X-ray photoelectron emission studies of mixed selenides AgGaSe2 and Ag9GaSe6

Auger and direct electron specta from crystalline AgGaSe₂ and Ag₉GaSe₆ have been studied with X-ray photoelectron spectroscopy. It is shown that the AgM₅N_4,5N_4,5 and M₄N_4,5N_4,5 Auger spectra are more sensitive to the chemical environment than the Ag 3d direct photoelectron spectra. Furthermore the Auger parameter as defined by Wagner is used in order to characterize the chemical state of these compounds. Last, the XPS spectra of the valence-band region are investigated and chalcogen s and p and noble-metal d bands are clearly identified. The electronic structure of these two selenides does not seem to be determined predominantly by the crystal structure. As a whole, the spectral features are discussed in connection with the character of the chemical bonding and the physical properties of these compounds.     

A study of the spinel materials LiTi2O4 and Li43Ti53O4 by photoelectron spectroscopy

HeI-excited valence-band ultraviolet photoelectron spectra and MgKα-excited Ti-2p X-ray photoelectron spectra are reported for the spinel materials LiTi₂O₄ and $\text{Li}{}_{\mathrm{<mtext>4</mtext><mtext>3</mtext>}}\text{Ti}{}_{\mathrm{<mtext>5</mtext><mtext>3</mtext>}}\text{O}{}_4$. The presence of a Fermi edge in the ultraviolet photoelectron spectrum of LiTi₂O₄ confirms the metallic nature of this material, although the measured density of states at the Fermi energy is much lower than that expected from an independent-electron interpretation of the magnetic susceptibility. This difference is attributed to a strong interaction of the conduction electrons with the lattice vibrations. The localization of conduction electrons that occurs in the final state in the Ti-2p X-ray photoelectron spectrum of LiTi₂O₄ is attributed to a Coulomb interaction with a core hole.     

Facile synthesis of multifunctional multiwalled carbon nanotubes/Fe3O4 nanoparticles/polyaniline composite nanotubes

With an average diameter of 100-150 nm, composite nanotubes of polyaniline (PANI)/multiwalled carbon nanotubes (MWNTs) containing Fe₃O₄ nanoparticles (NPs) were synthesized by a two-step method. First, we synthesized monodispersed Fe₃O₄ NPs (d=17.6 nm, σ=1.92 nm) on the surface of MWNTs and then decorated the nanocomposites with a PANI layer via a self-assembly method. SEM and TEM images indicated that the obtained samples had the morphologies of nanotubes. The molecular structure and composition of MWNTs/Fe₃O₄ NPs/PANI nanotubes were characterized by Fourier transform infrared spectra (FTIR), energy dispersive X-ray spectrometry (EDX), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD) and Raman spectra. UV-vis spectra confirmed the existence of PANI and its response to acid and alkali. As a multifunctional material, the conductivity and magnetic properties of MWNTs/Fe₃O₄ NPs/PANI composites nanotubes were also investigated.     

A study of shake-up satellites in Co 2p photoelectron spectra of trans-[Co(NH3)4Cl2]Cl and cis-[Co(NH3)4Cl2]Cl isomers

Mg Kα X-ray photoelectron (ESCA) spectra of the Co 2p levels have been obtained in trans- and cis-[Co(NH₃)₄Cl₂]Cl isomers. It is observed that these compounds slowly decompose under X-ray irradiation. A procedure is employed to record real spectra for both the trans and cis isomers without any significant complication by the decomposition products. Three satellites are observed in both spectra at binding energies ≈ 4.8 eV, ≈ 9.3 eV, and ≈ 16.5 eV greater than that of the Co 2p_{$\text{3}\text{2}$} peak. These isomers are distinguished from one another by the sizable difference in the relative intensity of the first satellite to the main peak. The first two satellites are assigned to ligand to Co 3d shake-up transitions by use of symmetry arguments based on molecular orbital theory, while the origin of the third satellite is less certain. The implication of the results is discussed.     

Allylic interactions in organometallics: probing Electronic structure in (η5-C5H5)Fe(CO)2R,R = CH3, η1-C3H5, η1-C5H5.

The He(I) photoelectron spectra of (η⁵-C₅H₅)Fe(CO)₂R, where R = CH₃, η¹-C₃H₅ and η¹-C₅H₅, have been recorded. The lowest lying ion states result from ionization of molecular orbitals with large Fe 3d character; these move to lower anergy when R places double bonds in an allylic relationship to the metal atom. The cyclic voltammetric oxidation potential correlates well with the energies of the lowest ion states. A significant interaction between olefin π orbitals and the allylic metal center is proposed.     

Ultra-Shallow Chemical Characterization of Organic Thin Films Deposited by Plasma and Vacuum-Ultraviolet, Using Angle- and Excitation Energy-Resolved XPS

Nitrogen (N)-rich organic thin films were deposited using both low-pressure plasma- and vacuum-ultraviolet-based techniques, from mixtures of ammonia (NH₃) and ethylene (C₂H₄). These films were investigated using angle-resolved and excitation energy resolved X-ray photoelectron spectroscopy (ARXPS and ERXPS, respectively) in order to determine their sub-surface chemical profiles. These two techniques enable one to tune the ??XPS 95%?? information depth, z _95%, by varying either the angle or the excitation energy. Using a combination of both techniques, z _95% can be varied continuously from 0.7 to 11 nm. The surface-near chemistry is investigated using both high-resolution C 1s spectra and elemental concentrations derived from elemental peak intensities. Results show that while laboratory XPS, and even ARXPS, suggest homogenous surface chemistries, the novel combination of ARXPS and ERXPS points to the existence of a compositional profile in the extreme outer surface layer. Our conclusions are supported by simulations using SESSA software.     

Shake-up satellites in Hel photoelectron spectra: N2O4 and CH3O

Low-lying vacant molecular orbitals may lead not only to a breakdown of Koopmans' theorem but also to satellite structure in photoelectron spectra. This paper reports examples of the relatively infrequent appearance of shake-up satellites in Hel photoelectron spectra, namely those of N₂O₄ and CH₃NO. An extended version of the HAM/3 program was used to interpret these spectra.     

A Novel in Situ Oxidization-Sulfidation Growth Route via self-Purification Process to β-In2S3 Dendrites

A novel in situ oxidization-sulfidation growth route via a self-purification process has been developed to synthesize β-In₂S₃ dendrites. To our best knowledge, this is the first example to prepare dendrites of III-VI compounds, which are expected to show particular physical properties. The X-ray analysis (EDXA), X-ray photoelectron spectra (XPS), Raman spectrum and optical properties of β-In₂S₃ dendrites have also been investigated. It is found that the product is pure In₂S₃ and shows the strong quantum confinement of the excitonic transition expected for the In₂S₃ dendrites.     

Preparation and characterization of the nanoporous ultrathin multilayer films based on molybdenum polyoxometalate (Mo38)n

Ultrathin multilayer films of the wheel-shaped molybdenum polyoxometalate cluster (Mo₃₈)_n and poly(allylamine hydrochloride)(PAH) have been prepared by the layer-by-layer (LbL) self-assembly method. The ((Mo₃₈)_n/PAH)_m multilayer films have been characterized by X-ray photoelectron spectra (XPS) and atomic force microscopy (AFM). UV-VIS measurements reveal regular film growth with each (Mo₃₈)_n adsorption. The electrochemistry behavior of the film at room temperature was investigated.     

Ab initio configuration interaction calculations of the NIs (NO2) core-hole states of p-nitroaniline

The NIs (NO₂) core-hole states of p-nitroaniline are calculated by a Cl procedure that takes account of both orbital relaxation and correlation effects. A satellite peak arising from the excitation 4b₁(Π) → 5b₁(Π) is calculated to occur 26 eV from the main ionization peak, with a relative intensity of 66%. These results are compared with gas-phase photoelectron spectra.     

The TS0 transitions and molecular conformations of p-terphenyl

The T ← S_o absorption spectra of a p-terphenyl (TP) crystal at 77 K and room temperature were measured. These spectra were compared with the T ← S_o absorption and phosphorescence spectra of TP in solution. The comparison of these spectra gave some information about the potential curves of TP molecules as a function of the angle between the outer and central benzene rings both in the triplet and ground state.     

Approach to thermal properties and electronic polarizability from average single bond strength in ZnOBi2O3B2O3 glasses

The glass transition temperature (T_g), density, refractive index, Raman scattering spectra, and X-ray photoelectron spectra (XPS) for xZnO-yBi₂O₃-zB₂O₃ glasses (x=10-65, y=10-50, z=25-60 mol%) are measured to clarify the bonding and structure features of the glasses with large amounts of ZnO. The average electronic polarizability of oxide ions (α_O2−) and optical basicity (Λ) of the glasses estimated using Lorentz-Lorenz equation increase with increasing ZnO or Bi₂O₃ content, giving the values of α_O2−=1.963 Å³ and Λ=0.819 for 60ZnO-10Bi₂O₃-30B₂O₃ glass. The formation of BOBi and BOZn bridging bonds in the glass structure is suggested from Raman and XPS spectra. The average single bond strength (B_MO) proposed by Dimitrov and Komatsu is applied to the glasses and is calculated using single bond strengths of 150.6 kJ/mol for ZnO bonds in ZnO₄ groups, 102.5 kJ/mol for BiO bonds in BiO₆ groups, 498 kJ/mol for BO bonds in BO₃ groups, and 373 kJ/mol for BO bonds in BO₄ groups. Good correlations are observed between T_g and B_MO, Λ and B_MO, and T_g and Λ, proposing that the average single bond strength is a good parameter for understanding thermal and optical properties of ZnOBi₂O₃B₂O₃ glasses.     

Atomic and chemical effects in Sm and Sm2O3 photoelectron spectra

We present here a comparative study of Sm and Sm₂O₃ photoelectron spectra. They are well interpreted by atomic effects, except the Sm₂O₃ d spectra which exhibit chemical effects.     

Next-nearest neighbour contributions to P 2p3/2 X-ray photoelectron binding energy shifts of mixed transition-metal phosphides M1−xM′xP with the MnP-type structure

X-ray photoelectron (XPS) and X-ray absorption (XANES) spectroscopic measurements have been made for several series of mixed transition-metal phosphides M_1−xM′_xP (Co_1−xMn_xP, Mn_1−xV_xP, and Co_1−xV_xP), which adopt the MnP-type structure (M is more electronegative than M′). The P 2p binding energy shifts displayed by the mixed metal phosphide members do not follow the trend shown by the simple binary phosphides, a deviation which arises from the contribution of next-nearest neighbour effects operating on the primary photoemission site. The magnitude of this contribution can be derived from a simple charge potential model taking the metal electronegativity differences into account. It is suggested that these next-nearest neighbour contributions induce a charge transfer between the two dissimilar metals via metal-metal bonding, which modifies the Madelung potential experienced at the photoemission site. This charge transfer has been confirmed by analysis of the Co 2p XPS spectra as well as the P and Mn K-edge XANES spectra.     

Ex-situ XPS-investigation of the interface between PE-CVD SiO2 and wet chemically etched MO-CVD epitaxial layers of In0.53Ga0.47As

The As rich SiO₂/In_0.53Ga_0.47As interface which is produced by wet chemical etching before SiO₂ deposition to improve the electronic properties of the interface has been studied. SiO₂-layers of about 10 to 20 nm thickness have been deposited in a plasma enhanced chemical vapour deposition (PECVD) reactor and then thinned down to about 4 to 3 nm by 1.5 keV Ar ion beam bombardment at grazing incidence (85°) in the XPS analysis chamber. The photoelectron spectra show that an additional broadening of the In and As lines due to a possible ion beam damage can be neglected in case of a qualitative interpretation of the interface spectra. Moreover, TRIM simulations of the collision cascade reveal low damage production in the SiO₂/In_0.53Ga_0.47As interface region. Therefore such ex-situ XPS experiments allow a supervision of the interface chemistry after the fabrication process and an optimisation of the technology with regard to the etching solution and deposition conditions. The conservation or removal of the elemental arsenic and the oxidation of the semiconductor due to the SiO₂ deposition are well reflected in the photoelectron spectra.     

The photoelectron and microwave spectra of the unstable species thioacetaldehyde,CH3CHS,and thioacetone, (CH3)2CS

Combined photoelectron and microwave techniques have been used to study the unstable species thioacetaldehyde, CH₃CHS, and thioacetone, (CH₃)₂CS. These species are produced when their respective cyclic trimers, 1,3,5-trimethyl s-trithiane and hexamethyl s-trithiane, are pyrolysed. The trimer vapours are flowed at approximately 30 μ Hg pressure via a quartz tube heated to between 500 and 600°C into a photoelectron or microwave spectrometer. Under these low pressure conditions the lifetime of CH₃CHS was about 10 seconds. The lifetime of (CH₃)₂CS was much longer, of the order of several minutes.The first (vertical) ionisation potentials of thioacetaldehyde and thioacetone are 8.98 ± 0.02 eV and 8.60 ± 0.05 eV respectively. The photoelectron spectra of the parent trimers have also been studied as well as s-trithiane, the trimer of thioformaldehyde. The microwave rotational spectra show evidence of hindered internal rotation. Preliminary analyses indicate that in thioacetaldehyde the barrier is 1545 ± 20 cal per mole (6470 joule per mole) and in thioacetone it is 1300 ± 50 cal per mole (5440 joule per mole).     

The identification and differentiation between the polarised photoelectron,e−photo and the loose ion pair, (Rb+, e) in Rb—THF solution

An optical—ESR study in Rb—THF solutions, containing varying concentrations of crown ether and p-xylene, is presented. Two paramagnetic species are identified in terms of their chemical reactivity and their ESR spectra: the polarized photoelectron, e^-_photo, and the loose ion pair, (Rh⁺, e), which is observed in a Boltzmann distribution.     

Synthesis, structures and photocatalytic activities of microcrystalline ABi2Nb2O9 (A=Sr, Ba) powders

Microcrystalline ABi₂Nb₂O₉ (A=Sr, Ba) photocatalysts were successfully synthesized by a citrate complex method. The as-prepared samples were characterized by the X-ray diffraction technique, BET surface area analysis, UV-vis diffuse reflectance spectrum, transmission electron microscopy, X-ray photoelectron spectroscopy and inductively coupled plasma-atomic emission spectrometry. The results indicated that single-phase orthorhombic SrBi₂Nb₂O₉ could be obtained after being calcined above 650 °C, while BaBi₂Nb₂O₉ was tetragonal. Based on the diffuse reflectance spectra, the band gaps of the obtained samples were calculated to be around 3.34-3.54 eV. For the photocatalytic redox reaction of methyl orange under UV-light irradiation, SrBi₂Nb₂O₉ exhibited higher photocatalytic activity than that of BaBi₂Nb₂O₉. The effects of the crystallinities, BET surface areas and crystal structures of the samples on the photocatalytic activities were discussed in detail.     

Observation of X1A1 vinylidene by photoelectron spectroscopy of the C2H2− ion

Photoelectron spectra of the vinylidene anion (C₂H₂^?) show vibrational structure in X¹A₁ vinylidene up 12 kcal/ mol above the vibrational ground state. Analysis yields an EA(C₂H₂$\text{X}$¹ A₁) of 0.47 ± 0.02 eV, and frequencies for the CC stretch and HCH bend. Absence of the ³B₂ state in the photoelectron spectra indicates the ¹A₁-³B₂ splitting in vinylidene is ? 1.7 eV.     

Preparation and characterization of shuttle-like α-Fe2O3 nanoparticles by supermolecular template

Shuttle-like α-Fe₂O₃ nanoparticles have been successfully synthesized via a new soft-template route using polyethylene glycol (PEG) as polymer, cetyltrimethylammonium bromide (CTAB) as surfactant and FeCl₃·6H₂O as iron source materials. Meanwhile, spherical α-Fe₂O₃ nanoparticles are also fabricated under the similar conditions without surfactant and polymer. The resultant products are characterized by means of thermalgravimetric analysis (TGA), powder X-ray diffraction (XRD), infrared (IR) spectroscopy, transmission electron micrograph (TEM), X-ray photoelectron spectra (XPS) and magnetization measurements. The homogeneous α-Fe₂O₃ nanoparticles with shuttle-like shape have an average length of 120 nm and a mean diameter of about 50 nm in the middle part (an average aspect ratio of about 2.5) whereas spherical α-Fe₂O₃ nanoparticles have a mean particle diameter of about 35 nm. Magnetic hysteresis measurements reveal that shuttle-like α-Fe₂O₃ nanoparticles display normal ferromagnetic behaviors while spherical α-Fe₂O₃ nanoparticles exhibit weak ferromagnetic behaviors at room temperature. The two types of α-Fe₂O₃ exhibit hysteretic features with the remanence and coercivity of 0.156 emu/g and 664 Oe, 0.048 emu/g and 110 Oe, respectively. The higher remanent magnetization and coercivity of shuttle-like α-Fe₂O₃ nanoparticles may be associated with the aspect ratio of α-Fe₂O₃ since shape anisotropy would exert a tremendous influence on their magnetic properties.