Narrow Results

Poly(vinylidene fluoride) (PVDF, –(CH₂–CF₂)_n–) shows the effective H⁺ desorption induced by the irradiation of photon corresponding to the transition from carbon (C) 1s to σ(C–H)*. In order to clarify the effect of the C–H bond scission by the irradiation, near-edge X-ray absorption fine structure (NEXAFS) spectra and the kinetic energy (E_k) distribution of desorbed ion were observed. By the irradiation of photon near C 1s region, a new peak appears in the C 1s NEXAFS spectra at photon energy of 285 eV, which is about 3 eV lower than that of the lowest peak in the NEXAFS spectrum of the pristine PVDF film. The appearance of the lowest NEXAFS peak of irradiated PVDF film is assigned to the transition to π*. It indicates that the irradiation of photons near C 1s region introduces carbon–carbon double bonds into the backbone chain of PVDF. At early stage of X-ray exposure the yield of desorbed ion with low E_k (~ 2 eV) decreases rapidly. The ion with low E_k is assigned to H⁺ desorbed from the sp³-hybrid state, which is characteristics of the pristine PVDF. It indicates that formation of double bonds in PVDF backbone chain makes the number of sp³-hybrid state decrease. This variation occurs by irradiation of photons corresponding to the transition from C 1s to σ(C–H)* more rapidly than that to the transition to σ(C–F)*.

The discovery of two-dimensional (2D) materials with single or a few-atom-thick layers has presented unprecedented opportunities to study, control and harness the properties of van der Waals (vdW) materials at their 2D limit. It also offers a platform that allows the arbitrary creation of heterostructures in a materials-by-design approach with properties tailored by the constituting components. Combining organic molecules with 2D materials to form hybrid heterointerfaces has recently emerged as a facile and versatile approach to engineer the electronic, optical, magnetic and chemical properties of 2D materials for new or optimized device applications. Underpinning the development of organic–2D materials heterostructures is the ability to interrogate the interfacial electronic structures and properties at multiple dimensions. This review provides a timely update on the application of synchrotron-based soft X-ray spectroscopies (SR-SXS) in the characterization of organic–2D materials interfaces. By harnessing the unparalleled high energy resolution, tunable energy, high brilliance and tunable polarization inherent to synchrotron radiation, electronic structures, charge transfer dynamics, molecular orientations and spin configurations at the hybrid interfaces can be examined, which helps us to formularize a coherent understanding of the organic–2D materials interfaces that will guide the design of new hybrid vdW structures and devices. We also offer our perspective on the future application of SR-SXS in the exploration of organic–2D materials heterostructures.

This paper focuses on the use and value of XPS and NEXAFS spectroscopies to unveil the nature of the chemical bond of various bifunctional nitrile molecules adsorbed on Si(001) 2×1 at 300 K. The adsorption modes are also discussed in the light of recent theoretical publications devoted to optimized geometries and reaction paths of these molecules on Si(001).

Unveiling the interplay of semiconducting organic molecules with their environment, such as inorganic materials or atmospheric gas, is the first step to designing hybrid devices with tailored optical, electronic or magnetic properties. The present article focuses on a double-decker lutetium phthalocyanine known as an intrinsic semiconducting molecule, holding a Lu ion in its center, sandwiched between two phthalocyanine rings. Carrying out experimental investigations by means of electron spectroscopies, X-ray diffraction and scanning probe microscopies together with advanced ab initio computations, allows us to unveil how this molecule interacts with weakly or highly reactive surfaces. Our studies reveal that a molecule–surface interaction is evidenced when molecules are deposited on bare silicon or on gold surfaces together with a charge transferred from the substrate to the molecule, affecting to a higher extent the lower ring of the molecule. A new packing of the molecules on gold surfaces is proposed: an eclipse configuration in which molecules are flat and parallel to the surface, even for thick films of several hundreds of nanometers. Surprisingly, a robust tolerance of the double-decker phthalocyanine toward oxygen molecules is demonstrated, leading to weak chemisorption of oxygen below 100 K.

A series of polycrystalline bulk samples of Mn_1+xFe_2-2xTi_xO₄ (0 ≤ x ≤ 0.5) have been prepared by using a conventional solid-state reaction method. The effect of Ti⁴⁺ ions substitution on magnetic and electronic structure of MnFe₂O₄ has been studied using isothermal d.c. magnetization and near edge X-ray absorption fine structure spectroscopy (NEXAFS) measurements. The magnetization studies infer that all samples have ferrimagnetic ordering at room temperature. The magneton number (n_B) calculated using the magnetic hysteresis loop has been found to decrease linearly with the Ti substitution, which indicates that the system follows the Neel's two sub-lattice model. The decrease in the value of n_B may be due to the dilution of the sub-lattice by Ti ions. The NEXAFS measurements performed at Fe/Ti L_{3, 2} edges indicate that Fe ions are in mixed valence state whereas Ti ions remain unchanged at 4⁺ state.

We report structural, magnetic and electronic structure studies of pure and Cu doped ZnO nanorods with the aim to understand the origin of ferromagnetism. A structural study indicates that all the samples exhibit single phase nature and rules out the formation of secondary phase. NEXAFS measurements reveal that Cu ions exist in Cu²⁺ state. Magnetic hysteresis loop measurements reflect that the pure and Cu doped ZnO nanorods exhibit room temperature ferromagnetism. The increase in the intensity of green emission in photoluminescence study indicates that defects density increases with Cu doping.

The Pd nanoparticles were fabricated by the gas evaporation method without any capping molecules. It is found that the average diameter of the nanoparticles are 1.7 nm with standard deviation of 0.8 nm by AFM observations. The chemical states of the nanoparticles were measured by the in situ XPS. The XPS results indicate that the chemical states of the nanoparticles become almost the same as the bulk Pd. The chemical states of the air-exposed Pd nanoparticles were also observed by the ex situ XPS and NEXAFS methods. Both ex situ XPS and NEXAFS measurements indicate that the nanoparticles were naturally oxidized under an atmospheric environment. Considering from the behavior of Pd 3d XPS and the diameter of nanoparticles, it is suggested that the depth of oxidized Pd layer is less than 1.4 monolayer from the nanoparticles surface.

Unveiling the interplay of semiconducting organic molecules with their environment, such as inorganic materials or atmospheric gas, is the first step to designing hybrid devices with tailored optical, electronic or magnetic properties. The present article focuses on a double-decker lutetium phthalocyanine known as an intrinsic semiconducting molecule, holding a Lu ion in its center, sandwiched between two phthalocyanine rings. Carrying out experimental investigations by means of electron spectroscopies, X-ray diffraction and scanning probe microscopies together with advanced ab initio computations, allows us to unveil how this molecule interacts with weakly or highly reactive surfaces. Our studies reveal that a molecule–surface interaction is evidenced when molecules are deposited on bare silicon or on gold surfaces together with a charge transferred from the substrate to the molecule, affecting to a higher extent the lower ring of the molecule. A new packing of the molecules on gold surfaces is proposed: an eclipse configuration in which molecules are flat and parallel to the surface, even for thick films of several hundreds of nanometers. Surprisingly, a robust tolerance of the double-decker phthalocyanine toward oxygen molecules is demonstrated, leading to weak chemisorption of oxygen below 100 K.

The discovery of two-dimensional (2D) materials with single or a few-atom-thick layers has presented unprecedented opportunities to study, control and harness the properties of van der Waals (vdW) materials at their 2D limit. It also offers a platform that allows the arbitrary creation of heterostructures in a materials-by-design approach with properties tailored by the constituting components. Combining organic molecules with 2D materials to form hybrid heterointerfaces has recently emerged as a facile and versatile approach to engineer the electronic, optical, magnetic and chemical properties of 2D materials for new or optimized device applications. Underpinning the development of organic–2D materials heterostructures is the ability to interrogate the interfacial electronic structures and properties at multiple dimensions. This review provides a timely update on the application of synchrotron-based soft X-ray spectroscopies (SR-SXS) in the characterization of organic–2D materials interfaces. By harnessing the unparalleled high energy resolution, tunable energy, high brilliance and tunable polarization inherent to synchrotron radiation, electronic structures, charge transfer dynamics, molecular orientations and spin configurations at the hybrid interfaces can be examined, which helps us to formularize a coherent understanding of the organic–2D materials interfaces that will guide the design of new hybrid vdW structures and devices. We also offer our perspective on the future application of SR-SXS in the exploration of organic–2D materials heterostructures.

The following sections are included:

• Introduction

• NEXAFS Spectroscopy
  • Instrument Aspects of NEXAFS and Electron Energy Loss Spectroscopy
  • NEXAFS Spectroscopy of Polymers: Chemical Sensitivity
    • Chemical Sensitivity: Examples
  • NEXAFS Spectroscopy of Polymers: Orientational Sensitivity
  • NEXAFS Spectroscopy of Polymers: Quantitative Analysis
    • Blends of Polycarbonate and Poly(butylene terephthalate)
    • Quantitative Analysis of the Chemical Composition of Polyurethanes

• NEXAFS Microscopy: Instrumentation and Analysis Tools
  • Quantitative Image Analysis

• NEXAFS Microscopy: Applications
  • Surfaces and Thin Films
    • Polyimide Films and Surface
    • Overcoats and Lubricating Layers on Hard Disks
    • Confined, Free Standing Homopolymer Thin Films
    • Thin Film Blends
    • Thin Film Polymer Bilayers
    • Block Copolymer Thin Films
  • Bulk Morphology and Composition of Multicomponent, Multiphasic Polymers
    • NEXAFS Microscopy of Poly(ethylene terephthalate)/Vectra™ Blends
    • Engineered Polyurethane Polymers
    • Multilayers
    • Elastomer Composites
  • Fibers
  • Organic Geochemistry
  • Meteoritics and Interplanetary Dust Particles
  • Soils and Environmental Studies
  • Other Applications

• Summary and Future Outlook

• Acknowledgments

• References

The following sections are included:

• Introduction

• UV Photoelectron Spectroscopy (UPS)
  • Methodology
    • General and Experimental Aspects
    • Theoretical Analysis of UPS Spectra
    • Energy Band Mapping for One-Dimensional Systems
  • Electronic Structure of Molecular Solids
    • Density of States, Solid State Effect, and Angular Dependence
    • The Use of the Tunability of Synchrotron Radiation
    • Intermolecular Energy Band Mapping
  • Polymers and Oligomers
    • Density of States
    • Band Evolution in Oligomers
    • Intramolecular Energy Band Mapping
  • Electronic Structure of Binary Systems
    • Complexes
    • Interfaces
  • ARUPS as a Novel Probe of Molecular Orientation

• NEXAFS Spectroscopy
  • General and Experimental Aspects
  • Characteristics of Core Excitations
    • Selection Rules
    • Core Excitonic Effect
    • Spectral Assignments
    • Theoretical Simulation and Analysis
  • Molecular Orientation and Chemical States of π-Conjugated Systems
    • Molecules on Well Defined Surfaces
    • Other Studies of Molecules and Polymers in Various States
  • Electronic Structures of the Unoccupied States of π-Conjugated Systems
    • Aromatic Molecules
    • Fullerenes and Nanotube
    • Metal Complexes
    • π-Conjugated Polymers
    • Doping and Reactions
  • Alkanes and Compounds with Long Alkyl Chains
    • C K edge Absorption of Alkyl Chain
    • Compounds with Long Alkyl Chains
  • Other Polymers and Their Surfaces
    • Polymers with Fluorinated Chains
    • Silicon-Backboned Polymers
    • Polyimides and Their Rubbed States
    • Other Polymers
  • Other Applications

• Acknowledgments

• References

The following sections are included:

• Introduction

• Principle of Surface XAFS
  • NEXAFS Spectroscopy
  • SEXAFS Spectroscopy

• Experimental

• Application to Atomic Adsorbates
  • Surface Anisotropic Vibration and Anharmonicity
  • Coverage Dependence of Surface Chemical Bonding

• Application to Molecular Adsorbates
  • Thiophene on Ni(100), Cu(100) and Pd(100)
  • The Structures of SO₂ Adsorbed on Metals
  • Surface Chemical Reaction of SO₂ on Cu(100)
  • Alkanethiols Adsorbed on Cu(111) and Cu(100)

• Future Prospects

• Acknowledgments

• Appendix

• References