Jia Lin Zhang

Epitaxial Growth of Single Layer Blue Phosphorus: A New Phase of Two-Dimensional Phosphorus

Blue phosphorus, a previously unknown phase of phosphorus, has been recently predicted by theoretical calculations and shares its layered structure and high stability with black phosphorus, a rapidly rising two-dimensional material. Here, we report a molecular beam epitaxial growth of single layer blue phosphorus on Au(111) by using black phosphorus as precursor, through the combination of in situ low temperature scanning tunneling microscopy and density functional theory calculation. The structure of the as-grown single layer blue phosphorus on Au(111) is explained with a (4 × 4) blue phosphorus unit cell coinciding with a (5 × 5) Au(111) unit cell, and this is verified by the theoretical calculations. The electronic bandgap of single layer blue phosphorus on Au(111) is determined to be 1.10 eV by scanning tunneling spectroscopy measurement. The realization of epitaxial growth of large-scale and high quality atomic-layered blue phosphorus can enable the rapid development of novel electronic and optoelectronic devices based on this emerging two-dimensional material.

Electroless polyol deposition and magnetic properties of nanostructured Ni50Co50 films

The deposition of NiCo films with a nominal composition of 50:50 by a single-step, electroless polyol method was investigated. The film thickness increased with increasing deposition time from 5 to 60 min. Measured film compositions showed Ni: Co stoichiometry for films deposited at 5 and 60 min: In the intermediate range of deposition time used, deviation from nominal precursor concentration to Co-rich compositions was observed as a result of change in deposition chemistry. Through-thickness concentration gradient conceivably existed for thicker films as diffusion for compositional homogenization would not be significant at the deposition temperature. The apparent film density increased as a result of coalescence of adjacent particles with increasing film thickness. The particles consisted of nanostructured crystallites. The crystallite size did not significantly change with increasing deposition time, indicating no grain growth had occurred. Nanoscale particles were also observed among the larger partic...

Growth of Quasi-Free-Standing Single-Layer Blue Phosphorus on Tellurium Monolayer Functionalized Au(111)

Blue phosphorus, a newly proposed allotrope of phosphorus, represents a promising 2D material with predicted large tunable band gap and high charge-carrier mobility. Here, we report a simple method for the growth of quasi-free-standing single layer blue phosphorus on tellurium functionalized Au(111) by using black phosphorus as the precursor. In situ low-temperature scanning tunneling microscopy (LT-STM) measurements were used to monitor the growth of the single-layer blue phosphorus, which forms triangular structures arranged hexagonally on the tellurium layer. As revealed by in situ X-ray photoelectron spectroscopy, LT-STM measurements, and density functional theory calculation, the blue phosphorus layer weakly interacts with the underlying tellurium layer.

Single-Molecule Imaging of Activated Nitrogen Adsorption on Individual Manganese Phthalocyanine

An atomic-scale understanding of gas adsorption mechanisms on metal-porphyrins or metal-phthalocyanines is essential for their practical application in biological processes, gas sensing, and catalysis. Intensive research efforts have been devoted to the study of coordinative bonding with relatively active small molecules such as CO, NO, NH3, O2, and H2. However, the binding of single nitrogen atoms has never been addressed, which is both of fundamental interest and indeed essential for revealing the elementary chemical binding mechanism in nitrogen reduction processes. Here, we present a simple model system to investigate, at the single-molecule level, the binding of activated nitrogen species on the single Mn atom contained within the manganese phthalocyanine (MnPc) molecule supported on an inert graphite surface. Through the combination of in situ low-temperature scanning tunneling microscopy, scanning tunneling spectroscopy, ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations, the active site and the binding configuration between the activated nitrogen species (neutral nitrogen atom) and the Mn center of MnPc are investigated at the atomic scale.

Reversible Tuning of Interfacial and Intramolecular Charge Transfer in Individual MnPc Molecules

The reversible selective hydrogenation and dehydrogenation of individual manganese phthalocyanine (MnPc) molecules has been investigated using photoelectron spectroscopy (PES), low-temperature scanning tunneling microscopy (LT-STM), synchrotron-based near edge X-ray absorption fine structure (NEXAFS) measurements, and supported by density functional theory (DFT) calculations. It is shown conclusively that interfacial and intramolecular charge transfer arises during the hydrogenation process. The electronic energetics upon hydrogenation is identified, enabling a greater understanding of interfacial and intramolecular charge transportation in the field of single-molecule electronics.

Low-temperature scanning tunneling microscopy/ultraviolet photoelectron spectroscopy investigation of two-dimensional crystallization of C60: pentacence binary system on Ag(111)

Atomic scale investigation of temperature-dependent two-dimensional (2 D) crystallization processes of fullerene-C60 on pentacene-covered Ag(111) surface has been carried out by in situ low-temperature scanning tunneling microscopy (LT-STM) experiments. To evaluate the effect of molecule-substrate interfacial interactions on the 2 D crystallization of C60: pentacene binary system, we also carried out the same self-assembly experiments of C60 on monolayer pentacene covered graphite substrate. It is revealed that temperature-dependent structural transition of various ordered C60 nanoassemblies is strongly influenced by the molecule-Ag(111) interfacial interactions, and further mediated by the weak C60-pentacene intermolecular interactions. In situ ultraviolet photoelectron spectroscopy (UPS) has been used to evaluate the nature of the intermolecular interactions between C60 and pentacene films.

CHAPTER 3:Low-Dimensional Supramolecular Assemblies on Surfaces

Low-dimensional supramolecular architectures with well-defined arrangement and desired functionalities over macroscopic area are important building blocks for functional organic nanodevices as well as ideal model systems by which to investigate the working mechanism of molecular electronics at the atomic scale. This chapter discusses the construction of one-dimensional (1D) molecular chains and two-dimensional (2D) molecular networks involving single component or binary molecular building blocks based on the non-covalent interactions, including the hydrogen-bonding and metal–ligand coordination. We will also discuss the on-surface polymerization induced covalently bonded 1D molecular chains and 2D molecular networks.

2D Phosphorene: Epitaxial Growth and Interface Engineering for Electronic Devices

Black phosphorus (BP), first synthesized in 1914 and rediscovered as a new member of the family of 2D materials in 2014, combines many extraordinary properties of graphene and transition-metal dichalcogenides, such as high charge-carrier mobility, and a tunable direct bandgap. In addition, it displays other distinguishing properties, e.g., ambipolar transport and highly anisotropic properties. The successful application of BP in electronic and optoelectronic devices has stimulated significant research interest in other allotropes and alloys of 2D phosphorene, a class of 2D materials consisting of elemental phosphorus. As an atomically thin sheet, the various interfaces presented in 2D phosphorene (substrate/phosphorene, electrode/phosphorene, dielectric/phosphorene, atmosphere/phosphorene) play dominant roles in its bottom-up synthesis, and determine several key characteristics for the devices, such as carrier injection, carrier transport, carrier concentration, and device stability. The rational design/engineering of interfaces provides an effective way to manipulate the growth of 2D phosphorene, and modulate its electronic and optoelectronic properties to realize high-performance multifunctional devices. Here, recent progress of the interface engineering of 2D phosphorene is highlighted, including the epitaxial growth of single-layer blue phosphorus on different substrates, surface functionalization of BP for high-performance complementary devices, and the investigation of the BP degradation mechanism in ambient air.