronics molecular orbitals. It is generally believed that a scanning tunneling microscope (STM) is able to map those molecular orbitals. Using a low-temperature ultrahigh vacuum (LT-UHV) STM, the dI/dV conductance maps of large single hexabenzocoronene (HBC) monomer, dimer, trimer, and tetramer molecules were recorded. We demonstrate that the attribution of a tunnel electronic resonance to a peculiar π molecular orbital of the molecule (or σ intermonomer chemical bond) in the STM junction is inappropriate. With an STM weak-measurement-like procedure, a dI/dV resonance results from the conductance contribution of many molecular states whose superposition makes it difficult to reconstruct an apparent molecular orbital electron probability density map.

Mapping the first electronic resonances of a Cu phthalocyanine STM tunnel junction

Using a low temperature, ultrahigh vacuum scanning tunneling microscope (STM), dI/dV differential conductance maps were recorded at the tunneling resonance energies for a single Cu phthalocyanine molecule adsorbed on an Au(111) surface. We demonstrated that, contrary to the common assumption, such maps are not representative of the molecular orbital spatial expansion, but rather result from their complex superposition captured by the STM tip apex with a superposition weight which generally does not correspond to the native weight used in the standard Slater determinant basis set. Changes in the molecule conformation on the Au(111) surface further obscure the identification between dI/dV conductance maps and the native molecular orbital electronic probability distribution in space.

Electronic properties of atomically thin MoS2 layers grown by physical vapour deposition: band structure and energy level alignment at layer/substrate interfaces

We present an analysis of the electronic properties of an MoS2 monolayer (ML) and bilayer (BL) as-grown on a highly ordered pyrolytic graphite (HOPG) substrate by physical vapour deposition (PVD), using lab-based angle-resolved photoemission spectroscopy (ARPES) supported by scanning tunnelling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) for morphology and elemental assessments, respectively. Despite the presence of multiple domains (causing in-plane rotational disorder) and structural defects, electronic band dispersions were clearly observed, reflecting the high density of electronic states along the high symmetry directions of MoS2 single crystal domains. In particular, the thickness dependent direct-to-indirect band gap transition previously reported only for MoS2 layers obtained by exfoliation or via epitaxial growth processes, was found to be also accessible in our PVD grown MoS2 samples. At the same time, electronic gap states were detected, and attributed mainly to structural defects in the 2D layers. Finally, we discuss and clarify the role of the electronic gap states and the interlayer coupling in controlling the energy level alignment at the MoS2/substrate interface.

High Voltage STM Imaging of Single Copper Phthalocyanine

In this chapter experiments done to investigate the scanning tunneling microscope (STM) imaging at near field emission voltages of single Copper Phthalocyanine (CuPc) molecules deposited on Au(111) are presented. An imaging bias voltage range is explored exceeding the standard tunneling imaging conditions going from the threshold of the tunneling junction barrier up to −10.0 V. At this voltage regime current transmitted through the tip-molecule–substrate junction is made not only of tunneling electrons but also of electrons overcoming the tunneling barrier and behaving like free electrons. Our interpretation of the process, enabling the visualization of the electronic cloud of single organic molecules under these conditions, is presented.

Nanogears Mechanics: From a Single Molecule to Solid-State Nanogears on a Surface

The first experimental demonstration of a controllable rotating molecule gear is presented. A scanning tunneling microscope (STM) is used to construct, manipulate, and observe the rotation of the molecule gear. The appropriate combination of molecule design, molecule manipulation protocol, and surface atomic structure selection leads to the functioning of the molecule gear. Rotation of the molecule gear is done step-by-step and totally under control. The fabrication of solid-state SiO2 nanogears with diameters ranging from 30 nm up to 1 μm and their manipulation using an atomic force microscope tip on a graphite surface is also presented. Ranging in sizes from few tens of nanometers up to submicron diameters, they are going to enable the transmission of mechanical motion from functional mechanical molecule machineries to larger submicron or micron-sized devices through series of solid-state gears and mechanical components compatible with the semiconductor and electronics industry technology.

Mapping the Electronic Resonances of Single Molecule STM Tunnel Junctions

In this chapter is presented how the electron probability distributions of molecular states are imaged in real space using scanning tunneling microscopy. Differential tunneling conductance images of selected single molecules taken at voltages corresponding to resonances near the substrate Fermi level were found to be very close to their respective mono-electronic molecular orbitals. In contrast, high-order resonance states images were composed of molecular orbitals components from many states, even though those states lie in a lower energy range.